IPAC2019 - List of Keywords (simulation)

Paper	Title	Other Keywords	Page
MOPGW003	Collective Instability Studies for Sirius	impedance, storage-ring, radiation, coupling	61
	F.H. de Sá LNLS, Campinas, Brazil
	In this work we will present the estimates of single and multi-bunch instability thresholds and current-dependent effects, such as tune-shifts and potential-well distortion for the Sirius storage ring. The results were obtained by tracking simulations and semi-analytic methods using the updated and detailed impedance budget of the machine, which includes contributions from all the in-vacuum components and the coherent synchrotron radiation (CSR) impedance.
DOI •	reference for this paper ※ https://doi.org/10.18429/JACoW-IPAC2019-MOPGW003
About •	paper received ※ 15 May 2019 paper accepted ※ 18 May 2019 issue date ※ 21 June 2019
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MOPGW012	Study of Fringe Fields Effects from Final Focus Quadrupoles on Beam Based Measured Quantities	quadrupole, multipole, optics, dynamic-aperture	90
	T. Pugnat, B. Dalena CEA-IRFU, Gif-sur-Yvette, France L. Bonaventura, A. Simona Politecnico di Milano, Milano, Italy R. De Maria, V.K.B. Olsen CERN, Geneva, Switzerland
	Accelerator physics needs advanced modeling and simulation techniques, in particular for beam stability studies. A deeper understanding of the effects of magnetic fields non-linearities will greatly help in the improvement of future colliders design and performance. In , a new tracking method was proposed to study the effect of the longitudinal dependency of the harmonics on the beam dynamics. In this paper, the study will focus on the effects on observable quantities in beam based measurements, for the case of HL-LHC Inner Triplet and with possible tests in LHC. T. Pugnat et al., "Accurate and Efficient Tracking in Electromagnetic Quadrupoles", in Proc. IPAC’18, Vancouver, Canada, June 2018, paper THPAK004, pp. 3207.
DOI •	reference for this paper ※ https://doi.org/10.18429/JACoW-IPAC2019-MOPGW012
About •	paper received ※ 14 May 2019 paper accepted ※ 22 May 2019 issue date ※ 21 June 2019
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MOPGW019	Beam-Beam Blowup Issue After Low Emittance Tuning for FCC-ee	emittance, lattice, optics, coupling	112
	D. El Khechen, K. Oide, F. Zimmermann CERN, Geneva, Switzerland K. Oide KEK, Ibaraki, Japan
	FCC-ee (Future Circular Collider) is a 100 km electron-positron circular collider with two foreseen experiments, aiming to run at four energies for precision studies of the Z, W, and Higgs boson and the top quark. The FCC-ee is a challenging machine from different points of view. In particular the beam-beam effects are of great importance. For the FCC-ee high-luminosity operation, the beam-beam effects impose profound constraints on the operating point in betatron tune space. In addition, taking into account different sources of machine nonlinearities, a tracking simulation with beam-beam elements revealed a strong beam blowup, especially in the vertical plane. Such a blowup is a potential obstacle to achieving and maintaining a high luminosity; therefore it needs to be carefully studied. In this paper, we present a general overview of simulation results on the FCC-ee beam-beam blowup with realistic machine errors.
DOI •	reference for this paper ※ https://doi.org/10.18429/JACoW-IPAC2019-MOPGW019
About •	paper received ※ 10 May 2019 paper accepted ※ 20 May 2019 issue date ※ 21 June 2019
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MOPGW025	Beam Breakup Simulations for the Mainz Energy Recovering Superconducting Accelerator MESA	cavity, HOM, cryomodule, operation	135
	C.P. Stoll, F. Hug KPH, Mainz, Germany
	Funding: This work is supported by DFG through PRISMA+ cluster of excellence EXC 2118/2019, RTG 2128 and by the European Union’s Horizon 2020 Research and Innovation programme under Grant Agreement No 730871. MESA is a two pass energy recovery linac (ERL) currently under construction at the Johannes Gutenberg-University in Mainz. MESA uses four 1.3 GHz TESLA type cavities with 12.5 MV/m of accelerating gradient in two modified ELBE type cryomodule with improved thermal connection of the HOM antennas and cw operation. In the first stage of MESA operation 1mA of beam current is foreseen, which will later be upgraded to 10mA. One potential limit to maximum beam current in ERLs is the transverse beam breakup (BBU) instability induced by dipole Higher Order Modes (HOMs). These modes can be excited by bunches passing through the cavities off axis. Following bunches are then deflected by the HOMs, which results in even larger offsets for recirculated bunches. This feedback can even lead to beam loss. Simulation results for HOM spectra of a single TESLA cavity are available for example in . It was possible to measure the HOM spectra in the cold, not tuned cavities at DESY and in the cold string tuned to the 1.3 GHz fundamental mode at Mainz. Results for the maximum beam current for MESA, limited by BBU, for the various HOM spectra are presented. "Eigenmode Calculations for the TESLA Cavity Considering Wave-Propagation Losses through Fundamental and Higher-Order Mode Couplers", W. Ackermann, H. De Gersem, C. Liu, and T. Weiland
DOI •	reference for this paper ※ https://doi.org/10.18429/JACoW-IPAC2019-MOPGW025
About •	paper received ※ 16 April 2019 paper accepted ※ 20 May 2019 issue date ※ 21 June 2019
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MOPGW026	Transfer Line Optics Design Using Machine Learning Techniques	target, quadrupole, optics, operation	139
	D.M. Vilsmeier IAP, Frankfurt am Main, Germany M. Bai, M. Sapinski GSI, Darmstadt, Germany
	Optimization of transfer line optics is essential for delivering high quality beams to the experimental areas. This type of optimization is usually done by hand and relies on the experience of operators. The nature of this task is repetitive though highly complex. Besides optimizing the beam quality at the experiments this task is often accompanied by secondary objectives or requirements such as keeping the beam losses below an acceptable threshold. In the past years Deep Learning algorithms have experienced a rapid development and gave rise to various advanced software implementations which allow for straightforward usage of corresponding techniques, such as automatic differentiation and gradient backpropagation. We investigate the applicability and performance of these techniques in the field of transfer line optics optimization, specifically for the HADES beamline at GSI, in form of gradient-based differentiable simulators. We test our setup on results obtained from MADX simulations and compare our findings to different gradient-free optimization methods. Successfully employing such methods relieves operators from the tedious optimization tasks.
DOI •	reference for this paper ※ https://doi.org/10.18429/JACoW-IPAC2019-MOPGW026
About •	paper received ※ 15 May 2019 paper accepted ※ 20 May 2019 issue date ※ 21 June 2019
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MOPGW030	New Analytical Derivation of Group Velocity in TW Accelerating Structures	cavity, dipole, polarization, coupling	155
	M. Behtouei, M. Migliorati, L. Palumbo Sapienza University of Rome, Rome, Italy L. Faillace Universita’ degli Studi di Milano & INFN, Milano, Italy B. Spataro INFN/LNF, Frascati, Italy
	Ultra high-gradient accelerating structures are needed for the next generation of compact light sources. In the framework of the Compact Light XLS project, we are studying a high harmonic traveling-wave accelerating structure operating at a frequency of 35.982 GHz, in order to linearize the longitudinal space phase. In this paper, we propose a new analytical approach for the estimation of the group velocity in the structure and we compare it with numerical electromagnetic simulations that are carried out by using the code HFSS in the frequency domain.
DOI •	reference for this paper ※ https://doi.org/10.18429/JACoW-IPAC2019-MOPGW030
About •	paper received ※ 08 April 2019 paper accepted ※ 20 May 2019 issue date ※ 21 June 2019
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MOPGW035	Coupling Impedance of the Collimator Without RF-Shields at the RCS in J-PARC	impedance, synchrotron, collimation, proton	163
	Y. Shobuda, J. Kamiya, K. Moriya, K. Okabe JAEA/J-PARC, Tokai-Mura, Naka-Gun, Ibaraki-Ken, Japan
	All holes on the chamber walls of synchrotrons should be filled with the radiofrequency (RF)-shields to suppress coupling impedances that excite beam instabilities. In a synchrotron, titanium nitride (TiN)-coated RF-shields are installed with collimators. If the holes, through which the collimator jaw enters and exits the chamber, are filled with such RF-shields, the shields may break down as the dynamic coefficient of TiN increases in vacuum. At the Rapid Cycling Synchrotron (RCS), the RF-shields are eliminated from the collimator after demonstrating that the effect due to the RF-shields is negligible on the impedance at low frequencies.
DOI •	reference for this paper ※ https://doi.org/10.18429/JACoW-IPAC2019-MOPGW035
About •	paper received ※ 28 April 2019 paper accepted ※ 18 May 2019 issue date ※ 21 June 2019
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MOPGW037	Dynamic Variation of Chromaticity for Beam Instability Mitigation in the 3-GeV RCS of J-PARC	emittance, extraction, injection, impedance	171
	P.K. Saha, H. Harada, H. Hotchi, Y. Shobuda, T. Takayanagi, F. Tamura, Y. Watanabe JAEA/J-PARC, Tokai-Mura, Naka-Gun, Ibaraki-Ken, Japan
	We have studied many other dynamic approaches from that reported in the IPAC 2018 for transverse beam instability mitigation in the presence of strong space charge in the 3-GeV RCS of J-PARC. One of such a method is the introduction of an excess of chromaticity from that of natural chromaticity by reversing the sextupole magnetic fields from the middle of the acceleration cycle. The benifits of this method are twofold. It allows to utilize sextupole for chromaticty correction at lower energy and also mitigate the beam instability at higher energy because of introducing higher chromaticity. We first carried out numerical simulations by using ORBIT code, experimentally verified and then applied for the machine operation. The detail of simulation and measurements results are presented in this paper.
DOI •	reference for this paper ※ https://doi.org/10.18429/JACoW-IPAC2019-MOPGW037
About •	paper received ※ 14 May 2019 paper accepted ※ 23 May 2019 issue date ※ 21 June 2019
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MOPGW038	Collimator’s Impact Into the Transverse Emittance Growth at KEK Compact ERL	wakefield, emittance, operation, FEL	174
	O.A. Tanaka, T. Miyajima, N. Nakamura, T. Obina, M. Shimada, Y. Tanimoto KEK, Ibaraki, Japan
	In high-intensity particle accelerators, unwanted trans-verse and longitudinal wakefields arise when the high-charge particle beam passes through the narrow chambers or locations with small transverse apertures, such as collimator jaws. Transverse wakefields impose a transverse kicks to the beam, changing its shape, and leading to the growth of the transverse emittance. Longitudinal wakes cause the beam energy losses, heating of the narrow chambers etc. In the present study we investigated the collimator’s impact to the beam. Thus, we evaluated the collimator’s wakefields through the CST simulations. We estimated the corresponding transverse kicks and longitudinal wakes. In the summary simulation results were cross-checked with correspondent analytical expressions.
DOI •	reference for this paper ※ https://doi.org/10.18429/JACoW-IPAC2019-MOPGW038
About •	paper received ※ 15 May 2019 paper accepted ※ 21 May 2019 issue date ※ 21 June 2019
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MOPGW047	Analysis and Simulation of the "After-Pulse" RF Breakdown	cavity, timing, GUI, experiment	196
	X. Lin, H.B. Chen, Z.N. Liu, J. Shi, H. Zha TUB, Beijing, People’s Republic of China X.W. Wu CERN, Meyrin, Switzerland
	During the high power experiment of a single-cell standing-wave accelerating structure, it was observed that many RF breakdowns happen when the field inside cavity is decaying after the input rf pulse is off. The distribution of breakdown timing shows a peak at the moment of RF power switches off. A series of simulation was performed to study the after-pulse breakdown effect in such a standing-wave structure. A method of calculating poynting vector over time is proposed in this article to study the modified poynting vector at critical points in the cavity. Field simulation and thermal simulation were also carried out to analyse possible reasons for the after-pulse breakdown effect.
DOI •	reference for this paper ※ https://doi.org/10.18429/JACoW-IPAC2019-MOPGW047
About •	paper received ※ 14 May 2019 paper accepted ※ 17 May 2019 issue date ※ 21 June 2019
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MOPGW052	The Study of Single-Bunch Instabilities in the Ramping Process in the HEPS Booster	booster, impedance, lattice, injection	206
	H.S. Xu, Y.M. Peng, N. Wang IHEP, Beijing, People’s Republic of China
	The booster of High Energy Photon Source (HEPS) is proposed to ramp the beam energy from 500 MeV to 6 GeV, and to deliver the required charge to the storage ring. However, the transverse single-bunch instability may limit the reachable bunch charge in the booster. The study of the transverse single-bunch instability has been carried out for the HEPS booster at both 500 MeV and 6 GeV to double check whether the required single-bunch charge can be achieved. Furthermore, the energy ramping process was recently included in the study. We concentrate in the analyses of the simulation results with the consideration of energy ramping process in this paper.
DOI •	reference for this paper ※ https://doi.org/10.18429/JACoW-IPAC2019-MOPGW052
About •	paper received ※ 15 May 2019 paper accepted ※ 20 May 2019 issue date ※ 21 June 2019
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MOPGW062	Radiation of a Charge Moving in a Wire Structure	radiation, FEL, lattice, electron	231
	S.N. Galyamin, A.V. Tyukhtin, V.V. Vorobev Saint Petersburg State University, Saint Petersburg, Russia A.I. Benediktovitch EuXFEL, Hamburg, Germany A.I. Benediktovitch BSU, Minsk, Belarus, Belarus
	Funding: This work is supported by the grant from Russian Foundation for Basic Research (No. 17-52-04107). In the X-ray frequency region, interaction of relativistic electrons with crystals results in parametric X-ray radiation (PXR), with its frequency being determined by distance between crystallographic planes and direction of electron motion. If instead of crystal one considers an artificial periodic structure with periods of the order of mm, one can expect emission of radiation of a similar nature at terahertz (THz) frequencies. This frequency range is of significant interest during last decade due to its prospective applications. Moreover, artificial wire-like structures are considered as a promising alternative to conventional dielectric structures for wakefield acceleration. Here we consider electromagnetic (EM) field produced by a charged particle bunch moving through a lattice of parallel conducting wires. We present several approaches for analysis of EM field in the described wire structure. First, conventional two-wave approximation for describing the "short-wave response" is developed. Second, we use the effective medium approach and describe the "long-wave" part of the spectrum. Third, we develop a method based on vibrator antenna theory which can be useful for finite length wire structure. P.D. Hoang, et al., Phys. Rev. Lett., V. 120, P. 164801 (2018).
DOI •	reference for this paper ※ https://doi.org/10.18429/JACoW-IPAC2019-MOPGW062
About •	paper received ※ 14 May 2019 paper accepted ※ 20 May 2019 issue date ※ 21 June 2019
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MOPGW066	Local Impedance Measurements Using the Orbit Bump Method at ALBA	impedance, storage-ring, betatron, vacuum	240
	Z. Martí, G. Benedetti, T.F.G. Günzel, U. Iriso ALBA-CELLS Synchrotron, Cerdanyola del Vallès, Spain
	The orbit bump technique has been used at the ALBA Storage Ring to characterize with good precision the impedance of single machine elements, like the in-vacuum undulators or the CLIC stripline kicker. The results are compared with theoretical studies, as well as impedance measurements done at ALBA using other methods like the turn by turn betatron phase or from the analysis of the detuning slopes of the Transverse Mode Coupling Instability.
DOI •	reference for this paper ※ https://doi.org/10.18429/JACoW-IPAC2019-MOPGW066
About •	paper received ※ 14 May 2019 paper accepted ※ 17 May 2019 issue date ※ 21 June 2019
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MOPGW067	On Coordinate Systems in Beam Dynamics	GUI, experiment, acceleration, FEL	243
	E. Laface ESS, Lund, Sweden
	Any description of the beam dynamics calculation and simulation relies on the proper choice of a coordinate system in order to minimize the computational complexity and to apply different level of approximations in the calculations. This need generates a large number of reference systems, especially to describe the longitudinal dynamics of a particle beam like(z, z′),(t,∆P/P),(z, φ), etc. In this paper we summarize the rules to change coordinates systems, which system is canonical and how the Hamiltonian of the beam transforms according to the chosen coordinate system.
DOI •	reference for this paper ※ https://doi.org/10.18429/JACoW-IPAC2019-MOPGW067
About •	paper received ※ 10 May 2019 paper accepted ※ 20 May 2019 issue date ※ 21 June 2019
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MOPGW068	Crosstalk of Beam-Beam Effect and Longitudinal Impedance at CEPC	impedance, luminosity, collider, factory	247
	Y. Zhang, N. Wang, C.H. Yu IHEP, Beijing, People’s Republic of China C.T. Lin University of Chinese Academy of Sciences, Beijing, People’s Republic of China
	Funding: Project 11775238 supported by NSFC In conventional e⁺e⁻ storage ring colliders, we only use lengthend bunch length in beam-beam simulation instead of considering impedance directly. It is no problem since the longitudinal dynamics is not sensitive to beam-beam interaction. But it is different since the bunch will also be lengthend during beam-beam interaction by beamstrahlung effect. It is very natural and more self-consistent to consider the longitudinal impedance in the beam-beam simulation. The simulation shows that the working point region of stable collision is slightly shifted by the longitudinal impedance. It is found that the vertical coherent oscillation may decreases the beam-beam limit with impedance at some working point.
DOI •	reference for this paper ※ https://doi.org/10.18429/JACoW-IPAC2019-MOPGW068
About •	paper received ※ 15 May 2019 paper accepted ※ 20 May 2019 issue date ※ 21 June 2019
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MOPGW070	Longitudinal Stability of the Hollow Ion Bunches After Momentum Slip-Stacking in the CERN SPS	emittance, damping, synchrotron, proton	254
	T. Argyropoulos, A. Lasheen, D. Quartullo, E.N. Shaposhnikova CERN, Geneva, Switzerland
	Momentum slip-stacking is planned to be used for the lead ion beams in the CERN SPS to double the beam intensity for the High-Luminosity LHC project. During this RF manipulation two SPS batches, controlled by two independent RF systems, are going to be interleaved on an intermediate energy plateau, reducing the bunch spacing from 100 to 50 ns. However, there are limitations how close the frequencies of two RF systems can approach each other, resulting in a hole in the longitudinal bunch particle distribution due to the offset in energy of the recaptured bunches. After filamentation, these bunches should be further accelerated to the SPS top energy, before extraction to the LHC. Macro-particle simulations have shown that Landau damping is lost for the bunches with the smallest longitudinal emittances in the batch, causing un-damped oscillations of the bunch core after recapture. The standard application of an additional, fourth harmonic RF system, successfully used in proton operation, was not able to damp the oscillations at top energy, while it was necessary to switch it on from the moment of recapture. In this paper the longitudinal stability of the bunches after slip-stacking is studied in more details both by macro-particle simulations and analytical calculations.
DOI •	reference for this paper ※ https://doi.org/10.18429/JACoW-IPAC2019-MOPGW070
About •	paper received ※ 15 May 2019 paper accepted ※ 22 May 2019 issue date ※ 21 June 2019
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MOPGW073	Beam Manipulation Using Self-Induced Fields at the SwissFEL Injector	FEL, electron, experiment, wakefield	266
	S. Bettoni, P. Craievich, E. Ferrari, R. Ganter, F. Marcellini, E. Prat, S. Reiche PSI, Villigen PSI, Switzerland A.A. Lutman SLAC, Menlo Park, California, USA G. Penco Elettra-Sincrotrone Trieste S.C.p.A., Basovizza, Italy
	In the past years wakefield sources have been used to manipulate electron beams in accelerators. We recently installed corrugated structures for a total length of 2~m at the SwissFEL injector to test novel schemes for beam manipulations. We present simulations and early experimental results. We compare the model predictions with the measured data for the bunch energy losses and the kick factor, and show early results for the longitudinal phase space linearization and the production of current spikes.
DOI •	reference for this paper ※ https://doi.org/10.18429/JACoW-IPAC2019-MOPGW073
About •	paper received ※ 09 May 2019 paper accepted ※ 20 May 2019 issue date ※ 21 June 2019
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MOPGW076	Verification by RF Measurements of New HOM Mitigation Scheme Developed for Future SPS 33-Cell Accelerating Structures	HOM, damping, impedance, coupling	274
	P. Kramer, A. Farricker, C. Vollinger CERN, Geneva, Switzerland
	Longitudinal higher-order modes (HOMs) at a frequency of around 630 MHz in the 200 MHz travelling wave RF structures currently limit the beam intensities in the CERN SPS to less than that required by the High Luminosity (HL-) LHC. In the framework of the LHC Injectors Upgrade (LIU) project, the performance of the already existing HOM damping scheme for these standing wave modes must be improved. This involves improving the existing HOM-couplers as well as the possible use of a new mitigation technique via the insertion of resonant posts in some cells of the multi-cell structures. The development of the new damping scheme has been performed using theoretical analysis of the cavity-coupler interaction in conjunction with full-wave electromagnetic (EM) field simulations. This contribution will show the verification of the improved HOM damping performance by measurements on a single section with 11 cells and on the future 33-cell structures. The parasitic impact of the damping scheme on the travelling wave fundamental passband (FPB) will also be presented.
DOI •	reference for this paper ※ https://doi.org/10.18429/JACoW-IPAC2019-MOPGW076
About •	paper received ※ 11 May 2019 paper accepted ※ 20 May 2019 issue date ※ 21 June 2019
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MOPGW078	Change of Beam Distribution Due to Decoherence in the Presence of Transverse Feedback	feedback, octupole, damping, emittance	281
	S.V. Furuseth, X. Buffat CERN, Geneva, Switzerland S.V. Furuseth EPFL, Lausanne, Switzerland
	The effect of Landau damping is often calculated based on a Gaussian beam distribution in all degrees of freedom. The stability of the beam is however strongly dependent on the details of the distribution. The present study focuses on the change of bunch distributions caused by the decoherence of the excitation driven by an external source of noise, in the presence of both amplitude detuning and a transverse feedback. Both multiparticle tracking simulations and theoretical models show a similar change of the distribution. The possible loss of Landau damping driven by this change is discussed.
DOI •	reference for this paper ※ https://doi.org/10.18429/JACoW-IPAC2019-MOPGW078
About •	paper received ※ 08 April 2019 paper accepted ※ 19 May 2019 issue date ※ 21 June 2019
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MOPGW082	Mitigation of Stray Magnetic Field Effects in CLIC with Passive Shielding	shielding, feedback, collider, hadron	293
	C. Gohil, N. Blaskovic Kraljevic, D. Schulte CERN, Meyrin, Switzerland P. Burrows JAI, Oxford, United Kingdom
	Simulations have shown the Compact Linear Collider (CLIC) is sensitive to external dynamic magnetic fields (stray fields) to the nT level. Due to these extremely tight tolerances, mitigation techniques will be required to prevent performance loss. A passive shielding technique is envisaged as a potential solution. A model for passive shielding is presented along with calculations of its transfer function. Measurements of the transfer function of a promising material (mu-metal) that can be used for passive shielding are presented. The validity of passive shielding models in small amplitude magnetic fields is also discussed.
DOI •	reference for this paper ※ https://doi.org/10.18429/JACoW-IPAC2019-MOPGW082
About •	paper received ※ 01 May 2019 paper accepted ※ 20 May 2019 issue date ※ 21 June 2019
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MOPGW085	Intensity Dependent Effects in the ILC BDS	wakefield, luminosity, collider, linear-collider	305
	P. Korysko, A. Latina CERN, Geneva, Switzerland P. Burrows Oxford University, Physics Department, Oxford, Oxon, United Kingdom
	The International Linear Collider (ILC) is an electron-positron collider being considered for the post-LHC era. Its Beam Delivery System (BDS) receives the beam from the main linac. This beam is then focused to the nanometer scale after going through collimators, beam diagnostic systems, strong magnets, etc. Effects such as wakefields due to resistive-wall, BPMs and collimators make the system very sensitive to the beam intensity. Understanding these effects is crucial in order to demonstrate that the nominal beam size at the Interaction Point (IP) can be reached in realistic scenarios. In this paper, results of the intensity dependence effects in the ILC BDS, simulated with PLACET, are presented.
DOI •	reference for this paper ※ https://doi.org/10.18429/JACoW-IPAC2019-MOPGW085
About •	paper received ※ 23 April 2019 paper accepted ※ 20 May 2019 issue date ※ 21 June 2019
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MOPGW086	Intensity Dependent Effects at ATF2, KEK	collider, linear-collider, wakefield, electron	308
	P. Korysko, A. Latina CERN, Geneva, Switzerland P. Burrows Oxford University, Physics Department, Oxford, Oxon, United Kingdom A. Faus-Golfe LAL, Orsay, France K. Kubo, T. Okugi KEK, Ibaraki, Japan
	The Accelerator Test Facility 2 (ATF2) at KEK is a prototype for the Final Focus Systems of the future e⁺e⁻ linear colliders, the International Linear Collider (ILC) and the Compact Linear Collider (CLIC). In this paper both simulation and experimental results are presented with special emphasis on intensity-dependent effects. The importance of these effects is shown using the PLACET code and realistic ATF2 machine simulations (including beam jitter, misalignment, wakefield, Beam Based Alignment (BBA) correction, …). The latest experimental results are also presented, in particular the impact of the beam intensity on the beam size at the IP.
DOI •	reference for this paper ※ https://doi.org/10.18429/JACoW-IPAC2019-MOPGW086
About •	paper received ※ 23 April 2019 paper accepted ※ 20 May 2019 issue date ※ 21 June 2019
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MOPGW087	GALACTIC and GALACLIC: Two Vlasov Solvers for the Transverse and Longitudinal Planes	impedance, synchrotron, resonance, coupling	312
	E. Métral CERN, Geneva, Switzerland
	GALACTIC and GALACLIC, two Vlasov solvers for the study, in the transverse and longitudinal plane respectively, of single-bunch coherent oscillation modes, were recently developed starting from the Vlasov equation and using a decomposition on the low-intensity eigenvectors, as proposed by Laclare and Garnier. The first Vlasov solver was used for instance to shed light on the destabilising effect of resistive transverse dampers and the second helped understanding the details of the mode-coupling behind some longitudinal microwave instabilities. Both theories are reviewed in detail, highlighting in particular the similarities and peculiarities of the two approaches.
DOI •	reference for this paper ※ https://doi.org/10.18429/JACoW-IPAC2019-MOPGW087
About •	paper received ※ 23 April 2019 paper accepted ※ 20 May 2019 issue date ※ 21 June 2019
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MOPGW088	A Two-Mode Model to Study the Effect of Space Charge on TMCI in the "Long-Bunch" Regime	coupling, space-charge, impedance, optics	316
	E. Métral CERN, Geneva, Switzerland
	Using a two-mode approach for the Transverse Mode-Coupling Instability (TMCI) in the ’short-bunch’ regime (where the mode-coupling takes place between the modes 0 and -1, such as in the CERN LHC), both a reactive damper (ReaD) and Space Charge (SC) are expected to be beneficial: the ReaD would shift the mode 0 up while SC would shift the mode -1 down, but in both cases the coupling (and related instability) would occur at higher intensities. However, the situation is more involved in the ’long-bunch’ regime (where the mode-coupling takes place between higher-order modes, such as in the CERN SPS). As the ReaD modifies only the (main) mode 0 and not the others, it is expected to have no effect for the main mode-coupling. As concerns SC, it modifies all the modes except the mode 0, and the result has been a subject of discussion for two decades. A two-mode approach is discussed in detail in this contribution for the case of a single bunch interacting with a broad-band resonator impedance in the ’long-bunch’ regime. This model reveals in particular that in the presence of space charge, the intensity threshold can only be similar to or lower than that in the absence of space charge.
DOI •	reference for this paper ※ https://doi.org/10.18429/JACoW-IPAC2019-MOPGW088
About •	paper received ※ 23 April 2019 paper accepted ※ 23 May 2019 issue date ※ 21 June 2019
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MOPGW089	Longitudinal Mode-Coupling Instability: GALACLIC Vlasov Solver vs. Macroparticle Tracking Simulations	impedance, coupling, synchrotron, proton	320
	E. Métral CERN, Geneva, Switzerland M. Migliorati Rome University La Sapienza, Roma, Italy M. Migliorati INFN-Roma1, Rome, Italy
	Following the same approach as for the recently developed GALACTIC Vlasov solver in the transverse plane and taking into account the potential-well distortion, a new Vlasov solver, called GALACLIC, was developed for the longitudinal plane. In parallel, a new mode analysis was implemented for the post-processing of the results obtained through macroparticle tracking simulations. The results of the several benchmarks performed between the two methods are presented.
DOI •	reference for this paper ※ https://doi.org/10.18429/JACoW-IPAC2019-MOPGW089
About •	paper received ※ 23 April 2019 paper accepted ※ 23 May 2019 issue date ※ 21 June 2019
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MOPGW095	Beam Dynamics Simulations with Crab Cavities in the SPS Machine	multipole, cavity, luminosity, optics	342
	A. Alekou, A. Alekou, H. Bartosik, H. Bartosik, M. Carlà, Y. Papaphilippou, Y. Papaphilippou, Y. Papaphilippou CERN, Meyrin, Switzerland A. Alekou, A. Alekou, R.B. Appleby, R.B. Appleby UMAN, Manchester, United Kingdom R.B. Appleby Cockcroft Institute, Warrington, Cheshire, United Kingdom
	The LHC Upgrade, called High Luminosity LHC, aims to increase the integrated luminosity by a factor of 10. To achieve this, the project relies on a number of key innovative technologies, including the use of superconducting Crab Cavities with ultra-precise phase control for beam rotation. A set of prototype Crab Cavities has been recently installed in the second largest machine of CERN, the Super Proton Synchrotron (SPS), that operated as a test-bed from May to November of 2018. The tight LHC constraints call for axially non-symmetric cavity designs that introduce high order multipole components. Furthermore, the Crab Cavities in the presence of SPS non-linearities can affect the long term stability of the beam. This paper presents how the SPS dynamic aperture is affected for different cavity, machine and beam configurations.
DOI •	reference for this paper ※ https://doi.org/10.18429/JACoW-IPAC2019-MOPGW095
About •	paper received ※ 06 May 2019 paper accepted ※ 20 May 2019 issue date ※ 21 June 2019
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MOPGW098	Iterative Trajectory-Correction Scheme for the Early Commissioning of Diffraction-Limited Light Sources	MMI, lattice, feedback, storage-ring	353
	Ph. Amstutz, T. Hellert LBNL, Berkeley, USA
	The commissioning of diffraction-limited light sources will be significantly affected by the fact that typical lattice designs rely on very strong focussing elements in order to achieve the small emittance goals. Especially in the early-commissioning phase this can render procedures successfully used in the commissioning of existing third-generation light sources ill-suited for the application to these new machines. In this contribution we discuss an iterative approach to the early trajectory correction, based on the well-known pseudo-inversion of a trajectory-response matrix. Measuring this matrix during early commissioning can be cumbersome, so that an algorithm working with the model response matrix of the lattice is desirable. We discuss the stability of the iteration in the presence of lattice errors, resulting in differences between the actual and the model response matrix. Further, Tikhonov regularization is investigated as a means to trade off the RMS trajectory variation against the strength of the required corrector kicks.
DOI •	reference for this paper ※ https://doi.org/10.18429/JACoW-IPAC2019-MOPGW098
About •	paper received ※ 14 May 2019 paper accepted ※ 23 May 2019 issue date ※ 21 June 2019
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MOPGW099	Vlasov-Fokker-Planck Simulations of Passive Higher-Harmonic Cavity Effects in ALS-U	cavity, impedance, synchrotron, resonance	357
	G. Bassi BNL, Upton, Long Island, New York, USA
	Funding: Work supported by DOE under contract DE-SC0012704 We discuss numerical simulations of the Vlasov-Fokker-Planck equation to model passive higher-harmonic cavity (HHC) effects with parameters of the Advanced Light Source Upgrade (ALS-U. The numerical results, obtained with the SPACE code, are compared with a modal analysis of the coupled-bunch instability theory.
DOI •	reference for this paper ※ https://doi.org/10.18429/JACoW-IPAC2019-MOPGW099
About •	paper received ※ 18 May 2019 paper accepted ※ 24 May 2019 issue date ※ 21 June 2019
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MOPGW104	Equilibria and Synchrotron Stability in Two Energy Storage Rings	electron, storage-ring, damping, focusing	364
	B. Dhital, J.R. Delayen, G.A. Krafft ODU, Norfolk, Virginia, USA J.R. Delayen, Y.S. Derbenev, D. Douglas, G.A. Krafft, F. Lin, V.S. Morozov, Y. Zhang JLab, Newport News, Virginia, USA
	In a dual energy storage ring, the electron beam passes through two loops at markedly different energies E_L, and E_H, i.e., energies for low energy loop and high energy loop respectively. These loops use a common beamline where a superconducting linac at first accelerates the beam from EL to EH and then decelerates the beam from EH to EL in the next pass. There are two basic solutions to the equilibrium problems possible, i.e., ’Storage Ring’ (SR) equilibrium and ’Energy Recovery Linac’ (ERL) equilibrium. SR equilibrium mode more resembles the usual single loop storage ring with strong synchrotron motion and ERL equilibrium mode is the case where RF in two beam passes nearly cancels. Calculations based on linear transfer matrix formalism show that longitudinal stability exists for both SR mode and ERL mode in two energy storage rings.
DOI •	reference for this paper ※ https://doi.org/10.18429/JACoW-IPAC2019-MOPGW104
About •	paper received ※ 14 May 2019 paper accepted ※ 18 May 2019 issue date ※ 21 June 2019
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MOPGW122	Beam-based Measurement of Broadband Longitudinal Impedance at NSLS-II	impedance, vacuum, diagnostics, storage-ring	400
	V.V. Smaluk, B. Bacha, G. Bassi, A. Blednykh BNL, Upton, Long Island, New York, USA
	Funding: Department of Energy Contract No. DE-SC0012704 Interaction of a particle beam with the vacuum chamber impedance is one of the main effects limiting the beam intensity in accelerators. Minimization of the impedance is an essential part of the vacuum chamber design for any new accelerator project. The impedance can be estimated experimentally by measuring beam dynamics effects caused by the beam-impedance interaction. Experience obtained at many accelerator facilities shows the beam-based measurements are often different from the pre-computed impedance budgets, the discrepancy of a factor of two or even more is not unusual. The measurements of broadband longitudinal impedance carried out at NSLS-II are discussed in comparison with the numerically simulated impedance budget.
DOI •	reference for this paper ※ https://doi.org/10.18429/JACoW-IPAC2019-MOPGW122
About •	paper received ※ 15 May 2019 paper accepted ※ 23 May 2019 issue date ※ 21 June 2019
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MOPGW124	Coherent Synchrotron Radiation Simulation for CBETA	linac, lattice, radiation, shielding	406
	W. Lou, C.M. Gulliford, G.H. Hoffstaetter, D. Sagan Cornell University (CLASSE), Cornell Laboratory for Accelerator-Based Sciences and Education, Ithaca, New York, USA C.E. Mayes SLAC, Menlo Park, California, USA N. Tsoupas BNL, Upton, Long Island, New York, USA
	CBETA is an energy recovery linac accelerating from 6 MeV to 150 MeV in four linac passes, using a single return beamline accepting all energies from 42 to 150 MeV. While CBETA gives promise to deliver unprecedentedly high beam current with simultaneously small emittance, Coherent Synchrotron Radiation (CSR) can pose detrimental effect on the beam at high bunch charges and short bunch lengths. To investigate the CSR effects on CBETA, we used the established simulation code Bmad to track a bunch with different parameters. We found that CSR causes phase space dilution, and the effect becomes more significant as the bunch charge and recirculation pass increase. Potential ways to mitigate the effect involving vacuum chamber shielding and increasing bunch length are being investigated.
DOI •	reference for this paper ※ https://doi.org/10.18429/JACoW-IPAC2019-MOPGW124
About •	paper received ※ 15 May 2019 paper accepted ※ 20 May 2019 issue date ※ 21 June 2019
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MOPGW128	Simulation and Analysis of Wake Fields and Trapped RF Modes in Insertion Device Vacuum Chambers at the Canadian Light Source	vacuum, undulator, insertion-device, insertion	414
	E.J. Ericson, D. Bertwistle, M.J. Boland CLS, Saskatoon, Saskatchewan, Canada M.J. Boland, M. Castillo Sosa University of Saskatchewan, Saskatoon, Canada D. Pelz RFS, Kilsyth, Australia
	Funding: CFI, NSERC, NRC, CIHR, the Province of Saskatchewan, WD, WESTGRID, Compute Canada, and the University of Saskatchewan The Canadian Light Source (CLS) synchrotron operates with four in-vacuum insertion devices, three in-vacuum undulators, and one in-vacuum wiggler. Presently, each of the devices occupies half of a straight section. The wiggler is unique in our ring as it is both in-vacuum and shares a straight section with an in-vacuum undulator. We have observed gap dependent beam instabilities in the undulator located in the straight section. In order to better understand the problem, the cause of the instabilities was investigated using 3D electromagnetic modelling. First, the ’trapped’ RF modes (natural resonances) for this undulator chamber, their Q value, and their peak frequencies were analysed using Eigenmode simulation. Secondly, beam excitation of the Eigenmodes was simulated with the Wakefield solver. Herein we present the results of this electromagnetic modelling.
DOI •	reference for this paper ※ https://doi.org/10.18429/JACoW-IPAC2019-MOPGW128
About •	paper received ※ 14 May 2019 paper accepted ※ 23 May 2019 issue date ※ 21 June 2019
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MOPMP008	Electron Driven Positron Source for International Linear Collider	positron, beam-loading, linac, cavity	439
	M. Kuriki, T. Okugi, T. Omori, M. Satoh, Y. Seimiya, J. Urakawa, K. Yokoya KEK, Ibaraki, Japan H. Nagoshi HU/AdSM, Higashi-Hiroshima, Japan K. Negishi Iwate University, Morioka, Iwate, Japan Y. Sumitomo LEBRA, Funabashi, Japan T. Takahashi Hiroshima University, Graduate School of Science, Higashi-Hiroshima, Japan
	Funding: This work is partly supported by Japan-US Cooperative grant for scientific studies, Grant aid for scientific study by MEXT Japan (KAKENHI) To linear colliders, huge amount of positron has to be provided comparing to ring colliders, because the beam is dumped after the collision. Electron Driven ILC Positron source has been designed as a technical backup of the undulator position source including the beam loading effect, etc. The design of the detail will be presented. To linear colliders, huge amount of positron has to be provided comparing to ring colliders, because the beam is dumped after the collision. Electron Driven ILC Positron source has been designed as a technical backup of the undulator position source including the beam loading effect, etc. The design of the detail will be presented.
DOI •	reference for this paper ※ https://doi.org/10.18429/JACoW-IPAC2019-MOPMP008
About •	paper received ※ 13 May 2019 paper accepted ※ 20 May 2019 issue date ※ 21 June 2019
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MOPMP009	Effect of Initial Parameters on the Super Flat Beam Generation with the Phase-Space Rotation for Linear Colliders	emittance, gun, collider, solenoid	442
	M. Kuriki, R. Tamura HU/AdSM, Higashi-Hiroshima, Japan H. Hayano, X.J. Jin, T. Konomi, Y. Seimiya, N. Yamamoto KEK, Ibaraki, Japan S. Kashiwagi Tohoku University, Research Center for Electron Photon Science, Sendai, Japan P. Piot Northern Illinois University, DeKalb, Illinois, USA J.G. Power ANL, Argonne, Illinois, USA K. Sakaue The University of Tokyo, The School of Engineering, Tokyo, Japan M. Washio RISE, Tokyo, Japan
	Funding: This work is partly supported by Japan-US Cooperative grant for scientific studies, Grant aid for scientific study by MEXT Japan (KAKENHI) Kiban B. Linear collider is a concept to realize e⁺e⁻ collision beyond the limitation of the ring colliders by the synchrotron radiation. To obtain an enough luminosity, eg. 1.0·10⁺³⁴ cm^-2sec^-1, the beam is focused down to nano-meter size with a high aspect ratio. This super flat beam is useful to improve the luminosity and to compensate the beam-beam effect, eg. Beamstrahlung. In a conventional design, the super-flat beam is produced by radiation damping in a storage ring. We propose to produce this super-flat beam with phase-space rotation techniques. We employ both Round to Flat Beam Transformation and Transverse to Longitudinal Emittance eXchange, the super flat beam can be generated by controlling the space-charge effect which spoiled the performance. We present the RFBT performance with respect to the initial conditions, i.e. beam size, initial emittance, solenoid field (strength and profile), etc.
DOI •	reference for this paper ※ https://doi.org/10.18429/JACoW-IPAC2019-MOPMP009
About •	paper received ※ 13 May 2019 paper accepted ※ 20 May 2019 issue date ※ 21 June 2019
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MOPMP033	LHC Run 2 Optics Commissioning Experience in View of HL-LHC	optics, luminosity, coupling, experiment	508
	R. Tomás, F.S. Carlier, J.M. Coello de Portugal, J. Dilly, S.D. Fartoukh, E. Fol, D. Gamba, A. Garcia-Tabares, M. Giovannozzi, M. Hofer, E.H. Maclean, L. Malina, T.H.B. Persson, P.K. Skowroński, M. Solfaroli, M.L. Spitznagel, A. Wegscheider, J. Wenninger, D.W. Wolf CERN, Geneva, Switzerland
	LHC Run 2 has achieved a beta lower than a factor 2 below design. This has significantly challenged optics measurement and correction techniques in the linear and non-linear regimes, leading to the development of new approaches. Furthermore, experimenting with a large variety of optics has allowed facing the difficulties of future optics and gaining understanding of the machine imperfections. A summary of these aspects is given in view of their implications for the HL-LHC Project.
DOI •	reference for this paper ※ https://doi.org/10.18429/JACoW-IPAC2019-MOPMP033
About •	paper received ※ 07 May 2019 paper accepted ※ 20 May 2019 issue date ※ 21 June 2019
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MOPMP038	Investigation of CLIC 380 GeV Post-Collision Line	site, dipole, collider, linear-collider	528
	R.M. Bodenstein, A. Abramov, S.T. Boogert, P. Burrows, L.J. Nevay JAI, Oxford, United Kingdom D. Schulte, R. Tomás CERN, Meyrin, Switzerland
	It has been proposed that the Compact Linear Collider (CLIC) be commissioned in stages, starting with a lower-energy, 380 GeV version for the first stage, and concluding with a 3 TeV version for the final stage. In the Conceptual Design Report (CDR) published in 2012, the post-collision line is described for the 3 TeV and 500 GeV stages. However, the post-collision line for the 380 GeV design was not investigated. This work will describe the simulation studies performed in BDSIM for the 380 GeV post-collision line.
DOI •	reference for this paper ※ https://doi.org/10.18429/JACoW-IPAC2019-MOPMP038
About •	paper received ※ 13 May 2019 paper accepted ※ 18 May 2019 issue date ※ 21 June 2019
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MOPMP052	Numerical Simulations of the DC Wire Prototypes in LHC for Enhancing the HL-LHC Performances	experiment, luminosity, optics, resonance	566
	A. Poyet Université Grenoble Alpes, Grenoble, France S.D. Fartoukh, N. Karastathis, Y. Papaphilippou, K. Skoufaris, G. Sterbini CERN, Geneva, Switzerland
	For the last 15 years, the compensation of the Beam-Beam Long-Range (BBLR) interaction in colliders using DC wires has been studied. In 2015, in the frame of the HL-LHC project, it has been shown that a compensation of all the Resonance Driving Terms (RDTs) generated by the BBLR interaction is possible using wires with constraints on their transverse and longitudinal positions. In 2017, an experimental campaign has been launched in the present LHC, with wires installed in sub-optimal positions due to integration constraints. The aim of this paper is therefore to apply the formalism developped for HL-LHC to the LHC case and to compare the experimental results to the numerical tracking studies of the compensation using wires.
DOI •	reference for this paper ※ https://doi.org/10.18429/JACoW-IPAC2019-MOPMP052
About •	paper received ※ 06 May 2019 paper accepted ※ 20 May 2019 issue date ※ 21 June 2019
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MOPMP053	Numerical Optimization of DC Wire Compensation in HL-LHC	operation, collider, luminosity, hadron	570
	K. Skoufaris, S.D. Fartoukh, N. Karastathis, Y. Papaphilippou, D. Pellegrini, A. Poyet, A. Rossi, G. Sterbini CERN, Meyrin, Switzerland
	The electromagnetic field generated from a set of DC wires parallel to the beam opens the path to the compensation of the beam-beam long-range (BBLR) interactions for the future operation of large hadron colliders, in particular for the upcoming High Luminosity upgrade of the Large Hadron Collider (HL-LHC). The effectiveness and simplicity of a current carrying wire are critical for overcoming some technical constraints of the machine. In order to better understand the potential of this device for the HL-LHC, various simulation studies are presented. The different observables are the dynamic aperture and the frequency analysis.
DOI •	reference for this paper ※ https://doi.org/10.18429/JACoW-IPAC2019-MOPMP053
About •	paper received ※ 03 May 2019 paper accepted ※ 20 May 2019 issue date ※ 21 June 2019
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MOPRB011	Progress on Muon Ionization Cooling Demonstration with MICE	emittance, experiment, detector, framework	594
	C. Hunt Imperial College of Science and Technology, Department of Physics, London, United Kingdom V.C. Palladino INFN-Napoli, Napoli, Italy C.G. Whyte USTRAT/SUPA, Glasgow, United Kingdom
	Funding: STFC, NSF, DOE, INFN, CHIPP andd more The Muon Ionization Cooling Experiment (MICE) at RAL has collected extensive data to study the ionization cooling of muons. Several million individual particle tracks have been recorded passing through a series of focusing magnets in a number of different configurations and a liquid hydrogen or lithium hydride absorber. Measurement of the tracks upstream and downstream of the absorber has shown the expected effects of the 4D emittance reduction. Further studies are providing now more and deeper insight. Submitted by the chair of our MICE speakers bureau. If accepted, a member of the collaboration will soon be identified to present the contribution and will register immediately after.
DOI •	reference for this paper ※ https://doi.org/10.18429/JACoW-IPAC2019-MOPRB011
About •	paper received ※ 15 May 2019 paper accepted ※ 23 May 2019 issue date ※ 21 June 2019
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MOPRB033	Preliminary Research of HOM for 100MHz Superconducting Cavity in the Pre-Research Project of HALS	HOM, cavity, impedance, damping	649
	Y.G. Tang, L. Wang, C.-F. Wu USTC/NSRL, Hefei, Anhui, People’s Republic of China
	A 100MHz QWR superconducting cavity is researched in the pre-research project of Hefei Advanced Light Source (HALS). Higher order modes (HOM) damping is a big challenge for synchrotron radiation light source. In this paper, we first apply the novel choke mode structure to the 100MHz QWR (quarter wave resonator) cavity in order to damp the HOM. We identify the main harmful higher order modes. The HOMs in the QWR cavity are suppressed by optimizing the choke dimensions. The broadband HOM impedance spectrum of the cavity was also evaluated by calculating the beam induced wake potential in time domain. The results show that choke mode structure has a good HOM damping effect on the QWR cavity.
DOI •	reference for this paper ※ https://doi.org/10.18429/JACoW-IPAC2019-MOPRB033
About •	paper received ※ 25 April 2019 paper accepted ※ 20 May 2019 issue date ※ 21 June 2019
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MOPRB046	Status of the ESSnuSB Accumulator Design	linac, space-charge, injection, target	666
	Y. Zou, T.J.C. Ekelöf, M. Olvegård, R.J.M.Y. Ruber Uppsala University, Uppsala, Sweden E. Bouquerel, M. Dracos IPHC, Strasbourg Cedex 2, France M. Eshraqi, B. Gålnander ESS, Lund, Sweden H.O. Schönauer, E.H.M. Wildner CERN, Geneva, Switzerland
	Funding: This project is supported by the COST Action CA15139 EuroNuNet. It has received funding from the European Union’s Horizon 2020 research and innovation programme under grant agreement No 777419. The 2.0 GeV, 5 MW proton linac for the European Spallation Source, ESS, will have the capacity to accelerate additional pulses and send them to a neutrino target, providing an excellent opportunity to produce an unprecedented high performance neutrino beam, the ESS neutrino Super Beam, ESSnuSB, to measure, with precision, the CP violating phase at the 2nd oscillation maximum. In order to comply with the acceptance of the target and horn systems that will form the neutrino super beam, the long pulses from the linac must be compressed by about three orders of magnitude with minimal particle loss, something that will be achieved through multi-turn charge-exchange injection in an accumulator ring. This ring will accommodate over 2·10¹⁴ protons, which means that several design challenges are encountered. Strong space charge forces, low-loss injection with phase space painting, efficient collimation, a reliable charge stripping system, and e-p instabilities are some of the important aspects central to the design work. This paper presents the status of the accumulator ring design, with multi-particle simulations of the injections procedure.
DOI •	reference for this paper ※ https://doi.org/10.18429/JACoW-IPAC2019-MOPRB046
About •	paper received ※ 14 May 2019 paper accepted ※ 20 May 2019 issue date ※ 21 June 2019
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MOPRB048	Collimation System Studies for the FCC-hh	collimation, proton, collider, hadron	669
	R. Bruce, A. Abramov, A. Bertarelli, M.I. Besana, F. Carra, F. Cerutti, M. Fiascaris, G. Gobbi, A.M. Krainer, A. Lechner, A. Mereghetti, D. Mirarchi, J. Molson, M. Pasquali, S. Redaelli, D. Schulte, E. Skordis, M. Varasteh Anvar CERN, Geneva, Switzerland A. Abramov JAI, Egham, Surrey, United Kingdom A. Faus-Golfe LAL, Orsay, France M. Serluca IN2P3-LAPP, Annecy-le-Vieux, France
	The Future Circular Collider (FCC-hh) is being designed as a 100 km ring that should collide 50 TeV proton beams. At 8.3 GJ, its stored beam energy will be a factor 28 higher than what has been achieved in the Large Hadron Collider, which has the highest stored beam energy among the colliders built so far. This puts unprecedented demands on the control of beam losses and collimation, since even a tiny beam loss risks quenching superconducting magnets. We present in this article the design of the FCC-hh collimation system and study the beam cleaning through simulations of tracking, energy deposition, and thermo-mechanical response. We investigate the collimation performance for design beam loss scenarios and potential bottlenecks are highlighted.
DOI •	reference for this paper ※ https://doi.org/10.18429/JACoW-IPAC2019-MOPRB048
About •	paper received ※ 18 April 2019 paper accepted ※ 20 May 2019 issue date ※ 21 June 2019
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MOPRB049	Study of Beam-Gas Interactions at the LHC for the Physics Beyond Colliders Fixed-Target Study	target, proton, collider, experiment	673
	C. Boscolo Meneguolo, R. Bruce, F. Cerutti, M. Ferro-Luzzi, M. Giovannozzi, A. Mereghetti, J. Molson, S. Redaelli CERN, Geneva, Switzerland A. Abramov JAI, Egham, Surrey, United Kingdom
	Among several working groups formed in the framework of Physics Beyond Colliders study, launched at CERN in September 2016, there is one investigating specific fixed-target experiment proposals. Of particular interest is the study of high-density unpolarized or polarized gas target to be installed in the LHCb detector, using storage cells to enhance the target density. This work studies the impact of the interactions of 7 TeV proton beams with such gas targets on the LHC machine in terms of particle losses.
DOI •	reference for this paper ※ https://doi.org/10.18429/JACoW-IPAC2019-MOPRB049
About •	paper received ※ 17 April 2019 paper accepted ※ 19 May 2019 issue date ※ 21 June 2019
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MOPRB050	Performance of the Collimation System During the 2018 Lead Ion Run at the Large Hadron Collider	collimation, heavy-ion, proton, hadron	677
	N. Fuster-Martínez, R. Bruce, J.M. Jowett, A. Mereghetti, D. Mirarchi, S. Redaelli CERN, Meyrin, Switzerland
	As part of the Large Hadron Collider (LHC) heavy-ion research programme, the last month of the 2018 LHC run was dedicated to Pb ion physics. Several heavy-ion runs have been performed since the start-up of the LHC. These runs are challenging for collimation, despite lower intensities, because of the degraded cleaning observed compared to protons. This is due to the differences of the interaction mechanisms in the collimators. Ions experience fragmentation and electromagnetic dissociation that result in a substantial flux of off-rigidity particles that escape the collimation system. In this paper, the collimation system performance and the experience gained during the 2018 Pb ion run are presented. The measured performance is compared with the expectation from the Sixtrack-FLUKA coupling simulations and the agreement discussed.
DOI •	reference for this paper ※ https://doi.org/10.18429/JACoW-IPAC2019-MOPRB050
About •	paper received ※ 07 May 2019 paper accepted ※ 19 May 2019 issue date ※ 21 June 2019
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MOPRB057	An Approach to Alleviating Heavy Beam Loading Effect on the Synchrotron Machine Through the Existed Low Level RF Feedback System	cavity, feedback, beam-loading, impedance	697
	L.-H. Chang, F.Y. Chang, M.H. Chang, S.W. Chang, L.J. Chen, F.-T. Chung, Y.T. Li, M.-C. Lin, Z.K. Liu, C.H. Lo, Ch. Wang, M.-S. Yeh, T.-C. Yu NSRRC, Hsinchu, Taiwan
	To pursue the highest brightness and intensity of the synchrotron light, the synchrotron machines are pushed to operate with as high as possible of the beam current. To suppress the heavy beam loading effects, the direct RF feedback is currently widely used. This paper provides an another approach to alleviating the heavy beam loading effects on machine operation. Different from the direct RF feedback technique, this approach need not add additional feedback loop to the existed RF feedback system. Applying a proper angle rotation to the I-Q error signals of the cavity voltage, before entering the existed feedback loop, is the only action required in this approach. The paper will explain the working mechanism and investigate the behaviour of this approach, through an example case, with numerical simulation.
DOI •	reference for this paper ※ https://doi.org/10.18429/JACoW-IPAC2019-MOPRB057
About •	paper received ※ 16 April 2019 paper accepted ※ 18 May 2019 issue date ※ 21 June 2019
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MOPRB058	Collimation of Partially Stripped Ion Beams in the LHC	collimation, operation, collider, hadron	700
	A. Abramov, L.J. Nevay JAI, Egham, Surrey, United Kingdom R. Bruce, N. Fuster-Martínez, A.A. Gorzawski, M.W. Krasny, J. Molson, S. Redaelli, M. Schaumann CERN, Meyrin, Switzerland
	In the scope of the Physics Beyond Colliders studies, the Gamma Factory initiative proposes the use of partially stripped ions as a driver of a new type, high intensity photon source in CERN’s Large Hadron Collider (LHC). In 2018, the LHC accelerated and stored partially stripped 208-Pb-81+ ions for the first time. The collimation system efficiency recorded during this test was found to be prohibitively low. The worst losses were localised in the dispersion suppressor (DS) of the betatron-cleaning insertion. Analytic arguments and simulations show that the large losses are driven by the stripping of the remaining electron from the Pb nucleus by the primary collimators. The rising dispersion in the DS pushes the resulting off-rigidity, fully-stripped ions into the aperture of the superconducting magnets. In this study the measured loss maps are compared against results from simulations. Different mitigation strategies are outlined, including a dispersion suppressor (DS) collimator, crystal collimation or an orbit bump.
DOI •	reference for this paper ※ https://doi.org/10.18429/JACoW-IPAC2019-MOPRB058
About •	paper received ※ 10 May 2019 paper accepted ※ 20 May 2019 issue date ※ 21 June 2019
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MOPRB059	Collimation of Heavy-Ion Beams in the HE-LHC	collimation, collider, proton, hadron	704
	A. Abramov, L.J. Nevay JAI, Egham, Surrey, United Kingdom R. Bruce, M.P. Crouch, N. Fuster-Martínez, A. Mereghetti, J. Molson, S. Redaelli CERN, Meyrin, Switzerland
	A design study for a future collider to be built in the LHC tunnel, the High-Energy Large Hadron Collider (HE-LHC), has been launched as part of the Future Circular Collider (FCC) study at CERN. It would provide proton collisions at a centre-of-mass energy of 27 TeV as well as collisions of heavy ions at the equivalent magnetic rigidity. HE-LHC is being designed under the stringent constraint of using the existing tunnel and therefore the resulting lattice and optics differ in layout and phase advance from the LHC. It is necessary to evaluate the performance of the collimation system for ion beams in HE-LHC in addition to proton beams. In the case of ion beams, the fragmentation and electromagnetic dissociation that relativistic heavy ions can undergo in collimators, as well as the unprecedented energy per nucleon of the HE-LHC, requires dedicated simulations. Results from a study of collimation efficiency for the nominal lead ion (Pb-82-208) beams performed with the SixTrack-FLUKA coupling framework are presented. These include loss maps with comparison against an estimated quench limit as well as detailed considerations of loss spikes in the superconducting aperture for critical sections of the machine such as the dispersion suppressors.
DOI •	reference for this paper ※ https://doi.org/10.18429/JACoW-IPAC2019-MOPRB059
About •	paper received ※ 18 April 2019 paper accepted ※ 23 May 2019 issue date ※ 21 June 2019
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MOPRB060	Simulating Novel Collimation Schemes for High-Luminosity LHC With Merlin++	proton, scattering, collimation, electron	708
	S.C. Tygier, R.B. Appleby UMAN, Manchester, United Kingdom R.J. Barlow, S. Rowan IIAA, Huddersfield, United Kingdom
	Due to the large stored beam energy in the HL-LHC new collimation technologies must be used to protect the machine. Active halo control of the proton beam halo with a Hollow Electron Lens can give a kick to protons at the edge of the beam without effecting the core. Various modes of operation are possible for example the electron lens can have a continuous current or it can be pulsed to different amplitudes for each passage of the proton beam. In this article we use Merlin++ simulations to show the performance of these modes for HL-LHC parameters. We also present recent simulations comparing scattering models in Merlin++.
DOI •	reference for this paper ※ https://doi.org/10.18429/JACoW-IPAC2019-MOPRB060
About •	paper received ※ 08 May 2019 paper accepted ※ 20 May 2019 issue date ※ 21 June 2019
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MOPRB061	Simulations and Measurements of Coherent Synchrotron Radiation at the MAX-IV Short Pulse Facility	radiation, detector, electron, dipole	712
	B.S. Kyle University of Manchester, Manchester, United Kingdom R.B. Appleby UMAN, Manchester, United Kingdom M. Brandin, E. Mansten, S. Thorin MAX IV Laboratory, Lund University, Lund, Sweden T.H. Pacey STFC/DL/ASTeC, Daresbury, Warrington, Cheshire, United Kingdom P.H. Williams Cockcroft Institute, Warrington, Cheshire, United Kingdom J. Wolfenden The University of Liverpool, Liverpool, United Kingdom
	The Coherent Synchrotron Radiation (CSR) interaction is a source of unwanted correlated energy spread in short-bunch Free-Electron Lasers (FEL), diluting the desired FEL spectrum and reducing the total brightness of the light source. Many accelerator codes make use of 1-dimensional approximations in the calculation of the CSR-wake, which breaks down for bunch dimensions typical within bunch compressor dipoles in FELs. General Particle Tracer simulations of the CSR interaction make use of the 3-dimensional bunch distribution, making it advantageous in modelling the short-bunch, high aspect ratio regimes typical of modern 4th-generation light sources. Measurements of THz CSR emitted from the final bunch compressor dipole of the SP02 beamline at the MAX-IV Short Pulse Facility (SPF) were used, alongside start-to-end GPT and Elegant simulations, to characterize coherent radiation emission across a broad range of bunch lengths.
DOI •	reference for this paper ※ https://doi.org/10.18429/JACoW-IPAC2019-MOPRB061
About •	paper received ※ 14 May 2019 paper accepted ※ 20 May 2019 issue date ※ 21 June 2019
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MOPRB064	Precision Modelling of Energy Deposition in the LHC using BDSIM	proton, detector, collimation, beam-losses	723
	S.D. Walker, A. Abramov, S.T. Boogert, S.M. Gibson, L.J. Nevay, H. Pikhartova JAI, Egham, Surrey, United Kingdom
	A detailed model of the Large Hadron Collider (LHC) has been built using Beam Delivery Simulation (BDSIM) for studying beam loss patterns and is presented and discussed in this paper. BDSIM is a program which builds a Geant4 accelerator model from generic components bridging accelerator tracking routines and particle physics to seamlessly simulate the traversal of particles and any subsequent energy deposition in particle accelerators. The LHC model described here has been further refined with additional features to improve the accuracy of the model, including specific component geometries, tunnel geometry, and more. BDSIM has been extended so that more meaningful comparisons with other simulations and data can be made. Firstly, BDSIM can now record losses in the same way that SixTrack does: when a primary exceeds the limits of the aperture it is recorded as a loss. Secondly, by placing beam loss monitors (BLMs) within the BDSIM model and recording the simulated dose and energy deposition, it can be directly compared with real BLM data. These results are presented here and compared with SixTrack and BLM data from a typical fill in 2018.
DOI •	reference for this paper ※ https://doi.org/10.18429/JACoW-IPAC2019-MOPRB064
About •	paper received ※ 15 May 2019 paper accepted ※ 20 May 2019 issue date ※ 21 June 2019
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MOPRB069	Generation of High Power Short Rf Pulses using an X-Band Metallic Power Extractor Driven by High Charge Multi-Bunch Train	pick-up, experiment, multipactoring, acceleration	734
	J.H. Shao, M.E. Conde, D.S. Doran, G. Ha, W. Liu, J.G. Power, C. Whiteford, E.E. Wisniewski ANL, Argonne, Illinois, USA H.B. Chen, M.M. Peng, J. Shi, H. Zha TUB, Beijing, People’s Republic of China C.-J. Jing Euclid TechLabs, LLC, Solon, Ohio, USA J. Seok UNIST, Ulsan, Republic of Korea
	Short pulse two-beam acceleration (TBA) is a structure wakefield acceleration (SWFA) approach aiming to achieve gradient above 250 MV/m using rf pulses less than 20 ns. An X-band 11.7 GHz metallic power extractor has been developed as the power source to test accelerating structures in this extreme regime. The power extractor is designed to be driven by high charge bunches separated by 769.2 ps (9 times the X-band period) on an L-band 1.3 GHz beamline. In the recent experiment, ~280 MW rf pulses with 3 ns flat-top have been measured by a coaxial rf pickup when driven by 8-bunch trains with a total charge of ~500 nC. The power level is ~50% lower than the theoretical prediction and simulation. Experimental investigation suggests that the missing power was mainly caused by the multipacting issue inside the rf pickup, which could be eliminated by a newly-designed directional coupler.
DOI •	reference for this paper ※ https://doi.org/10.18429/JACoW-IPAC2019-MOPRB069
About •	paper received ※ 19 May 2019 paper accepted ※ 20 May 2019 issue date ※ 21 June 2019
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MOPRB081	Electron Beam’s Closed Orbit in the Crab Crossing Scheme of Future Electron-Ion Colliders	electron, closed-orbit, luminosity, cavity	762
	Y. Hao, V. Ptitsyn BNL, Upton, Long Island, New York, USA J. Qiang LBNL, Berkeley, California, USA
	In crab-crossing collision geometry the closed orbit of the electron beam will be altered by the beam-beam interaction and the tilted head and tail of the ion beam. We will present the linear model to determine the closed orbit and compare with the simulation. Also, the relation of the closed orbit and the synchro-betatron resonance will be presented.
DOI •	reference for this paper ※ https://doi.org/10.18429/JACoW-IPAC2019-MOPRB081
About •	paper received ※ 15 May 2019 paper accepted ※ 20 May 2019 issue date ※ 21 June 2019
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MOPRB082	Scaling Properties of the Synchro-Beta Resonance in Crab Crossing Scheme of Future Electron Ion Collider	luminosity, resonance, electron, cavity	766
	Y. Hao, Y. Luo, V. Ptitsyn BNL, Upton, Long Island, New York, USA J. Qiang LBNL, Berkeley, California, USA
	The synchro - beta resonance due to the beam-beam interaction was predicted by the strong-strong simulation in the future electron-ion collider designs. In this paper, we study the scaling properties of the degradation rate of this unwanted resonance. These studies motivated the possible countermeasures of the luminosity degradation associated with the resonance.
DOI •	reference for this paper ※ https://doi.org/10.18429/JACoW-IPAC2019-MOPRB082
About •	paper received ※ 15 May 2019 paper accepted ※ 20 May 2019 issue date ※ 21 June 2019
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MOPRB090	Simulation Challenges for eRHIC Beam-Beam Study	electron, proton, damping, emittance	785
	Y. Luo, F.J. Willeke BNL, Upton, Long Island, New York, USA Y. Hao FRIB, East Lansing, Michigan, USA J. Qiang LBNL, Berkeley, California, USA Y. Roblin, H. Zhang JLab, Newport News, Virginia, USA
	Funding: Work supported by Brookhaven Science Associates, LLC under Contract No. DE-AC02-98CH10886 with the U.S. Department of Energy. The 2015 Nuclear Science Advisory Committee Long Rang Plan identified the need for an electron-ion collider (EIC) facility as a gluon microscope with capabilities beyond those of any existing accelerator complex. To reach the required high energy, high luminosity, and high polarization, the eRHIC design, based on the existing heavy ion and polarized proton collider RHIC, adopts a very small \beta-function at the interaction points, a high collision repetition rate, and a novel hadron cooling scheme. A full crossing angle of 22 mrad and crab cavities for both electron and proton rings are required. In this article, we will present the high priority R\&D items related to the beam-beam interaction studies for the current eRHIC design, the simulation challenges, and our plans and methods to address them. Recent progresses on this project are reported too.
DOI •	reference for this paper ※ https://doi.org/10.18429/JACoW-IPAC2019-MOPRB090
About •	paper received ※ 14 May 2019 paper accepted ※ 20 May 2019 issue date ※ 21 June 2019
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MOPRB091	Combined Strong-Strong and Weak-Strong Beam-Beam Simulations for Crabbed Collision in eRHIC	electron, proton, luminosity, cavity	788
	Y. Luo, G. Bassi, M. Blaskiewicz, W. Fischer, Y. Hao, C. Montag, V. Ptitsyn, V.V. Smaluk, F.J. Willeke BNL, Upton, Long Island, New York, USA K. Ohmi KEK, Ibaraki, Japan J. Qiang LBNL, Berkeley, California, USA
	Funding: Work supported by Brookhaven Science Associates, LLC under Contract No. DE-AC02-98CH10886 with the U.S. Department of Energy. In the eRHIC, to compensate the geometric luminosity loss, local crab cavities on both sides of the interaction points are to adopted. The previous strong-strong beam-beam simulations showed that the luminosity degradation depends on the crab cavity frequency, proton synchrotron tune, proton bunch length and so on. In this article, we apply a combined strong-strong and weak-strong beam-beam simulation to investigate the incoherent and coherent beam motions with crabbed collison, and to calculate more realistic beam emittance growth rates and luminosity degradation rate.
DOI •	reference for this paper ※ https://doi.org/10.18429/JACoW-IPAC2019-MOPRB091
About •	paper received ※ 14 May 2019 paper accepted ※ 20 May 2019 issue date ※ 21 June 2019
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MOPRB092	Symplectic and Exact Tracking of Low Energy 197Au⁷⁸⁺ in the Relativistic Heavy Ion Collider	electron, quadrupole, storage-ring, lattice	791
	Y. Luo, W. Fischer, F. Méot, G. Robert-Demolaize BNL, Upton, Long Island, New York, USA
	Funding: Work supported by Brookhaven Science Associates, LLC under Contract No. DE-AC02-98CH10886 with the U.S. Department of Energy. In the coming RHIC low energy scan, the electron cooling technique is to be used to cool the ions 197Au⁷⁹⁺ with its energy range between 3.85~GeV/nucleon to 5.75~GeV/nucleon. To overlap the electron beam and the 197Au⁷⁹⁺ beam at the cooling section, a recombination monitor is to be used to detect the maximum flux of 197Au⁷⁸⁺ ions generated in the cooling section. In the previous studies, we tracked 197Au⁷⁸⁺ ions through the RHIC lattice defined with 197Au⁷⁹⁺ with an equivalent momentum deviation. In the article, we explode different symplectic ways to track 197Au⁷⁸⁺ ions exactly. We calculate and compare the trajectories and loss map of 197Au⁷⁸⁺ ions through the RHIC ring.
DOI •	reference for this paper ※ https://doi.org/10.18429/JACoW-IPAC2019-MOPRB092
About •	paper received ※ 14 May 2019 paper accepted ※ 20 May 2019 issue date ※ 21 June 2019
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MOPRB104	A Parameter Study for Improving the Performance of the Production Target for the Fermilab Muon g-2 Experiment	target, experiment, storage-ring, proton	806
	D. Stratakis Fermilab, Batavia, Illinois, USA
	The target station of the Muon g-2 Experiment is one of the central pieces for the production of secondary pions which eventually will decay to the desired mu-ons. In this paper, we report adjustments made to opti-mize its performance. For instance, in the simulation we vary the size of the primary incoming beam and examine its impact on the downstream production. We then compare this with the actual measured beam size upstream of the target. In addition, we examine the sensitivity in performance with the strength of the lithium lens for pion capture and the distance between lens and target. We compare measured data with simu-lation results.
DOI •	reference for this paper ※ https://doi.org/10.18429/JACoW-IPAC2019-MOPRB104
About •	paper received ※ 13 May 2019 paper accepted ※ 20 May 2019 issue date ※ 21 June 2019
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MOPRB105	Measurement and Analysis of Beam Phase-space Distributions for the Fermilab Muon Campus accelerator complex	quadrupole, emittance, framework, experiment	810
	A. Ramirez University of Houston, Houston, Texas, USA D. Stratakis Fermilab, Batavia, Illinois, USA
	The Muon g-2 experiment at Fermilab is tasked with measuring the muon’s anomalous magnetic moment with high precision. Since the experiment requires large amounts of muons, it is imperative to systematically study the behavior of the beam along the transport line. Unfortunately, the available diagnostics only provide beam information in X-Y space. For a complete evaluation, information of the phase-space is required. This paper demonstrates a technique to measure the beam phase-space distribution by using a set of beam profiles. First, we establish the theoretical framework that describes the principle of the technique. Next, we apply the technique at four different locations along the accelerator delivery line. Finally, we compare our findings to predictions from tracking simulations. Our results indicate that the beam phase-space volume is conserved, along the beam delivery line, suggesting minimal loses and linear transport as expected by design. Compared to the simulations, there is good agreement in both horizontal and vertical plane with the former being at the 4% level while the latter being in the 15% level. Our proposed technique is expected to provide a promising approach for optimizing injection and thereby improving the performance of the Muon g-2 Experiment.
DOI •	reference for this paper ※ https://doi.org/10.18429/JACoW-IPAC2019-MOPRB105
About •	paper received ※ 13 May 2019 paper accepted ※ 20 May 2019 issue date ※ 21 June 2019
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MOPRB106	3D Theory of Microbunched Electron Cooling for Electron-Ion Colliders	electron, hadron, kicker, betatron	814
	G. Stupakov, P. Baxevanis SLAC, Menlo Park, California, USA
	Funding: This work was supported by the Department of Energy, Contract No. DE-AC02-76SF00515. The Microbunched Electron Cooling (MBEC) * is a promising cooling technique that can find applications in future hadron and electron-ion colliders. A 1D model of MBEC has been recently developed in Ref. *. This model predicts the cooling time below two hours for eRHIC 255 GeV proton beams, when two amplification sections are used in the cooling system. In this work, we go beyond the 1D model of Ref. and develop a realistic 3D theory of MBEC. Our approach is based on the analysis of the dynamics of microscopic 3D fluctuations in the electron and hadron beams during their interaction and propagation through the system. We derive an analytical expression for the cooling rate and optimize it for the parameters of eRHIC. Our analytical results are in reasonable agreement with simulations. * D. Ratner. Phys. Rev. Lett. 111, 084802 (2013). ** G. Stupakov. PRAB 21, 114402 (2018)
DOI •	reference for this paper ※ https://doi.org/10.18429/JACoW-IPAC2019-MOPRB106
About •	paper received ※ 29 April 2019 paper accepted ※ 18 May 2019 issue date ※ 21 June 2019
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MOPRB116	Laser Sculpted Cool Proton Beams	laser, emittance, linac, proton	826
	S.M. Gibson, L.J. Nevay Royal Holloway, University of London, Surrey, United Kingdom S.E. Alden, S.M. Gibson, L.J. Nevay JAI, Egham, Surrey, United Kingdom
	Funding: We acknowledge support by STFC grant ST/P003028/1 Hydrogen ion accelerators, such as CERN’s Linac4, are increasingly used as the front end of high power proton drivers for high energy physics, spallation neutron sources and other applications. Typically, a foil strips the hydrogen ion beam to facilitate charge-exchange injection of protons into orbits of high energy accelerators, in which the resulting emittance is dominated by phase-space painting. In this paper, a new method to laser extract a narrow beam of neutralised hydrogen from the parent H⁻ ion beam is proposed. Subsequent foil stripping and capture of protons into a storage ring generates cool proton bunches with significantly reduced emittance compared to the parent beam. The properties of the extracted proton beam can be precisely controlled and sculpted by adjusting the optical parameters of the laser beam. Recirculation of the parent beam allows time for space-charge effects to repopulate the emittance phase space prior to repeated laser extraction. We present particle tracking simulations of the proposed scheme, including the laser-particle interaction with realistic optical parameters and show the resulting emittance is reduced. Developments for an experimental demonstration of a laser controlled particle beam are outlined. In principle, the proposed scheme could considerably reduce the emittance of protons bunches injected into an accelerator, such as the LHC.
DOI •	reference for this paper ※ https://doi.org/10.18429/JACoW-IPAC2019-MOPRB116
About •	paper received ※ 16 May 2019 paper accepted ※ 23 May 2019 issue date ※ 21 June 2019
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MOPTS010	Simulation of the Guide Field Flipping Procedure for the Frequency Domain Method	GUI, lattice, sextupole, dipole	858
	A.E. Aksentyev FZJ, Jülich, Germany A.E. Aksentyev MEPhI, Moscow, Russia A.E. Aksentyev, V. Senichev RAS/INR, Moscow, Russia
	The spin vector of a particle injected into a perfectly aligned storage ring precesses about the vertically-orientated guide field. In the presence of an Electric Dipole Moment (EDM), the spin precession axis acquires a proportional radial component. However, in an imperfect ring, rotational magnet misalignments induce a radial component to the spin precession axis, related to the Magnetic Dipole Moment (MDM). In the Frequency Domain Method, [] this additional precession is dealt with by consecutively injecting the beam in opposite directions, and constructing the EDM estimator as the sum of the clockwise and counter-clockwise vertical plane precession frequencies. Since the radial MDM component changes sign when the magnetic field direction is reversed, it cancels in the sum, leaving only the EDM effect. In order to reproduce the guide field magnitude with precision sufficient for the cancellation of the MDM effect, we propose to calibrate the guide field via the horizontal plane precession frequency. In the present work we describe the algorithm of the field flipping procedure, and do a numerical simulation. [] Senichev Y, Aksentev A, Ivanov A, Valetov E. Frequency domain method of the search for the deuteron electric dipole moment in a storage ring with imperfections. arXiv:171106512. 2017 Nov 17.
DOI •	reference for this paper ※ https://doi.org/10.18429/JACoW-IPAC2019-MOPTS010
About •	paper received ※ 08 April 2019 paper accepted ※ 23 May 2019 issue date ※ 21 June 2019
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MOPTS012	Spin Decoherence in the Frozen Spin Storage Ring Method of Search for a Particle EDM	sextupole, storage-ring, lattice, betatron	864
	A.E. Aksentyev FZJ, Jülich, Germany A.E. Aksentyev MEPhI, Moscow, Russia A.E. Aksentyev, V. Senichev RAS/INR, Moscow, Russia
	Spin coherence refers to a measure of preservation of polarization in an initially polarized beam. The spin vector of a particle injected into a storage ring starts to precess about the vertical magnetic field vector in accordance with the Thomas-BMT equation. The precession frequency is dependent on the equilibrium-level energy, which differs across the beam particles. This does not pose a problem when the initial polarization is vertical; however, the Frozen Spin Storage Ring EDM search method [] requires beam polarization along the momentum vector, i.e., in the horizontal plane. In the present work we analyze the source of decoherence, and investigate the way it can be suppressed in the horizontal plane in a perfectly aligned ring by means of sextupole fields. We also consider the case of an imperfect ring: transference of decoherence into the vertical plane induced by vertical plane spin precession, and the effect of sextupole fields. D. Anastassopoulos et al. AGS Proposal: Search for a permanent electric dipole moment of the deuteron nucleus at the 10 −29 e · cm level. BNL report, 2008.
DOI •	reference for this paper ※ https://doi.org/10.18429/JACoW-IPAC2019-MOPTS012
About •	paper received ※ 08 April 2019 paper accepted ※ 20 May 2019 issue date ※ 21 June 2019
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MOPTS016	Compression and Noise Reduction of Field Maps	cavity, DTL, MMI, extraction	875
	X. Du, L. Groening GSI, Darmstadt, Germany
	Errors from discretization and large data volume of field maps is a concern for beam dynamics simulations with respect to achievable accuracy and to the required amount of time. High-order singular value decomposition (HOSVD) has recently emerged as simple, effective, and adaptive tool to extract the essentials from multidimensional data. This paper is on the feasibility of compression and noise reduction of electromagnetic field map data with HOSVD. The method has been applied to an electric field map of a DTL cavity with 11 m in length comprising 55 rf-gaps. The original field map data of 220 MB was converted into practically noise-free data of just 20 KB. Noise was reduced by 95% as demonstrated using a cubic cavity for which the analytical field map is available.
DOI •	reference for this paper ※ https://doi.org/10.18429/JACoW-IPAC2019-MOPTS016
About •	paper received ※ 13 May 2019 paper accepted ※ 23 May 2019 issue date ※ 21 June 2019
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MOPTS019	End to End Simulations and Error Studies of the FAIR Proton Linac	linac, cavity, rfq, proton	885
	H. Hähnel, U. Ratzinger, M. Syha, R. Tiede IAP, Frankfurt am Main, Germany C.M. Kleffner GSI, Darmstadt, Germany
	The FAIR proton linac is developed as the high current proton injector for the future FAIR antiproton production chain at GSI. It will provide a 70 mA proton beam at an energy of 68 MeV to the SIS18 synchrotron. The linac consists of an ECR ion source, followed by a ladder RFQ and a normalconducting linac based on CH-type cavities. High beam currents and strict beam quality requirements were the main drivers for the beam dynamics design. To ensure matching between the individual sections and validate the injector design as a whole, end to end simulations were performed using TraceWin with 3D fieldmaps of the CH-linac. In this paper, the final cavity design, as well as the results of end to end simulations and error studies are discussed.
DOI •	reference for this paper ※ https://doi.org/10.18429/JACoW-IPAC2019-MOPTS019
About •	paper received ※ 13 May 2019 paper accepted ※ 20 May 2019 issue date ※ 21 June 2019
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MOPTS020	Status of the FAIR Proton LINAC	proton, linac, cavity, rfq	889
	C.M. Kleffner, S. Appel, R. Berezov, J. Fils, P. Forck, P. Gerhard, M. Kaiser, K. Knie, A. Krämer, C. Mühle, S. Puetz, A. Schnase, G. Schreiber, A. Seibel, T. Sieber, V. Srinivasan, J. Trüller, W. Vinzenz, M. Vossberg, C. Will GSI, Darmstadt, Germany H. Hähnel, U. Ratzinger, M. Schuett, M. Syha IAP, Frankfurt am Main, Germany
	For the production of Antiproton beams with sufficient intensities, a dedicated high-intensity 325 MHz Proton linac is currently under construction. The Proton linac shall deliver a beam current of up to 70 mA with an energy of 68 MeV for injection into SIS18. The source is designed for the generation of 100 mA beams. The Low-Energy Beam Transport line (LEBT) contains two magnetic solenoid lenses enclosing a diagnostics chamber, a beam chopper and a beam conus. A ladder 4-Rod RFQ and six normal conducting crossbar cavities of CCH and CH type arranged in two sections accelerate the beam to the final energy of 68 MeV. The technical design of the DTL CH cavities are presented and the commissioning measurements of the ion source are described. The construction and the procurement progress, the design and testing results of the key hardware are presented.
DOI •	reference for this paper ※ https://doi.org/10.18429/JACoW-IPAC2019-MOPTS020
About •	paper received ※ 14 May 2019 paper accepted ※ 23 May 2019 issue date ※ 21 June 2019
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MOPTS025	Overview of the ARES Bunch Compressor at SINBAD	electron, laser, plasma, linac	902
	F. Lemery University of Hamburg, Hamburg, Germany R.W. Aßmann, U. Dorda, K. Flöttmann, J. Hauser, M. Hüning, G. Kube, M. Lantschner, S. Lederer, B. Marchetti, N. Mildner, M. Pelzer, M. Rosan, J. Tiessen, K. Wittenburg DESY, Hamburg, Germany
	Funding: This project has received funding from the European Unions Horizon 2020 Research and Innovation programme under Grant Agreement No 730871. Bunch compressors are essential for the generation of short bunches with applications in e.g. colliders, free electron lasers, and advanced accelerator concepts. The up-and-coming ARES accelerator located at SINBAD, DESY will support the formation of ~100~MeV, pC, sub-fs electron bunches for LWFA research and development. We give an overview on the ARES bunch compressor, providing start-to-end simulations of the machine and an update on its technical design.
DOI •	reference for this paper ※ https://doi.org/10.18429/JACoW-IPAC2019-MOPTS025
About •	paper received ※ 17 May 2019 paper accepted ※ 20 May 2019 issue date ※ 21 June 2019
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MOPTS028	Search for Electric Dipole Moments at Cosy in Jülich - Spin-Tracking Simulations Using Bmad	dipole, storage-ring, experiment, alignment	914
	V. Poncza, A. Lehrach FZJ, Jülich, Germany A. Lehrach, V. Poncza RWTH, Aachen, Germany
	The observed matter-antimatter asymmetry in the universe cannot be explained by the Standard Model (SM) of particle physics. In order to resolve the matter dominance an additional CP violating phenomenon is needed. A candidate for physics beyond the SM is a non-vanishing Electric Dipole Moment (EDM) of subatomic particles. Since permanent EDMs violate parity and time reversal symmetries, they are also CP violating if the CPT -theorem is assumed. The JEDI (Jülich Electric Dipole moment Investigations) collaboration in Jülich is preparing a direct EDM measurement of protons and deuterons first at the storage ring COSY (COoler SYnchrotron) and later at a dedicated storage ring. In order to analyse the data and to disentangle the EDM signal from systematic effects spin tracking simulations are needed. Therefore a model of COSY was implemented using the software library Bmad. It includes the measured magnet misalignments of the latest survey and a simplified description of the RF-Wien Filter device that is used for the EDM measurement. The model was successfully benchmarked using analytical predictions of the spin behavior. A crucial point regarding the data analysis is the knowledge of the orientation of the invariant spin axis with vanishing EDM at the position of the RF-Wien Filter. Especially its radial component is unknown and spin tracking simulations can be used to determine this missing number. Tracking results as well as the algorithm to find the invariant spin axis will be presented.
DOI •	reference for this paper ※ https://doi.org/10.18429/JACoW-IPAC2019-MOPTS028
About •	paper received ※ 25 April 2019 paper accepted ※ 20 May 2019 issue date ※ 21 June 2019
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MOPTS030	Characterisation and First Beam Line Tests of the Elbe Stripline Kicker	kicker, laser, septum, neutron	918
	Ch. Schneider, A. Arnold, M. Freitag, J. Hauser, P. Michel HZDR, Dresden, Germany
	The linac based CW electron accelerator ELBE operates different secondary beamlines one at a time. For the future different end stations should be served simultaneously, hence specific bunch patterns have to be kicked into different beam-lines. The variability of the bunch pattern and the frequency resp. switching time are one of the main arguments for a stripline-kicker. A design with two tapered active electrodes and two ground fenders was optimized in time and frequency domain with the software package CST. From that a design has been transferred into a construction and was manufactured. The prototype has been tested in the laboratory and installed in the ELBE beam line. The presentation summarises the recent results and the first beam line test.
DOI •	reference for this paper ※ https://doi.org/10.18429/JACoW-IPAC2019-MOPTS030
About •	paper received ※ 10 May 2019 paper accepted ※ 20 May 2019 issue date ※ 21 June 2019
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MOPTS032	New Beam Dynamics Simulations for the FAIR p-Linac RFQ	rfq, linac, emittance, LEBT	921
	M. Syha, H. Hähnel, U. Ratzinger, M. Schuett IAP, Frankfurt am Main, Germany
	The construction of a 3.3m Ladder-RFQ at IAP, Goethe University Frankfurt, has been finished successfully last summer. This RFQ is designed to accelerate protons from 95 keV to 3.0 MeV according to the design parameters of the p-Linac at FAIR. Along the acceleration section the parameters modulation, aperture and synchronous phase are varied linearly with cell number, which differs from former designs from IAP Frankfurt. The ratio of transversal vane curvature radius to mid-cell radial aperture and the vane radius itself are constant. The development of an adequate beam dynamics design was done with the aid of the RFQGen-code and in close collaboration with the IAP resonator design team. The RFQ beam dynamics design could be successfully reproduced with the TOUTATIS-routine of CEAs TraceWin-code. Several new beam dynamics simulations were performed on the design. Among these were current and Twiss parameter studies as well as simulations concerned with the investigation of longitudinal entrance and exit gap field effects. Others were based on new measurements in the LEBT-line performed by the GSI** Ion Source Group in April 2019. In the near future, further LEBT measurements and subsequent simulations (among other to design a well-fitting cone for the RFQ), as well as mechanical error studies in TOUTATIS, will follow. Institute of Applied Physics Facility for Antiproton and Ion Research French Alternative Energies and Atomic Energy Commission **GSI Helmholtz Centre for Heavy Ion Research
DOI •	reference for this paper ※ https://doi.org/10.18429/JACoW-IPAC2019-MOPTS032
About •	paper received ※ 14 May 2019 paper accepted ※ 20 May 2019 issue date ※ 21 June 2019
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MOPTS033	RF Measurements and Tuning of the 325 MHz Ladder-RFQ	rfq, linac, operation, proton	925
	M. Schuett, U. Ratzinger, M. Syha IAP, Frankfurt am Main, Germany
	Funding: BMBF 05P15RFRBA Based on the positive results of the unmodulated 325 MHz Ladder-RFQ prototype from 2013 to 2016, we developed and designed a modulated 3.4 m Ladder-RFQ. The unmodulated Ladder-RFQ features a very constant voltage along the axis. It accepted 3 times the operating power of which is needed in operation. That level corresponds to a Kilpatrick factor of 3.1 with a pulse length of 200 µs. The 325 MHz RFQ is designed to accelerate protons from 95 keV to 3.0 MeV according to the design parameters of the proton linac within the FAIR project. This particular high frequency for a 4-ROD-RFQ creates difficulties, which triggered the development of a Ladder-RFQ with its high symmetry. The results of the unmodulated prototype have shown, that the Ladder-RFQ is very well suited for that frequency. The duty cycle is up to 5% for the applied cooling concept. Manufacturing has been completed in September 2018. We will show the finalization of assembly after manufacturing as well as low level RF measurements. The final machining step for both flatness and frequency tuning has been finished in April 2019. Journal of Physics: Conf. Series 874 (2017) 012048 **Proceedings of LINAC2016, East Lansing, TUPLR053
DOI •	reference for this paper ※ https://doi.org/10.18429/JACoW-IPAC2019-MOPTS033
About •	paper received ※ 01 May 2019 paper accepted ※ 17 May 2019 issue date ※ 21 June 2019
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MOPTS036	RFQ Electrodes Change and Upgrade Option at the UNILAC HSI Injector	rfq, operation, cavity, MMI	936
	M. Vossberg, P. Gerhard, L. Groening, S. Mickat, H. Vormann, C. Xiao GSI, Darmstadt, Germany V. Bencini, J.M. Garland, J.-B. Lallement, A.M. Lombardi CERN, Geneva, Switzerland
	In order to meet the beam intensity and quality requirements imposed by FAIR, the HSI-RFQ beam dynamics originally dating from 2009 has been re-designed recently at CERN. Front-to-end simulations demonstrated that the new design meets the FAIR targets. Implementation of the new electrodes, initially planned for 2019, will require re-adaption of the RFQ cavity rf-parameters by re-shaping the stems that keep the electrodes. However, during the beam time 2018 the existing RFQ did not reach its nominal voltage most likely due to expired lifetime of the electrodes originating from 2009. In order to shorten the RFQ maintenance period and to minimize any risk for upcoming beam time 2019, it was decided to post-pone the implementation of the new design and rather just re-producing the 2009 design electrodes. This contribution is on the re-production process as short-term solution and on the full implementation of the new design as mid-term solution. CST simulations performed at GSI assure that the resonance frequency with the new electrode geometry is recuperated through corrections of the carrier rings. The status of the exchange of the electrodes and simulations for the adaptation of the new electrode design are presented.
DOI •	reference for this paper ※ https://doi.org/10.18429/JACoW-IPAC2019-MOPTS036
About •	paper received ※ 13 May 2019 paper accepted ※ 17 May 2019 issue date ※ 21 June 2019
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MOPTS037	Comparison Between Measurement and Simulation of a Full Scale Prototype for the Proton Injector at FAIR	cavity, proton, linac, resonance	940
	A. Seibel, C.M. Kleffner, K. Knie, M. Vossberg GSI, Darmstadt, Germany U. Ratzinger IAP, Frankfurt am Main, Germany
	A dedicated 68 MeV, 70 mA proton injector is required for the research program at FAIR (Facility for Antiproton and Ion Research). This 325 MHz linear injector contains a RFQ and six CH structures. The CH (Crossbar H-mode) structures are working in the H₂10 mode. The main acceleration of this room temperature linac will be provided by the CH structures. For the second acceleration from 11.5 MeV to 24.2 MeV a full scale prototype has been built. This structure consists of two individual CH resonators and a coupling cell. Inside the structure there are 17 tuners, they have an impact on the electric field and the frequency. For operation a flat field is required, therefore this tuners must be correctly positioned. Some series of low level tuning and frequency measurements were done to determine the size of the tuners. Low level measurements and simulations will be compared and presented.

Paper

Title

Other Keywords

Page

MOPGW003

Collective Instability Studies for Sirius

impedance, storage-ring, radiation, coupling

61

F.H. de Sá
LNLS, Campinas, Brazil

In this work we will present the estimates of single and multi-bunch instability thresholds and current-dependent effects, such as tune-shifts and potential-well distortion for the Sirius storage ring. The results were obtained by tracking simulations and semi-analytic methods using the updated and detailed impedance budget of the machine, which includes contributions from all the in-vacuum components and the coherent synchrotron radiation (CSR) impedance.

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reference for this paper ※ https://doi.org/10.18429/JACoW-IPAC2019-MOPGW003

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paper received ※ 15 May 2019 paper accepted ※ 18 May 2019 issue date ※ 21 June 2019

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MOPGW012

Study of Fringe Fields Effects from Final Focus Quadrupoles on Beam Based Measured Quantities

quadrupole, multipole, optics, dynamic-aperture

90

T. Pugnat, B. Dalena
CEA-IRFU, Gif-sur-Yvette, France
L. Bonaventura, A. Simona
Politecnico di Milano, Milano, Italy
R. De Maria, V.K.B. Olsen
CERN, Geneva, Switzerland

Accelerator physics needs advanced modeling and simulation techniques, in particular for beam stability studies. A deeper understanding of the effects of magnetic fields non-linearities will greatly help in the improvement of future colliders design and performance. In *, a new tracking method was proposed to study the effect of the longitudinal dependency of the harmonics on the beam dynamics. In this paper, the study will focus on the effects on observable quantities in beam based measurements, for the case of HL-LHC Inner Triplet and with possible tests in LHC.
* T. Pugnat et al., "Accurate and Efficient Tracking in Electromagnetic Quadrupoles", in Proc. IPAC’18, Vancouver, Canada, June 2018, paper THPAK004, pp. 3207.

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paper received ※ 14 May 2019 paper accepted ※ 22 May 2019 issue date ※ 21 June 2019

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MOPGW019

Beam-Beam Blowup Issue After Low Emittance Tuning for FCC-ee

emittance, lattice, optics, coupling

112

D. El Khechen, K. Oide, F. Zimmermann
CERN, Geneva, Switzerland
K. Oide
KEK, Ibaraki, Japan

FCC-ee (Future Circular Collider) is a 100 km electron-positron circular collider with two foreseen experiments, aiming to run at four energies for precision studies of the Z, W, and Higgs boson and the top quark. The FCC-ee is a challenging machine from different points of view. In particular the beam-beam effects are of great importance. For the FCC-ee high-luminosity operation, the beam-beam effects impose profound constraints on the operating point in betatron tune space. In addition, taking into account different sources of machine nonlinearities, a tracking simulation with beam-beam elements revealed a strong beam blowup, especially in the vertical plane. Such a blowup is a potential obstacle to achieving and maintaining a high luminosity; therefore it needs to be carefully studied. In this paper, we present a general overview of simulation results on the FCC-ee beam-beam blowup with realistic machine errors.

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reference for this paper ※ https://doi.org/10.18429/JACoW-IPAC2019-MOPGW019

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paper received ※ 10 May 2019 paper accepted ※ 20 May 2019 issue date ※ 21 June 2019

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MOPGW025

Beam Breakup Simulations for the Mainz Energy Recovering Superconducting Accelerator MESA

cavity, HOM, cryomodule, operation

135

C.P. Stoll, F. Hug
KPH, Mainz, Germany

Funding: This work is supported by DFG through PRISMA+ cluster of excellence EXC 2118/2019, RTG 2128 and by the European Union’s Horizon 2020 Research and Innovation programme under Grant Agreement No 730871.
MESA is a two pass energy recovery linac (ERL) currently under construction at the Johannes Gutenberg-University in Mainz. MESA uses four 1.3 GHz TESLA type cavities with 12.5 MV/m of accelerating gradient in two modified ELBE type cryomodule with improved thermal connection of the HOM antennas and cw operation. In the first stage of MESA operation 1mA of beam current is foreseen, which will later be upgraded to 10mA. One potential limit to maximum beam current in ERLs is the transverse beam breakup (BBU) instability induced by dipole Higher Order Modes (HOMs). These modes can be excited by bunches passing through the cavities off axis. Following bunches are then deflected by the HOMs, which results in even larger offsets for recirculated bunches. This feedback can even lead to beam loss. Simulation results for HOM spectra of a single TESLA cavity are available for example in *. It was possible to measure the HOM spectra in the cold, not tuned cavities at DESY and in the cold string tuned to the 1.3 GHz fundamental mode at Mainz. Results for the maximum beam current for MESA, limited by BBU, for the various HOM spectra are presented.
* "Eigenmode Calculations for the TESLA Cavity Considering Wave-Propagation Losses through Fundamental and Higher-Order Mode Couplers", W. Ackermann, H. De Gersem, C. Liu, and T. Weiland

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reference for this paper ※ https://doi.org/10.18429/JACoW-IPAC2019-MOPGW025

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paper received ※ 16 April 2019 paper accepted ※ 20 May 2019 issue date ※ 21 June 2019

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MOPGW026

Transfer Line Optics Design Using Machine Learning Techniques

target, quadrupole, optics, operation

139

D.M. Vilsmeier
IAP, Frankfurt am Main, Germany
M. Bai, M. Sapinski
GSI, Darmstadt, Germany

Optimization of transfer line optics is essential for delivering high quality beams to the experimental areas. This type of optimization is usually done by hand and relies on the experience of operators. The nature of this task is repetitive though highly complex. Besides optimizing the beam quality at the experiments this task is often accompanied by secondary objectives or requirements such as keeping the beam losses below an acceptable threshold. In the past years Deep Learning algorithms have experienced a rapid development and gave rise to various advanced software implementations which allow for straightforward usage of corresponding techniques, such as automatic differentiation and gradient backpropagation. We investigate the applicability and performance of these techniques in the field of transfer line optics optimization, specifically for the HADES beamline at GSI, in form of gradient-based differentiable simulators. We test our setup on results obtained from MADX simulations and compare our findings to different gradient-free optimization methods. Successfully employing such methods relieves operators from the tedious optimization tasks.

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reference for this paper ※ https://doi.org/10.18429/JACoW-IPAC2019-MOPGW026

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paper received ※ 15 May 2019 paper accepted ※ 20 May 2019 issue date ※ 21 June 2019

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MOPGW030

New Analytical Derivation of Group Velocity in TW Accelerating Structures

cavity, dipole, polarization, coupling

155

M. Behtouei, M. Migliorati, L. Palumbo
Sapienza University of Rome, Rome, Italy
L. Faillace
Universita’ degli Studi di Milano & INFN, Milano, Italy
B. Spataro
INFN/LNF, Frascati, Italy

Ultra high-gradient accelerating structures are needed for the next generation of compact light sources. In the framework of the Compact Light XLS project, we are studying a high harmonic traveling-wave accelerating structure operating at a frequency of 35.982 GHz, in order to linearize the longitudinal space phase. In this paper, we propose a new analytical approach for the estimation of the group velocity in the structure and we compare it with numerical electromagnetic simulations that are carried out by using the code HFSS in the frequency domain.

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reference for this paper ※ https://doi.org/10.18429/JACoW-IPAC2019-MOPGW030

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paper received ※ 08 April 2019 paper accepted ※ 20 May 2019 issue date ※ 21 June 2019

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MOPGW035

Coupling Impedance of the Collimator Without RF-Shields at the RCS in J-PARC

impedance, synchrotron, collimation, proton

163

Y. Shobuda, J. Kamiya, K. Moriya, K. Okabe
JAEA/J-PARC, Tokai-Mura, Naka-Gun, Ibaraki-Ken, Japan

All holes on the chamber walls of synchrotrons should be filled with the radiofrequency (RF)-shields to suppress coupling impedances that excite beam instabilities. In a synchrotron, titanium nitride (TiN)-coated RF-shields are installed with collimators. If the holes, through which the collimator jaw enters and exits the chamber, are filled with such RF-shields, the shields may break down as the dynamic coefficient of TiN increases in vacuum. At the Rapid Cycling Synchrotron (RCS), the RF-shields are eliminated from the collimator after demonstrating that the effect due to the RF-shields is negligible on the impedance at low frequencies.

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reference for this paper ※ https://doi.org/10.18429/JACoW-IPAC2019-MOPGW035

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paper received ※ 28 April 2019 paper accepted ※ 18 May 2019 issue date ※ 21 June 2019

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MOPGW037

Dynamic Variation of Chromaticity for Beam Instability Mitigation in the 3-GeV RCS of J-PARC

emittance, extraction, injection, impedance

171

P.K. Saha, H. Harada, H. Hotchi, Y. Shobuda, T. Takayanagi, F. Tamura, Y. Watanabe
JAEA/J-PARC, Tokai-Mura, Naka-Gun, Ibaraki-Ken, Japan

We have studied many other dynamic approaches from that reported in the IPAC 2018 for transverse beam instability mitigation in the presence of strong space charge in the 3-GeV RCS of J-PARC. One of such a method is the introduction of an excess of chromaticity from that of natural chromaticity by reversing the sextupole magnetic fields from the middle of the acceleration cycle. The benifits of this method are twofold. It allows to utilize sextupole for chromaticty correction at lower energy and also mitigate the beam instability at higher energy because of introducing higher chromaticity. We first carried out numerical simulations by using ORBIT code, experimentally verified and then applied for the machine operation. The detail of simulation and measurements results are presented in this paper.

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reference for this paper ※ https://doi.org/10.18429/JACoW-IPAC2019-MOPGW037

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paper received ※ 14 May 2019 paper accepted ※ 23 May 2019 issue date ※ 21 June 2019

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MOPGW038

Collimator’s Impact Into the Transverse Emittance Growth at KEK Compact ERL

wakefield, emittance, operation, FEL

174

O.A. Tanaka, T. Miyajima, N. Nakamura, T. Obina, M. Shimada, Y. Tanimoto
KEK, Ibaraki, Japan

In high-intensity particle accelerators, unwanted trans-verse and longitudinal wakefields arise when the high-charge particle beam passes through the narrow chambers or locations with small transverse apertures, such as collimator jaws. Transverse wakefields impose a transverse kicks to the beam, changing its shape, and leading to the growth of the transverse emittance. Longitudinal wakes cause the beam energy losses, heating of the narrow chambers etc. In the present study we investigated the collimator’s impact to the beam. Thus, we evaluated the collimator’s wakefields through the CST simulations. We estimated the corresponding transverse kicks and longitudinal wakes. In the summary simulation results were cross-checked with correspondent analytical expressions.

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paper received ※ 15 May 2019 paper accepted ※ 21 May 2019 issue date ※ 21 June 2019

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MOPGW047

Analysis and Simulation of the "After-Pulse" RF Breakdown

cavity, timing, GUI, experiment

196

X. Lin, H.B. Chen, Z.N. Liu, J. Shi, H. Zha
TUB, Beijing, People’s Republic of China
X.W. Wu
CERN, Meyrin, Switzerland

During the high power experiment of a single-cell standing-wave accelerating structure, it was observed that many RF breakdowns happen when the field inside cavity is decaying after the input rf pulse is off. The distribution of breakdown timing shows a peak at the moment of RF power switches off. A series of simulation was performed to study the after-pulse breakdown effect in such a standing-wave structure. A method of calculating poynting vector over time is proposed in this article to study the modified poynting vector at critical points in the cavity. Field simulation and thermal simulation were also carried out to analyse possible reasons for the after-pulse breakdown effect.

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reference for this paper ※ https://doi.org/10.18429/JACoW-IPAC2019-MOPGW047

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paper received ※ 14 May 2019 paper accepted ※ 17 May 2019 issue date ※ 21 June 2019

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MOPGW052

The Study of Single-Bunch Instabilities in the Ramping Process in the HEPS Booster

booster, impedance, lattice, injection

206

H.S. Xu, Y.M. Peng, N. Wang
IHEP, Beijing, People’s Republic of China

The booster of High Energy Photon Source (HEPS) is proposed to ramp the beam energy from 500 MeV to 6 GeV, and to deliver the required charge to the storage ring. However, the transverse single-bunch instability may limit the reachable bunch charge in the booster. The study of the transverse single-bunch instability has been carried out for the HEPS booster at both 500 MeV and 6 GeV to double check whether the required single-bunch charge can be achieved. Furthermore, the energy ramping process was recently included in the study. We concentrate in the analyses of the simulation results with the consideration of energy ramping process in this paper.

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reference for this paper ※ https://doi.org/10.18429/JACoW-IPAC2019-MOPGW052

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paper received ※ 15 May 2019 paper accepted ※ 20 May 2019 issue date ※ 21 June 2019

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MOPGW062

Radiation of a Charge Moving in a Wire Structure

radiation, FEL, lattice, electron

231

S.N. Galyamin, A.V. Tyukhtin, V.V. Vorobev
Saint Petersburg State University, Saint Petersburg, Russia
A.I. Benediktovitch
EuXFEL, Hamburg, Germany
A.I. Benediktovitch
BSU, Minsk, Belarus, Belarus

Funding: This work is supported by the grant from Russian Foundation for Basic Research (No. 17-52-04107).
In the X-ray frequency region, interaction of relativistic electrons with crystals results in parametric X-ray radiation (PXR), with its frequency being determined by distance between crystallographic planes and direction of electron motion. If instead of crystal one considers an artificial periodic structure with periods of the order of mm, one can expect emission of radiation of a similar nature at terahertz (THz) frequencies. This frequency range is of significant interest during last decade due to its prospective applications. Moreover, artificial wire-like structures are considered as a promising alternative to conventional dielectric structures for wakefield acceleration*. Here we consider electromagnetic (EM) field produced by a charged particle bunch moving through a lattice of parallel conducting wires. We present several approaches for analysis of EM field in the described wire structure. First, conventional two-wave approximation for describing the "short-wave response" is developed. Second, we use the effective medium approach and describe the "long-wave" part of the spectrum. Third, we develop a method based on vibrator antenna theory which can be useful for finite length wire structure.
* P.D. Hoang, et al., Phys. Rev. Lett., V. 120, P. 164801 (2018).

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paper received ※ 14 May 2019 paper accepted ※ 20 May 2019 issue date ※ 21 June 2019

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MOPGW066

Local Impedance Measurements Using the Orbit Bump Method at ALBA

impedance, storage-ring, betatron, vacuum

240

Z. Martí, G. Benedetti, T.F.G. Günzel, U. Iriso
ALBA-CELLS Synchrotron, Cerdanyola del Vallès, Spain

The orbit bump technique has been used at the ALBA Storage Ring to characterize with good precision the impedance of single machine elements, like the in-vacuum undulators or the CLIC stripline kicker. The results are compared with theoretical studies, as well as impedance measurements done at ALBA using other methods like the turn by turn betatron phase or from the analysis of the detuning slopes of the Transverse Mode Coupling Instability.

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paper received ※ 14 May 2019 paper accepted ※ 17 May 2019 issue date ※ 21 June 2019

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MOPGW067

On Coordinate Systems in Beam Dynamics

GUI, experiment, acceleration, FEL

243

E. Laface
ESS, Lund, Sweden

Any description of the beam dynamics calculation and simulation relies on the proper choice of a coordinate system in order to minimize the computational complexity and to apply different level of approximations in the calculations. This need generates a large number of reference systems, especially to describe the longitudinal dynamics of a particle beam like(z, z′),(t,∆P/P),(z, φ), etc. In this paper we summarize the rules to change coordinates systems, which system is canonical and how the Hamiltonian of the beam transforms according to the chosen coordinate system.

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paper received ※ 10 May 2019 paper accepted ※ 20 May 2019 issue date ※ 21 June 2019

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MOPGW068

Crosstalk of Beam-Beam Effect and Longitudinal Impedance at CEPC

impedance, luminosity, collider, factory

247

Y. Zhang, N. Wang, C.H. Yu
IHEP, Beijing, People’s Republic of China
C.T. Lin
University of Chinese Academy of Sciences, Beijing, People’s Republic of China

Funding: Project 11775238 supported by NSFC
In conventional e⁺e⁻ storage ring colliders, we only use lengthend bunch length in beam-beam simulation instead of considering impedance directly. It is no problem since the longitudinal dynamics is not sensitive to beam-beam interaction. But it is different since the bunch will also be lengthend during beam-beam interaction by beamstrahlung effect. It is very natural and more self-consistent to consider the longitudinal impedance in the beam-beam simulation. The simulation shows that the working point region of stable collision is slightly shifted by the longitudinal impedance. It is found that the vertical coherent oscillation may decreases the beam-beam limit with impedance at some working point.

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reference for this paper ※ https://doi.org/10.18429/JACoW-IPAC2019-MOPGW068

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paper received ※ 15 May 2019 paper accepted ※ 20 May 2019 issue date ※ 21 June 2019

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MOPGW070

Longitudinal Stability of the Hollow Ion Bunches After Momentum Slip-Stacking in the CERN SPS

emittance, damping, synchrotron, proton

254

T. Argyropoulos, A. Lasheen, D. Quartullo, E.N. Shaposhnikova
CERN, Geneva, Switzerland

Momentum slip-stacking is planned to be used for the lead ion beams in the CERN SPS to double the beam intensity for the High-Luminosity LHC project. During this RF manipulation two SPS batches, controlled by two independent RF systems, are going to be interleaved on an intermediate energy plateau, reducing the bunch spacing from 100 to 50 ns. However, there are limitations how close the frequencies of two RF systems can approach each other, resulting in a hole in the longitudinal bunch particle distribution due to the offset in energy of the recaptured bunches. After filamentation, these bunches should be further accelerated to the SPS top energy, before extraction to the LHC. Macro-particle simulations have shown that Landau damping is lost for the bunches with the smallest longitudinal emittances in the batch, causing un-damped oscillations of the bunch core after recapture. The standard application of an additional, fourth harmonic RF system, successfully used in proton operation, was not able to damp the oscillations at top energy, while it was necessary to switch it on from the moment of recapture. In this paper the longitudinal stability of the bunches after slip-stacking is studied in more details both by macro-particle simulations and analytical calculations.

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reference for this paper ※ https://doi.org/10.18429/JACoW-IPAC2019-MOPGW070

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paper received ※ 15 May 2019 paper accepted ※ 22 May 2019 issue date ※ 21 June 2019

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MOPGW073

Beam Manipulation Using Self-Induced Fields at the SwissFEL Injector

FEL, electron, experiment, wakefield

266

S. Bettoni, P. Craievich, E. Ferrari, R. Ganter, F. Marcellini, E. Prat, S. Reiche
PSI, Villigen PSI, Switzerland
A.A. Lutman
SLAC, Menlo Park, California, USA
G. Penco
Elettra-Sincrotrone Trieste S.C.p.A., Basovizza, Italy

In the past years wakefield sources have been used to manipulate electron beams in accelerators. We recently installed corrugated structures for a total length of 2~m at the SwissFEL injector to test novel schemes for beam manipulations. We present simulations and early experimental results. We compare the model predictions with the measured data for the bunch energy losses and the kick factor, and show early results for the longitudinal phase space linearization and the production of current spikes.

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reference for this paper ※ https://doi.org/10.18429/JACoW-IPAC2019-MOPGW073

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paper received ※ 09 May 2019 paper accepted ※ 20 May 2019 issue date ※ 21 June 2019

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MOPGW076

Verification by RF Measurements of New HOM Mitigation Scheme Developed for Future SPS 33-Cell Accelerating Structures

HOM, damping, impedance, coupling

274

P. Kramer, A. Farricker, C. Vollinger
CERN, Geneva, Switzerland

Longitudinal higher-order modes (HOMs) at a frequency of around 630 MHz in the 200 MHz travelling wave RF structures currently limit the beam intensities in the CERN SPS to less than that required by the High Luminosity (HL-) LHC. In the framework of the LHC Injectors Upgrade (LIU) project, the performance of the already existing HOM damping scheme for these standing wave modes must be improved. This involves improving the existing HOM-couplers as well as the possible use of a new mitigation technique via the insertion of resonant posts in some cells of the multi-cell structures. The development of the new damping scheme has been performed using theoretical analysis of the cavity-coupler interaction in conjunction with full-wave electromagnetic (EM) field simulations. This contribution will show the verification of the improved HOM damping performance by measurements on a single section with 11 cells and on the future 33-cell structures. The parasitic impact of the damping scheme on the travelling wave fundamental passband (FPB) will also be presented.

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reference for this paper ※ https://doi.org/10.18429/JACoW-IPAC2019-MOPGW076

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paper received ※ 11 May 2019 paper accepted ※ 20 May 2019 issue date ※ 21 June 2019

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MOPGW078

Change of Beam Distribution Due to Decoherence in the Presence of Transverse Feedback

feedback, octupole, damping, emittance

281

S.V. Furuseth, X. Buffat
CERN, Geneva, Switzerland
S.V. Furuseth
EPFL, Lausanne, Switzerland

The effect of Landau damping is often calculated based on a Gaussian beam distribution in all degrees of freedom. The stability of the beam is however strongly dependent on the details of the distribution. The present study focuses on the change of bunch distributions caused by the decoherence of the excitation driven by an external source of noise, in the presence of both amplitude detuning and a transverse feedback. Both multiparticle tracking simulations and theoretical models show a similar change of the distribution. The possible loss of Landau damping driven by this change is discussed.

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reference for this paper ※ https://doi.org/10.18429/JACoW-IPAC2019-MOPGW078

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paper received ※ 08 April 2019 paper accepted ※ 19 May 2019 issue date ※ 21 June 2019

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MOPGW082

Mitigation of Stray Magnetic Field Effects in CLIC with Passive Shielding

shielding, feedback, collider, hadron

293

C. Gohil, N. Blaskovic Kraljevic, D. Schulte
CERN, Meyrin, Switzerland
P. Burrows
JAI, Oxford, United Kingdom

Simulations have shown the Compact Linear Collider (CLIC) is sensitive to external dynamic magnetic fields (stray fields) to the nT level. Due to these extremely tight tolerances, mitigation techniques will be required to prevent performance loss. A passive shielding technique is envisaged as a potential solution. A model for passive shielding is presented along with calculations of its transfer function. Measurements of the transfer function of a promising material (mu-metal) that can be used for passive shielding are presented. The validity of passive shielding models in small amplitude magnetic fields is also discussed.

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reference for this paper ※ https://doi.org/10.18429/JACoW-IPAC2019-MOPGW082

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paper received ※ 01 May 2019 paper accepted ※ 20 May 2019 issue date ※ 21 June 2019

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MOPGW085

Intensity Dependent Effects in the ILC BDS

wakefield, luminosity, collider, linear-collider

305

P. Korysko, A. Latina
CERN, Geneva, Switzerland
P. Burrows
Oxford University, Physics Department, Oxford, Oxon, United Kingdom

The International Linear Collider (ILC) is an electron-positron collider being considered for the post-LHC era. Its Beam Delivery System (BDS) receives the beam from the main linac. This beam is then focused to the nanometer scale after going through collimators, beam diagnostic systems, strong magnets, etc. Effects such as wakefields due to resistive-wall, BPMs and collimators make the system very sensitive to the beam intensity. Understanding these effects is crucial in order to demonstrate that the nominal beam size at the Interaction Point (IP) can be reached in realistic scenarios. In this paper, results of the intensity dependence effects in the ILC BDS, simulated with PLACET, are presented.

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reference for this paper ※ https://doi.org/10.18429/JACoW-IPAC2019-MOPGW085

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paper received ※ 23 April 2019 paper accepted ※ 20 May 2019 issue date ※ 21 June 2019

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MOPGW086

Intensity Dependent Effects at ATF2, KEK

collider, linear-collider, wakefield, electron

308

P. Korysko, A. Latina
CERN, Geneva, Switzerland
P. Burrows
Oxford University, Physics Department, Oxford, Oxon, United Kingdom
A. Faus-Golfe
LAL, Orsay, France
K. Kubo, T. Okugi
KEK, Ibaraki, Japan

The Accelerator Test Facility 2 (ATF2) at KEK is a prototype for the Final Focus Systems of the future e⁺e⁻ linear colliders, the International Linear Collider (ILC) and the Compact Linear Collider (CLIC). In this paper both simulation and experimental results are presented with special emphasis on intensity-dependent effects. The importance of these effects is shown using the PLACET code and realistic ATF2 machine simulations (including beam jitter, misalignment, wakefield, Beam Based Alignment (BBA) correction, …). The latest experimental results are also presented, in particular the impact of the beam intensity on the beam size at the IP.

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reference for this paper ※ https://doi.org/10.18429/JACoW-IPAC2019-MOPGW086

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paper received ※ 23 April 2019 paper accepted ※ 20 May 2019 issue date ※ 21 June 2019

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MOPGW087

GALACTIC and GALACLIC: Two Vlasov Solvers for the Transverse and Longitudinal Planes

impedance, synchrotron, resonance, coupling

312

E. Métral
CERN, Geneva, Switzerland

GALACTIC and GALACLIC, two Vlasov solvers for the study, in the transverse and longitudinal plane respectively, of single-bunch coherent oscillation modes, were recently developed starting from the Vlasov equation and using a decomposition on the low-intensity eigenvectors, as proposed by Laclare and Garnier. The first Vlasov solver was used for instance to shed light on the destabilising effect of resistive transverse dampers and the second helped understanding the details of the mode-coupling behind some longitudinal microwave instabilities. Both theories are reviewed in detail, highlighting in particular the similarities and peculiarities of the two approaches.

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reference for this paper ※ https://doi.org/10.18429/JACoW-IPAC2019-MOPGW087

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paper received ※ 23 April 2019 paper accepted ※ 20 May 2019 issue date ※ 21 June 2019

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MOPGW088

A Two-Mode Model to Study the Effect of Space Charge on TMCI in the "Long-Bunch" Regime

coupling, space-charge, impedance, optics

316

E. Métral
CERN, Geneva, Switzerland

Using a two-mode approach for the Transverse Mode-Coupling Instability (TMCI) in the ’short-bunch’ regime (where the mode-coupling takes place between the modes 0 and -1, such as in the CERN LHC), both a reactive damper (ReaD) and Space Charge (SC) are expected to be beneficial: the ReaD would shift the mode 0 up while SC would shift the mode -1 down, but in both cases the coupling (and related instability) would occur at higher intensities. However, the situation is more involved in the ’long-bunch’ regime (where the mode-coupling takes place between higher-order modes, such as in the CERN SPS). As the ReaD modifies only the (main) mode 0 and not the others, it is expected to have no effect for the main mode-coupling. As concerns SC, it modifies all the modes except the mode 0, and the result has been a subject of discussion for two decades. A two-mode approach is discussed in detail in this contribution for the case of a single bunch interacting with a broad-band resonator impedance in the ’long-bunch’ regime. This model reveals in particular that in the presence of space charge, the intensity threshold can only be similar to or lower than that in the absence of space charge.

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reference for this paper ※ https://doi.org/10.18429/JACoW-IPAC2019-MOPGW088

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paper received ※ 23 April 2019 paper accepted ※ 23 May 2019 issue date ※ 21 June 2019

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MOPGW089

Longitudinal Mode-Coupling Instability: GALACLIC Vlasov Solver vs. Macroparticle Tracking Simulations

impedance, coupling, synchrotron, proton

320

E. Métral
CERN, Geneva, Switzerland
M. Migliorati
Rome University La Sapienza, Roma, Italy
M. Migliorati
INFN-Roma1, Rome, Italy

Following the same approach as for the recently developed GALACTIC Vlasov solver in the transverse plane and taking into account the potential-well distortion, a new Vlasov solver, called GALACLIC, was developed for the longitudinal plane. In parallel, a new mode analysis was implemented for the post-processing of the results obtained through macroparticle tracking simulations. The results of the several benchmarks performed between the two methods are presented.

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reference for this paper ※ https://doi.org/10.18429/JACoW-IPAC2019-MOPGW089

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paper received ※ 23 April 2019 paper accepted ※ 23 May 2019 issue date ※ 21 June 2019

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MOPGW095

Beam Dynamics Simulations with Crab Cavities in the SPS Machine

multipole, cavity, luminosity, optics

342

A. Alekou, A. Alekou, H. Bartosik, H. Bartosik, M. Carlà, Y. Papaphilippou, Y. Papaphilippou, Y. Papaphilippou
CERN, Meyrin, Switzerland
A. Alekou, A. Alekou, R.B. Appleby, R.B. Appleby
UMAN, Manchester, United Kingdom
R.B. Appleby
Cockcroft Institute, Warrington, Cheshire, United Kingdom

The LHC Upgrade, called High Luminosity LHC, aims to increase the integrated luminosity by a factor of 10. To achieve this, the project relies on a number of key innovative technologies, including the use of superconducting Crab Cavities with ultra-precise phase control for beam rotation. A set of prototype Crab Cavities has been recently installed in the second largest machine of CERN, the Super Proton Synchrotron (SPS), that operated as a test-bed from May to November of 2018. The tight LHC constraints call for axially non-symmetric cavity designs that introduce high order multipole components. Furthermore, the Crab Cavities in the presence of SPS non-linearities can affect the long term stability of the beam. This paper presents how the SPS dynamic aperture is affected for different cavity, machine and beam configurations.

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reference for this paper ※ https://doi.org/10.18429/JACoW-IPAC2019-MOPGW095

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paper received ※ 06 May 2019 paper accepted ※ 20 May 2019 issue date ※ 21 June 2019

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MOPGW098

Iterative Trajectory-Correction Scheme for the Early Commissioning of Diffraction-Limited Light Sources

MMI, lattice, feedback, storage-ring

353

Ph. Amstutz, T. Hellert
LBNL, Berkeley, USA

The commissioning of diffraction-limited light sources will be significantly affected by the fact that typical lattice designs rely on very strong focussing elements in order to achieve the small emittance goals. Especially in the early-commissioning phase this can render procedures successfully used in the commissioning of existing third-generation light sources ill-suited for the application to these new machines. In this contribution we discuss an iterative approach to the early trajectory correction, based on the well-known pseudo-inversion of a trajectory-response matrix. Measuring this matrix during early commissioning can be cumbersome, so that an algorithm working with the model response matrix of the lattice is desirable. We discuss the stability of the iteration in the presence of lattice errors, resulting in differences between the actual and the model response matrix. Further, Tikhonov regularization is investigated as a means to trade off the RMS trajectory variation against the strength of the required corrector kicks.

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reference for this paper ※ https://doi.org/10.18429/JACoW-IPAC2019-MOPGW098

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paper received ※ 14 May 2019 paper accepted ※ 23 May 2019 issue date ※ 21 June 2019

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MOPGW099

Vlasov-Fokker-Planck Simulations of Passive Higher-Harmonic Cavity Effects in ALS-U

cavity, impedance, synchrotron, resonance

357

G. Bassi
BNL, Upton, Long Island, New York, USA

Funding: Work supported by DOE under contract DE-SC0012704
We discuss numerical simulations of the Vlasov-Fokker-Planck equation to model passive higher-harmonic cavity (HHC) effects with parameters of the Advanced Light Source Upgrade (ALS-U. The numerical results, obtained with the SPACE code, are compared with a modal analysis of the coupled-bunch instability theory.

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reference for this paper ※ https://doi.org/10.18429/JACoW-IPAC2019-MOPGW099

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paper received ※ 18 May 2019 paper accepted ※ 24 May 2019 issue date ※ 21 June 2019

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MOPGW104

Equilibria and Synchrotron Stability in Two Energy Storage Rings

electron, storage-ring, damping, focusing

364

B. Dhital, J.R. Delayen, G.A. Krafft
ODU, Norfolk, Virginia, USA
J.R. Delayen, Y.S. Derbenev, D. Douglas, G.A. Krafft, F. Lin, V.S. Morozov, Y. Zhang
JLab, Newport News, Virginia, USA

In a dual energy storage ring, the electron beam passes through two loops at markedly different energies E_L, and E_H, i.e., energies for low energy loop and high energy loop respectively. These loops use a common beamline where a superconducting linac at first accelerates the beam from EL to EH and then decelerates the beam from EH to EL in the next pass. There are two basic solutions to the equilibrium problems possible, i.e., ’Storage Ring’ (SR) equilibrium and ’Energy Recovery Linac’ (ERL) equilibrium. SR equilibrium mode more resembles the usual single loop storage ring with strong synchrotron motion and ERL equilibrium mode is the case where RF in two beam passes nearly cancels. Calculations based on linear transfer matrix formalism show that longitudinal stability exists for both SR mode and ERL mode in two energy storage rings.

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reference for this paper ※ https://doi.org/10.18429/JACoW-IPAC2019-MOPGW104

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paper received ※ 14 May 2019 paper accepted ※ 18 May 2019 issue date ※ 21 June 2019

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MOPGW122

Beam-based Measurement of Broadband Longitudinal Impedance at NSLS-II

impedance, vacuum, diagnostics, storage-ring

400

V.V. Smaluk, B. Bacha, G. Bassi, A. Blednykh
BNL, Upton, Long Island, New York, USA

Funding: Department of Energy Contract No. DE-SC0012704
Interaction of a particle beam with the vacuum chamber impedance is one of the main effects limiting the beam intensity in accelerators. Minimization of the impedance is an essential part of the vacuum chamber design for any new accelerator project. The impedance can be estimated experimentally by measuring beam dynamics effects caused by the beam-impedance interaction. Experience obtained at many accelerator facilities shows the beam-based measurements are often different from the pre-computed impedance budgets, the discrepancy of a factor of two or even more is not unusual. The measurements of broadband longitudinal impedance carried out at NSLS-II are discussed in comparison with the numerically simulated impedance budget.

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reference for this paper ※ https://doi.org/10.18429/JACoW-IPAC2019-MOPGW122

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paper received ※ 15 May 2019 paper accepted ※ 23 May 2019 issue date ※ 21 June 2019

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MOPGW124

Coherent Synchrotron Radiation Simulation for CBETA

linac, lattice, radiation, shielding

406

W. Lou, C.M. Gulliford, G.H. Hoffstaetter, D. Sagan
Cornell University (CLASSE), Cornell Laboratory for Accelerator-Based Sciences and Education, Ithaca, New York, USA
C.E. Mayes
SLAC, Menlo Park, California, USA
N. Tsoupas
BNL, Upton, Long Island, New York, USA

CBETA is an energy recovery linac accelerating from 6 MeV to 150 MeV in four linac passes, using a single return beamline accepting all energies from 42 to 150 MeV. While CBETA gives promise to deliver unprecedentedly high beam current with simultaneously small emittance, Coherent Synchrotron Radiation (CSR) can pose detrimental effect on the beam at high bunch charges and short bunch lengths. To investigate the CSR effects on CBETA, we used the established simulation code Bmad to track a bunch with different parameters. We found that CSR causes phase space dilution, and the effect becomes more significant as the bunch charge and recirculation pass increase. Potential ways to mitigate the effect involving vacuum chamber shielding and increasing bunch length are being investigated.

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reference for this paper ※ https://doi.org/10.18429/JACoW-IPAC2019-MOPGW124

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paper received ※ 15 May 2019 paper accepted ※ 20 May 2019 issue date ※ 21 June 2019

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MOPGW128

Simulation and Analysis of Wake Fields and Trapped RF Modes in Insertion Device Vacuum Chambers at the Canadian Light Source

vacuum, undulator, insertion-device, insertion

414

E.J. Ericson, D. Bertwistle, M.J. Boland
CLS, Saskatoon, Saskatchewan, Canada
M.J. Boland, M. Castillo Sosa
University of Saskatchewan, Saskatoon, Canada
D. Pelz
RFS, Kilsyth, Australia

Funding: CFI, NSERC, NRC, CIHR, the Province of Saskatchewan, WD, WESTGRID, Compute Canada, and the University of Saskatchewan
The Canadian Light Source (CLS) synchrotron operates with four in-vacuum insertion devices, three in-vacuum undulators, and one in-vacuum wiggler. Presently, each of the devices occupies half of a straight section. The wiggler is unique in our ring as it is both in-vacuum and shares a straight section with an in-vacuum undulator. We have observed gap dependent beam instabilities in the undulator located in the straight section. In order to better understand the problem, the cause of the instabilities was investigated using 3D electromagnetic modelling. First, the ’trapped’ RF modes (natural resonances) for this undulator chamber, their Q value, and their peak frequencies were analysed using Eigenmode simulation. Secondly, beam excitation of the Eigenmodes was simulated with the Wakefield solver. Herein we present the results of this electromagnetic modelling.

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reference for this paper ※ https://doi.org/10.18429/JACoW-IPAC2019-MOPGW128

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paper received ※ 14 May 2019 paper accepted ※ 23 May 2019 issue date ※ 21 June 2019

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MOPMP008

Electron Driven Positron Source for International Linear Collider

positron, beam-loading, linac, cavity

439

M. Kuriki, T. Okugi, T. Omori, M. Satoh, Y. Seimiya, J. Urakawa, K. Yokoya
KEK, Ibaraki, Japan
H. Nagoshi
HU/AdSM, Higashi-Hiroshima, Japan
K. Negishi
Iwate University, Morioka, Iwate, Japan
Y. Sumitomo
LEBRA, Funabashi, Japan
T. Takahashi
Hiroshima University, Graduate School of Science, Higashi-Hiroshima, Japan

Funding: This work is partly supported by Japan-US Cooperative grant for scientific studies, Grant aid for scientific study by MEXT Japan (KAKENHI)
To linear colliders, huge amount of positron has to be provided comparing to ring colliders, because the beam is dumped after the collision. Electron Driven ILC Positron source has been designed as a technical backup of the undulator position source including the beam loading effect, etc. The design of the detail will be presented. To linear colliders, huge amount of positron has to be provided comparing to ring colliders, because the beam is dumped after the collision. Electron Driven ILC Positron source has been designed as a technical backup of the undulator position source including the beam loading effect, etc. The design of the detail will be presented.

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reference for this paper ※ https://doi.org/10.18429/JACoW-IPAC2019-MOPMP008

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paper received ※ 13 May 2019 paper accepted ※ 20 May 2019 issue date ※ 21 June 2019

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MOPMP009

Effect of Initial Parameters on the Super Flat Beam Generation with the Phase-Space Rotation for Linear Colliders

emittance, gun, collider, solenoid

442

M. Kuriki, R. Tamura
HU/AdSM, Higashi-Hiroshima, Japan
H. Hayano, X.J. Jin, T. Konomi, Y. Seimiya, N. Yamamoto
KEK, Ibaraki, Japan
S. Kashiwagi
Tohoku University, Research Center for Electron Photon Science, Sendai, Japan
P. Piot
Northern Illinois University, DeKalb, Illinois, USA
J.G. Power
ANL, Argonne, Illinois, USA
K. Sakaue
The University of Tokyo, The School of Engineering, Tokyo, Japan
M. Washio
RISE, Tokyo, Japan

Funding: This work is partly supported by Japan-US Cooperative grant for scientific studies, Grant aid for scientific study by MEXT Japan (KAKENHI) Kiban B.
Linear collider is a concept to realize e⁺e⁻ collision beyond the limitation of the ring colliders by the synchrotron radiation. To obtain an enough luminosity, eg. 1.0·10⁺³⁴ cm^-2sec^-1, the beam is focused down to nano-meter size with a high aspect ratio. This super flat beam is useful to improve the luminosity and to compensate the beam-beam effect, eg. Beamstrahlung. In a conventional design, the super-flat beam is produced by radiation damping in a storage ring. We propose to produce this super-flat beam with phase-space rotation techniques. We employ both Round to Flat Beam Transformation and Transverse to Longitudinal Emittance eXchange, the super flat beam can be generated by controlling the space-charge effect which spoiled the performance. We present the RFBT performance with respect to the initial conditions, i.e. beam size, initial emittance, solenoid field (strength and profile), etc.

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reference for this paper ※ https://doi.org/10.18429/JACoW-IPAC2019-MOPMP009

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paper received ※ 13 May 2019 paper accepted ※ 20 May 2019 issue date ※ 21 June 2019

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MOPMP033

LHC Run 2 Optics Commissioning Experience in View of HL-LHC

optics, luminosity, coupling, experiment

508

R. Tomás, F.S. Carlier, J.M. Coello de Portugal, J. Dilly, S.D. Fartoukh, E. Fol, D. Gamba, A. Garcia-Tabares, M. Giovannozzi, M. Hofer, E.H. Maclean, L. Malina, T.H.B. Persson, P.K. Skowroński, M. Solfaroli, M.L. Spitznagel, A. Wegscheider, J. Wenninger, D.W. Wolf
CERN, Geneva, Switzerland

LHC Run 2 has achieved a beta lower than a factor 2 below design. This has significantly challenged optics measurement and correction techniques in the linear and non-linear regimes, leading to the development of new approaches. Furthermore, experimenting with a large variety of optics has allowed facing the difficulties of future optics and gaining understanding of the machine imperfections. A summary of these aspects is given in view of their implications for the HL-LHC Project.

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reference for this paper ※ https://doi.org/10.18429/JACoW-IPAC2019-MOPMP033

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paper received ※ 07 May 2019 paper accepted ※ 20 May 2019 issue date ※ 21 June 2019

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MOPMP038

Investigation of CLIC 380 GeV Post-Collision Line

site, dipole, collider, linear-collider

528

R.M. Bodenstein, A. Abramov, S.T. Boogert, P. Burrows, L.J. Nevay
JAI, Oxford, United Kingdom
D. Schulte, R. Tomás
CERN, Meyrin, Switzerland

It has been proposed that the Compact Linear Collider (CLIC) be commissioned in stages, starting with a lower-energy, 380 GeV version for the first stage, and concluding with a 3 TeV version for the final stage. In the Conceptual Design Report (CDR) published in 2012, the post-collision line is described for the 3 TeV and 500 GeV stages. However, the post-collision line for the 380 GeV design was not investigated. This work will describe the simulation studies performed in BDSIM for the 380 GeV post-collision line.

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reference for this paper ※ https://doi.org/10.18429/JACoW-IPAC2019-MOPMP038

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paper received ※ 13 May 2019 paper accepted ※ 18 May 2019 issue date ※ 21 June 2019

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MOPMP052

Numerical Simulations of the DC Wire Prototypes in LHC for Enhancing the HL-LHC Performances

experiment, luminosity, optics, resonance

566

A. Poyet
Université Grenoble Alpes, Grenoble, France
S.D. Fartoukh, N. Karastathis, Y. Papaphilippou, K. Skoufaris, G. Sterbini
CERN, Geneva, Switzerland

For the last 15 years, the compensation of the Beam-Beam Long-Range (BBLR) interaction in colliders using DC wires has been studied. In 2015, in the frame of the HL-LHC project, it has been shown that a compensation of all the Resonance Driving Terms (RDTs) generated by the BBLR interaction is possible using wires with constraints on their transverse and longitudinal positions. In 2017, an experimental campaign has been launched in the present LHC, with wires installed in sub-optimal positions due to integration constraints. The aim of this paper is therefore to apply the formalism developped for HL-LHC to the LHC case and to compare the experimental results to the numerical tracking studies of the compensation using wires.

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reference for this paper ※ https://doi.org/10.18429/JACoW-IPAC2019-MOPMP052

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paper received ※ 06 May 2019 paper accepted ※ 20 May 2019 issue date ※ 21 June 2019

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MOPMP053

Numerical Optimization of DC Wire Compensation in HL-LHC

operation, collider, luminosity, hadron

570

K. Skoufaris, S.D. Fartoukh, N. Karastathis, Y. Papaphilippou, D. Pellegrini, A. Poyet, A. Rossi, G. Sterbini
CERN, Meyrin, Switzerland

The electromagnetic field generated from a set of DC wires parallel to the beam opens the path to the compensation of the beam-beam long-range (BBLR) interactions for the future operation of large hadron colliders, in particular for the upcoming High Luminosity upgrade of the Large Hadron Collider (HL-LHC). The effectiveness and simplicity of a current carrying wire are critical for overcoming some technical constraints of the machine. In order to better understand the potential of this device for the HL-LHC, various simulation studies are presented. The different observables are the dynamic aperture and the frequency analysis.

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reference for this paper ※ https://doi.org/10.18429/JACoW-IPAC2019-MOPMP053

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paper received ※ 03 May 2019 paper accepted ※ 20 May 2019 issue date ※ 21 June 2019

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MOPRB011

Progress on Muon Ionization Cooling Demonstration with MICE

emittance, experiment, detector, framework

594

C. Hunt
Imperial College of Science and Technology, Department of Physics, London, United Kingdom
V.C. Palladino
INFN-Napoli, Napoli, Italy
C.G. Whyte
USTRAT/SUPA, Glasgow, United Kingdom

Funding: STFC, NSF, DOE, INFN, CHIPP andd more
The Muon Ionization Cooling Experiment (MICE) at RAL has collected extensive data to study the ionization cooling of muons. Several million individual particle tracks have been recorded passing through a series of focusing magnets in a number of different configurations and a liquid hydrogen or lithium hydride absorber. Measurement of the tracks upstream and downstream of the absorber has shown the expected effects of the 4D emittance reduction. Further studies are providing now more and deeper insight.
Submitted by the chair of our MICE speakers bureau.
If accepted, a member of the collaboration will soon be identified to present the contribution and will register immediately after.

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reference for this paper ※ https://doi.org/10.18429/JACoW-IPAC2019-MOPRB011

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paper received ※ 15 May 2019 paper accepted ※ 23 May 2019 issue date ※ 21 June 2019

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MOPRB033

Preliminary Research of HOM for 100MHz Superconducting Cavity in the Pre-Research Project of HALS

HOM, cavity, impedance, damping

649

Y.G. Tang, L. Wang, C.-F. Wu
USTC/NSRL, Hefei, Anhui, People’s Republic of China

A 100MHz QWR superconducting cavity is researched in the pre-research project of Hefei Advanced Light Source (HALS). Higher order modes (HOM) damping is a big challenge for synchrotron radiation light source. In this paper, we first apply the novel choke mode structure to the 100MHz QWR (quarter wave resonator) cavity in order to damp the HOM. We identify the main harmful higher order modes. The HOMs in the QWR cavity are suppressed by optimizing the choke dimensions. The broadband HOM impedance spectrum of the cavity was also evaluated by calculating the beam induced wake potential in time domain. The results show that choke mode structure has a good HOM damping effect on the QWR cavity.

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reference for this paper ※ https://doi.org/10.18429/JACoW-IPAC2019-MOPRB033

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paper received ※ 25 April 2019 paper accepted ※ 20 May 2019 issue date ※ 21 June 2019

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MOPRB046

Status of the ESSnuSB Accumulator Design

linac, space-charge, injection, target

666

Y. Zou, T.J.C. Ekelöf, M. Olvegård, R.J.M.Y. Ruber
Uppsala University, Uppsala, Sweden
E. Bouquerel, M. Dracos
IPHC, Strasbourg Cedex 2, France
M. Eshraqi, B. Gålnander
ESS, Lund, Sweden
H.O. Schönauer, E.H.M. Wildner
CERN, Geneva, Switzerland

Funding: This project is supported by the COST Action CA15139 EuroNuNet. It has received funding from the European Union’s Horizon 2020 research and innovation programme under grant agreement No 777419.
The 2.0 GeV, 5 MW proton linac for the European Spallation Source, ESS, will have the capacity to accelerate additional pulses and send them to a neutrino target, providing an excellent opportunity to produce an unprecedented high performance neutrino beam, the ESS neutrino Super Beam, ESSnuSB, to measure, with precision, the CP violating phase at the 2nd oscillation maximum. In order to comply with the acceptance of the target and horn systems that will form the neutrino super beam, the long pulses from the linac must be compressed by about three orders of magnitude with minimal particle loss, something that will be achieved through multi-turn charge-exchange injection in an accumulator ring. This ring will accommodate over 2·10¹⁴ protons, which means that several design challenges are encountered. Strong space charge forces, low-loss injection with phase space painting, efficient collimation, a reliable charge stripping system, and e-p instabilities are some of the important aspects central to the design work. This paper presents the status of the accumulator ring design, with multi-particle simulations of the injections procedure.

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reference for this paper ※ https://doi.org/10.18429/JACoW-IPAC2019-MOPRB046

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paper received ※ 14 May 2019 paper accepted ※ 20 May 2019 issue date ※ 21 June 2019

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MOPRB048

Collimation System Studies for the FCC-hh

collimation, proton, collider, hadron

669

R. Bruce, A. Abramov, A. Bertarelli, M.I. Besana, F. Carra, F. Cerutti, M. Fiascaris, G. Gobbi, A.M. Krainer, A. Lechner, A. Mereghetti, D. Mirarchi, J. Molson, M. Pasquali, S. Redaelli, D. Schulte, E. Skordis, M. Varasteh Anvar
CERN, Geneva, Switzerland
A. Abramov
JAI, Egham, Surrey, United Kingdom
A. Faus-Golfe
LAL, Orsay, France
M. Serluca
IN2P3-LAPP, Annecy-le-Vieux, France

The Future Circular Collider (FCC-hh) is being designed as a 100 km ring that should collide 50 TeV proton beams. At 8.3 GJ, its stored beam energy will be a factor 28 higher than what has been achieved in the Large Hadron Collider, which has the highest stored beam energy among the colliders built so far. This puts unprecedented demands on the control of beam losses and collimation, since even a tiny beam loss risks quenching superconducting magnets. We present in this article the design of the FCC-hh collimation system and study the beam cleaning through simulations of tracking, energy deposition, and thermo-mechanical response. We investigate the collimation performance for design beam loss scenarios and potential bottlenecks are highlighted.

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reference for this paper ※ https://doi.org/10.18429/JACoW-IPAC2019-MOPRB048

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paper received ※ 18 April 2019 paper accepted ※ 20 May 2019 issue date ※ 21 June 2019

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MOPRB049

Study of Beam-Gas Interactions at the LHC for the Physics Beyond Colliders Fixed-Target Study

target, proton, collider, experiment

673

C. Boscolo Meneguolo, R. Bruce, F. Cerutti, M. Ferro-Luzzi, M. Giovannozzi, A. Mereghetti, J. Molson, S. Redaelli
CERN, Geneva, Switzerland
A. Abramov
JAI, Egham, Surrey, United Kingdom

Among several working groups formed in the framework of Physics Beyond Colliders study, launched at CERN in September 2016, there is one investigating specific fixed-target experiment proposals. Of particular interest is the study of high-density unpolarized or polarized gas target to be installed in the LHCb detector, using storage cells to enhance the target density. This work studies the impact of the interactions of 7 TeV proton beams with such gas targets on the LHC machine in terms of particle losses.

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reference for this paper ※ https://doi.org/10.18429/JACoW-IPAC2019-MOPRB049

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paper received ※ 17 April 2019 paper accepted ※ 19 May 2019 issue date ※ 21 June 2019

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MOPRB050

Performance of the Collimation System During the 2018 Lead Ion Run at the Large Hadron Collider

collimation, heavy-ion, proton, hadron

677

N. Fuster-Martínez, R. Bruce, J.M. Jowett, A. Mereghetti, D. Mirarchi, S. Redaelli
CERN, Meyrin, Switzerland

As part of the Large Hadron Collider (LHC) heavy-ion research programme, the last month of the 2018 LHC run was dedicated to Pb ion physics. Several heavy-ion runs have been performed since the start-up of the LHC. These runs are challenging for collimation, despite lower intensities, because of the degraded cleaning observed compared to protons. This is due to the differences of the interaction mechanisms in the collimators. Ions experience fragmentation and electromagnetic dissociation that result in a substantial flux of off-rigidity particles that escape the collimation system. In this paper, the collimation system performance and the experience gained during the 2018 Pb ion run are presented. The measured performance is compared with the expectation from the Sixtrack-FLUKA coupling simulations and the agreement discussed.

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reference for this paper ※ https://doi.org/10.18429/JACoW-IPAC2019-MOPRB050

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paper received ※ 07 May 2019 paper accepted ※ 19 May 2019 issue date ※ 21 June 2019

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MOPRB057

An Approach to Alleviating Heavy Beam Loading Effect on the Synchrotron Machine Through the Existed Low Level RF Feedback System

cavity, feedback, beam-loading, impedance

697

L.-H. Chang, F.Y. Chang, M.H. Chang, S.W. Chang, L.J. Chen, F.-T. Chung, Y.T. Li, M.-C. Lin, Z.K. Liu, C.H. Lo, Ch. Wang, M.-S. Yeh, T.-C. Yu
NSRRC, Hsinchu, Taiwan

To pursue the highest brightness and intensity of the synchrotron light, the synchrotron machines are pushed to operate with as high as possible of the beam current. To suppress the heavy beam loading effects, the direct RF feedback is currently widely used. This paper provides an another approach to alleviating the heavy beam loading effects on machine operation. Different from the direct RF feedback technique, this approach need not add additional feedback loop to the existed RF feedback system. Applying a proper angle rotation to the I-Q error signals of the cavity voltage, before entering the existed feedback loop, is the only action required in this approach. The paper will explain the working mechanism and investigate the behaviour of this approach, through an example case, with numerical simulation.

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reference for this paper ※ https://doi.org/10.18429/JACoW-IPAC2019-MOPRB057

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paper received ※ 16 April 2019 paper accepted ※ 18 May 2019 issue date ※ 21 June 2019

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MOPRB058

Collimation of Partially Stripped Ion Beams in the LHC

collimation, operation, collider, hadron

700

A. Abramov, L.J. Nevay
JAI, Egham, Surrey, United Kingdom
R. Bruce, N. Fuster-Martínez, A.A. Gorzawski, M.W. Krasny, J. Molson, S. Redaelli, M. Schaumann
CERN, Meyrin, Switzerland

In the scope of the Physics Beyond Colliders studies, the Gamma Factory initiative proposes the use of partially stripped ions as a driver of a new type, high intensity photon source in CERN’s Large Hadron Collider (LHC). In 2018, the LHC accelerated and stored partially stripped 208-Pb-81+ ions for the first time. The collimation system efficiency recorded during this test was found to be prohibitively low. The worst losses were localised in the dispersion suppressor (DS) of the betatron-cleaning insertion. Analytic arguments and simulations show that the large losses are driven by the stripping of the remaining electron from the Pb nucleus by the primary collimators. The rising dispersion in the DS pushes the resulting off-rigidity, fully-stripped ions into the aperture of the superconducting magnets. In this study the measured loss maps are compared against results from simulations. Different mitigation strategies are outlined, including a dispersion suppressor (DS) collimator, crystal collimation or an orbit bump.

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reference for this paper ※ https://doi.org/10.18429/JACoW-IPAC2019-MOPRB058

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paper received ※ 10 May 2019 paper accepted ※ 20 May 2019 issue date ※ 21 June 2019

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MOPRB059

Collimation of Heavy-Ion Beams in the HE-LHC

collimation, collider, proton, hadron

704

A. Abramov, L.J. Nevay
JAI, Egham, Surrey, United Kingdom
R. Bruce, M.P. Crouch, N. Fuster-Martínez, A. Mereghetti, J. Molson, S. Redaelli
CERN, Meyrin, Switzerland

A design study for a future collider to be built in the LHC tunnel, the High-Energy Large Hadron Collider (HE-LHC), has been launched as part of the Future Circular Collider (FCC) study at CERN. It would provide proton collisions at a centre-of-mass energy of 27 TeV as well as collisions of heavy ions at the equivalent magnetic rigidity. HE-LHC is being designed under the stringent constraint of using the existing tunnel and therefore the resulting lattice and optics differ in layout and phase advance from the LHC. It is necessary to evaluate the performance of the collimation system for ion beams in HE-LHC in addition to proton beams. In the case of ion beams, the fragmentation and electromagnetic dissociation that relativistic heavy ions can undergo in collimators, as well as the unprecedented energy per nucleon of the HE-LHC, requires dedicated simulations. Results from a study of collimation efficiency for the nominal lead ion (Pb-82-208) beams performed with the SixTrack-FLUKA coupling framework are presented. These include loss maps with comparison against an estimated quench limit as well as detailed considerations of loss spikes in the superconducting aperture for critical sections of the machine such as the dispersion suppressors.

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reference for this paper ※ https://doi.org/10.18429/JACoW-IPAC2019-MOPRB059

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paper received ※ 18 April 2019 paper accepted ※ 23 May 2019 issue date ※ 21 June 2019

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MOPRB060

Simulating Novel Collimation Schemes for High-Luminosity LHC With Merlin++

proton, scattering, collimation, electron

708

S.C. Tygier, R.B. Appleby
UMAN, Manchester, United Kingdom
R.J. Barlow, S. Rowan
IIAA, Huddersfield, United Kingdom

Due to the large stored beam energy in the HL-LHC new collimation technologies must be used to protect the machine. Active halo control of the proton beam halo with a Hollow Electron Lens can give a kick to protons at the edge of the beam without effecting the core. Various modes of operation are possible for example the electron lens can have a continuous current or it can be pulsed to different amplitudes for each passage of the proton beam. In this article we use Merlin++ simulations to show the performance of these modes for HL-LHC parameters. We also present recent simulations comparing scattering models in Merlin++.

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reference for this paper ※ https://doi.org/10.18429/JACoW-IPAC2019-MOPRB060

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paper received ※ 08 May 2019 paper accepted ※ 20 May 2019 issue date ※ 21 June 2019

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MOPRB061

Simulations and Measurements of Coherent Synchrotron Radiation at the MAX-IV Short Pulse Facility

radiation, detector, electron, dipole

712

B.S. Kyle
University of Manchester, Manchester, United Kingdom
R.B. Appleby
UMAN, Manchester, United Kingdom
M. Brandin, E. Mansten, S. Thorin
MAX IV Laboratory, Lund University, Lund, Sweden
T.H. Pacey
STFC/DL/ASTeC, Daresbury, Warrington, Cheshire, United Kingdom
P.H. Williams
Cockcroft Institute, Warrington, Cheshire, United Kingdom
J. Wolfenden
The University of Liverpool, Liverpool, United Kingdom

The Coherent Synchrotron Radiation (CSR) interaction is a source of unwanted correlated energy spread in short-bunch Free-Electron Lasers (FEL), diluting the desired FEL spectrum and reducing the total brightness of the light source. Many accelerator codes make use of 1-dimensional approximations in the calculation of the CSR-wake, which breaks down for bunch dimensions typical within bunch compressor dipoles in FELs. General Particle Tracer simulations of the CSR interaction make use of the 3-dimensional bunch distribution, making it advantageous in modelling the short-bunch, high aspect ratio regimes typical of modern 4th-generation light sources. Measurements of THz CSR emitted from the final bunch compressor dipole of the SP02 beamline at the MAX-IV Short Pulse Facility (SPF) were used, alongside start-to-end GPT and Elegant simulations, to characterize coherent radiation emission across a broad range of bunch lengths.

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reference for this paper ※ https://doi.org/10.18429/JACoW-IPAC2019-MOPRB061

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paper received ※ 14 May 2019 paper accepted ※ 20 May 2019 issue date ※ 21 June 2019

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MOPRB064

Precision Modelling of Energy Deposition in the LHC using BDSIM

proton, detector, collimation, beam-losses

723

S.D. Walker, A. Abramov, S.T. Boogert, S.M. Gibson, L.J. Nevay, H. Pikhartova
JAI, Egham, Surrey, United Kingdom

A detailed model of the Large Hadron Collider (LHC) has been built using Beam Delivery Simulation (BDSIM) for studying beam loss patterns and is presented and discussed in this paper. BDSIM is a program which builds a Geant4 accelerator model from generic components bridging accelerator tracking routines and particle physics to seamlessly simulate the traversal of particles and any subsequent energy deposition in particle accelerators. The LHC model described here has been further refined with additional features to improve the accuracy of the model, including specific component geometries, tunnel geometry, and more. BDSIM has been extended so that more meaningful comparisons with other simulations and data can be made. Firstly, BDSIM can now record losses in the same way that SixTrack does: when a primary exceeds the limits of the aperture it is recorded as a loss. Secondly, by placing beam loss monitors (BLMs) within the BDSIM model and recording the simulated dose and energy deposition, it can be directly compared with real BLM data. These results are presented here and compared with SixTrack and BLM data from a typical fill in 2018.

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reference for this paper ※ https://doi.org/10.18429/JACoW-IPAC2019-MOPRB064

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paper received ※ 15 May 2019 paper accepted ※ 20 May 2019 issue date ※ 21 June 2019

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MOPRB069

Generation of High Power Short Rf Pulses using an X-Band Metallic Power Extractor Driven by High Charge Multi-Bunch Train

pick-up, experiment, multipactoring, acceleration

734

J.H. Shao, M.E. Conde, D.S. Doran, G. Ha, W. Liu, J.G. Power, C. Whiteford, E.E. Wisniewski
ANL, Argonne, Illinois, USA
H.B. Chen, M.M. Peng, J. Shi, H. Zha
TUB, Beijing, People’s Republic of China
C.-J. Jing
Euclid TechLabs, LLC, Solon, Ohio, USA
J. Seok
UNIST, Ulsan, Republic of Korea

Short pulse two-beam acceleration (TBA) is a structure wakefield acceleration (SWFA) approach aiming to achieve gradient above 250 MV/m using rf pulses less than 20 ns. An X-band 11.7 GHz metallic power extractor has been developed as the power source to test accelerating structures in this extreme regime. The power extractor is designed to be driven by high charge bunches separated by 769.2 ps (9 times the X-band period) on an L-band 1.3 GHz beamline. In the recent experiment, ~280 MW rf pulses with 3 ns flat-top have been measured by a coaxial rf pickup when driven by 8-bunch trains with a total charge of ~500 nC. The power level is ~50% lower than the theoretical prediction and simulation. Experimental investigation suggests that the missing power was mainly caused by the multipacting issue inside the rf pickup, which could be eliminated by a newly-designed directional coupler.

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reference for this paper ※ https://doi.org/10.18429/JACoW-IPAC2019-MOPRB069

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paper received ※ 19 May 2019 paper accepted ※ 20 May 2019 issue date ※ 21 June 2019

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MOPRB081

Electron Beam’s Closed Orbit in the Crab Crossing Scheme of Future Electron-Ion Colliders

electron, closed-orbit, luminosity, cavity

762

Y. Hao, V. Ptitsyn
BNL, Upton, Long Island, New York, USA
J. Qiang
LBNL, Berkeley, California, USA

In crab-crossing collision geometry the closed orbit of the electron beam will be altered by the beam-beam interaction and the tilted head and tail of the ion beam. We will present the linear model to determine the closed orbit and compare with the simulation. Also, the relation of the closed orbit and the synchro-betatron resonance will be presented.

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reference for this paper ※ https://doi.org/10.18429/JACoW-IPAC2019-MOPRB081

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paper received ※ 15 May 2019 paper accepted ※ 20 May 2019 issue date ※ 21 June 2019

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MOPRB082

Scaling Properties of the Synchro-Beta Resonance in Crab Crossing Scheme of Future Electron Ion Collider

luminosity, resonance, electron, cavity

766

Y. Hao, Y. Luo, V. Ptitsyn
BNL, Upton, Long Island, New York, USA
J. Qiang
LBNL, Berkeley, California, USA

The synchro - beta resonance due to the beam-beam interaction was predicted by the strong-strong simulation in the future electron-ion collider designs. In this paper, we study the scaling properties of the degradation rate of this unwanted resonance. These studies motivated the possible countermeasures of the luminosity degradation associated with the resonance.

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reference for this paper ※ https://doi.org/10.18429/JACoW-IPAC2019-MOPRB082

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paper received ※ 15 May 2019 paper accepted ※ 20 May 2019 issue date ※ 21 June 2019

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MOPRB090

Simulation Challenges for eRHIC Beam-Beam Study

electron, proton, damping, emittance

785

Y. Luo, F.J. Willeke
BNL, Upton, Long Island, New York, USA
Y. Hao
FRIB, East Lansing, Michigan, USA
J. Qiang
LBNL, Berkeley, California, USA
Y. Roblin, H. Zhang
JLab, Newport News, Virginia, USA

Funding: Work supported by Brookhaven Science Associates, LLC under Contract No. DE-AC02-98CH10886 with the U.S. Department of Energy.
The 2015 Nuclear Science Advisory Committee Long Rang Plan identified the need for an electron-ion collider (EIC) facility as a gluon microscope with capabilities beyond those of any existing accelerator complex. To reach the required high energy, high luminosity, and high polarization, the eRHIC design, based on the existing heavy ion and polarized proton collider RHIC, adopts a very small \beta-function at the interaction points, a high collision repetition rate, and a novel hadron cooling scheme. A full crossing angle of 22 mrad and crab cavities for both electron and proton rings are required. In this article, we will present the high priority R\&D items related to the beam-beam interaction studies for the current eRHIC design, the simulation challenges, and our plans and methods to address them. Recent progresses on this project are reported too.

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reference for this paper ※ https://doi.org/10.18429/JACoW-IPAC2019-MOPRB090

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paper received ※ 14 May 2019 paper accepted ※ 20 May 2019 issue date ※ 21 June 2019

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MOPRB091

Combined Strong-Strong and Weak-Strong Beam-Beam Simulations for Crabbed Collision in eRHIC

electron, proton, luminosity, cavity

788

Y. Luo, G. Bassi, M. Blaskiewicz, W. Fischer, Y. Hao, C. Montag, V. Ptitsyn, V.V. Smaluk, F.J. Willeke
BNL, Upton, Long Island, New York, USA
K. Ohmi
KEK, Ibaraki, Japan
J. Qiang
LBNL, Berkeley, California, USA

Funding: Work supported by Brookhaven Science Associates, LLC under Contract No. DE-AC02-98CH10886 with the U.S. Department of Energy.
In the eRHIC, to compensate the geometric luminosity loss, local crab cavities on both sides of the interaction points are to adopted. The previous strong-strong beam-beam simulations showed that the luminosity degradation depends on the crab cavity frequency, proton synchrotron tune, proton bunch length and so on. In this article, we apply a combined strong-strong and weak-strong beam-beam simulation to investigate the incoherent and coherent beam motions with crabbed collison, and to calculate more realistic beam emittance growth rates and luminosity degradation rate.

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reference for this paper ※ https://doi.org/10.18429/JACoW-IPAC2019-MOPRB091

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paper received ※ 14 May 2019 paper accepted ※ 20 May 2019 issue date ※ 21 June 2019

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MOPRB092

Symplectic and Exact Tracking of Low Energy 197Au⁷⁸⁺ in the Relativistic Heavy Ion Collider

electron, quadrupole, storage-ring, lattice

791

Y. Luo, W. Fischer, F. Méot, G. Robert-Demolaize
BNL, Upton, Long Island, New York, USA

Funding: Work supported by Brookhaven Science Associates, LLC under Contract No. DE-AC02-98CH10886 with the U.S. Department of Energy.
In the coming RHIC low energy scan, the electron cooling technique is to be used to cool the ions 197Au⁷⁹⁺ with its energy range between 3.85~GeV/nucleon to 5.75~GeV/nucleon. To overlap the electron beam and the 197Au⁷⁹⁺ beam at the cooling section, a recombination monitor is to be used to detect the maximum flux of 197Au⁷⁸⁺ ions generated in the cooling section. In the previous studies, we tracked 197Au⁷⁸⁺ ions through the RHIC lattice defined with 197Au⁷⁹⁺ with an equivalent momentum deviation. In the article, we explode different symplectic ways to track 197Au⁷⁸⁺ ions exactly. We calculate and compare the trajectories and loss map of 197Au⁷⁸⁺ ions through the RHIC ring.

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reference for this paper ※ https://doi.org/10.18429/JACoW-IPAC2019-MOPRB092

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paper received ※ 14 May 2019 paper accepted ※ 20 May 2019 issue date ※ 21 June 2019

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MOPRB104

A Parameter Study for Improving the Performance of the Production Target for the Fermilab Muon g-2 Experiment

target, experiment, storage-ring, proton

806

D. Stratakis
Fermilab, Batavia, Illinois, USA

The target station of the Muon g-2 Experiment is one of the central pieces for the production of secondary pions which eventually will decay to the desired mu-ons. In this paper, we report adjustments made to opti-mize its performance. For instance, in the simulation we vary the size of the primary incoming beam and examine its impact on the downstream production. We then compare this with the actual measured beam size upstream of the target. In addition, we examine the sensitivity in performance with the strength of the lithium lens for pion capture and the distance between lens and target. We compare measured data with simu-lation results.

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reference for this paper ※ https://doi.org/10.18429/JACoW-IPAC2019-MOPRB104

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paper received ※ 13 May 2019 paper accepted ※ 20 May 2019 issue date ※ 21 June 2019

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MOPRB105

Measurement and Analysis of Beam Phase-space Distributions for the Fermilab Muon Campus accelerator complex

quadrupole, emittance, framework, experiment

810

A. Ramirez
University of Houston, Houston, Texas, USA
D. Stratakis
Fermilab, Batavia, Illinois, USA

The Muon g-2 experiment at Fermilab is tasked with measuring the muon’s anomalous magnetic moment with high precision. Since the experiment requires large amounts of muons, it is imperative to systematically study the behavior of the beam along the transport line. Unfortunately, the available diagnostics only provide beam information in X-Y space. For a complete evaluation, information of the phase-space is required. This paper demonstrates a technique to measure the beam phase-space distribution by using a set of beam profiles. First, we establish the theoretical framework that describes the principle of the technique. Next, we apply the technique at four different locations along the accelerator delivery line. Finally, we compare our findings to predictions from tracking simulations. Our results indicate that the beam phase-space volume is conserved, along the beam delivery line, suggesting minimal loses and linear transport as expected by design. Compared to the simulations, there is good agreement in both horizontal and vertical plane with the former being at the 4% level while the latter being in the 15% level. Our proposed technique is expected to provide a promising approach for optimizing injection and thereby improving the performance of the Muon g-2 Experiment.

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reference for this paper ※ https://doi.org/10.18429/JACoW-IPAC2019-MOPRB105

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paper received ※ 13 May 2019 paper accepted ※ 20 May 2019 issue date ※ 21 June 2019

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MOPRB106

3D Theory of Microbunched Electron Cooling for Electron-Ion Colliders

electron, hadron, kicker, betatron

814

G. Stupakov, P. Baxevanis
SLAC, Menlo Park, California, USA

Funding: This work was supported by the Department of Energy, Contract No. DE-AC02-76SF00515.
The Microbunched Electron Cooling (MBEC) * is a promising cooling technique that can find applications in future hadron and electron-ion colliders. A 1D model of MBEC has been recently developed in Ref. **. This model predicts the cooling time below two hours for eRHIC 255 GeV proton beams, when two amplification sections are used in the cooling system. In this work, we go beyond the 1D model of Ref. * and develop a realistic 3D theory of MBEC. Our approach is based on the analysis of the dynamics of microscopic 3D fluctuations in the electron and hadron beams during their interaction and propagation through the system. We derive an analytical expression for the cooling rate and optimize it for the parameters of eRHIC. Our analytical results are in reasonable agreement with simulations.
* D. Ratner. Phys. Rev. Lett. 111, 084802 (2013).
** G. Stupakov. PRAB 21, 114402 (2018)

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reference for this paper ※ https://doi.org/10.18429/JACoW-IPAC2019-MOPRB106

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paper received ※ 29 April 2019 paper accepted ※ 18 May 2019 issue date ※ 21 June 2019

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MOPRB116

Laser Sculpted Cool Proton Beams

laser, emittance, linac, proton

826

S.M. Gibson, L.J. Nevay
Royal Holloway, University of London, Surrey, United Kingdom
S.E. Alden, S.M. Gibson, L.J. Nevay
JAI, Egham, Surrey, United Kingdom

Funding: We acknowledge support by STFC grant ST/P003028/1
Hydrogen ion accelerators, such as CERN’s Linac4, are increasingly used as the front end of high power proton drivers for high energy physics, spallation neutron sources and other applications. Typically, a foil strips the hydrogen ion beam to facilitate charge-exchange injection of protons into orbits of high energy accelerators, in which the resulting emittance is dominated by phase-space painting. In this paper, a new method to laser extract a narrow beam of neutralised hydrogen from the parent H⁻ ion beam is proposed. Subsequent foil stripping and capture of protons into a storage ring generates cool proton bunches with significantly reduced emittance compared to the parent beam. The properties of the extracted proton beam can be precisely controlled and sculpted by adjusting the optical parameters of the laser beam. Recirculation of the parent beam allows time for space-charge effects to repopulate the emittance phase space prior to repeated laser extraction. We present particle tracking simulations of the proposed scheme, including the laser-particle interaction with realistic optical parameters and show the resulting emittance is reduced. Developments for an experimental demonstration of a laser controlled particle beam are outlined. In principle, the proposed scheme could considerably reduce the emittance of protons bunches injected into an accelerator, such as the LHC.

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reference for this paper ※ https://doi.org/10.18429/JACoW-IPAC2019-MOPRB116

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paper received ※ 16 May 2019 paper accepted ※ 23 May 2019 issue date ※ 21 June 2019

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MOPTS010

Simulation of the Guide Field Flipping Procedure for the Frequency Domain Method

GUI, lattice, sextupole, dipole

858

A.E. Aksentyev
FZJ, Jülich, Germany
A.E. Aksentyev
MEPhI, Moscow, Russia
A.E. Aksentyev, V. Senichev
RAS/INR, Moscow, Russia

The spin vector of a particle injected into a perfectly aligned storage ring precesses about the vertically-orientated guide field. In the presence of an Electric Dipole Moment (EDM), the spin precession axis acquires a proportional radial component. However, in an imperfect ring, rotational magnet misalignments induce a radial component to the spin precession axis, related to the Magnetic Dipole Moment (MDM). In the Frequency Domain Method, [*] this additional precession is dealt with by consecutively injecting the beam in opposite directions, and constructing the EDM estimator as the sum of the clockwise and counter-clockwise vertical plane precession frequencies. Since the radial MDM component changes sign when the magnetic field direction is reversed, it cancels in the sum, leaving only the EDM effect. In order to reproduce the guide field magnitude with precision sufficient for the cancellation of the MDM effect, we propose to calibrate the guide field via the horizontal plane precession frequency. In the present work we describe the algorithm of the field flipping procedure, and do a numerical simulation.
[*] Senichev Y, Aksentev A, Ivanov A, Valetov E. Frequency domain method of the search for the deuteron electric dipole moment in a storage ring with imperfections. arXiv:171106512. 2017 Nov 17.

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reference for this paper ※ https://doi.org/10.18429/JACoW-IPAC2019-MOPTS010

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paper received ※ 08 April 2019 paper accepted ※ 23 May 2019 issue date ※ 21 June 2019

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MOPTS012

Spin Decoherence in the Frozen Spin Storage Ring Method of Search for a Particle EDM

sextupole, storage-ring, lattice, betatron

864

A.E. Aksentyev
FZJ, Jülich, Germany
A.E. Aksentyev
MEPhI, Moscow, Russia
A.E. Aksentyev, V. Senichev
RAS/INR, Moscow, Russia

Spin coherence refers to a measure of preservation of polarization in an initially polarized beam. The spin vector of a particle injected into a storage ring starts to precess about the vertical magnetic field vector in accordance with the Thomas-BMT equation. The precession frequency is dependent on the equilibrium-level energy, which differs across the beam particles. This does not pose a problem when the initial polarization is vertical; however, the Frozen Spin Storage Ring EDM search method [*] requires beam polarization along the momentum vector, i.e., in the horizontal plane. In the present work we analyze the source of decoherence, and investigate the way it can be suppressed in the horizontal plane in a perfectly aligned ring by means of sextupole fields. We also consider the case of an imperfect ring: transference of decoherence into the vertical plane induced by vertical plane spin precession, and the effect of sextupole fields.
* D. Anastassopoulos et al. AGS Proposal: Search for a permanent electric dipole moment of the deuteron nucleus at the 10 −29 e · cm level. BNL report, 2008.

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reference for this paper ※ https://doi.org/10.18429/JACoW-IPAC2019-MOPTS012

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paper received ※ 08 April 2019 paper accepted ※ 20 May 2019 issue date ※ 21 June 2019

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MOPTS016

Compression and Noise Reduction of Field Maps

cavity, DTL, MMI, extraction

875

X. Du, L. Groening
GSI, Darmstadt, Germany

Errors from discretization and large data volume of field maps is a concern for beam dynamics simulations with respect to achievable accuracy and to the required amount of time. High-order singular value decomposition (HOSVD) has recently emerged as simple, effective, and adaptive tool to extract the essentials from multidimensional data. This paper is on the feasibility of compression and noise reduction of electromagnetic field map data with HOSVD. The method has been applied to an electric field map of a DTL cavity with 11 m in length comprising 55 rf-gaps. The original field map data of 220 MB was converted into practically noise-free data of just 20 KB. Noise was reduced by 95% as demonstrated using a cubic cavity for which the analytical field map is available.

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reference for this paper ※ https://doi.org/10.18429/JACoW-IPAC2019-MOPTS016

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paper received ※ 13 May 2019 paper accepted ※ 23 May 2019 issue date ※ 21 June 2019

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MOPTS019

End to End Simulations and Error Studies of the FAIR Proton Linac

linac, cavity, rfq, proton

885

H. Hähnel, U. Ratzinger, M. Syha, R. Tiede
IAP, Frankfurt am Main, Germany
C.M. Kleffner
GSI, Darmstadt, Germany

The FAIR proton linac is developed as the high current proton injector for the future FAIR antiproton production chain at GSI. It will provide a 70 mA proton beam at an energy of 68 MeV to the SIS18 synchrotron. The linac consists of an ECR ion source, followed by a ladder RFQ and a normalconducting linac based on CH-type cavities. High beam currents and strict beam quality requirements were the main drivers for the beam dynamics design. To ensure matching between the individual sections and validate the injector design as a whole, end to end simulations were performed using TraceWin with 3D fieldmaps of the CH-linac. In this paper, the final cavity design, as well as the results of end to end simulations and error studies are discussed.

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reference for this paper ※ https://doi.org/10.18429/JACoW-IPAC2019-MOPTS019

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paper received ※ 13 May 2019 paper accepted ※ 20 May 2019 issue date ※ 21 June 2019

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MOPTS020

Status of the FAIR Proton LINAC

proton, linac, cavity, rfq

889

C.M. Kleffner, S. Appel, R. Berezov, J. Fils, P. Forck, P. Gerhard, M. Kaiser, K. Knie, A. Krämer, C. Mühle, S. Puetz, A. Schnase, G. Schreiber, A. Seibel, T. Sieber, V. Srinivasan, J. Trüller, W. Vinzenz, M. Vossberg, C. Will
GSI, Darmstadt, Germany
H. Hähnel, U. Ratzinger, M. Schuett, M. Syha
IAP, Frankfurt am Main, Germany

For the production of Antiproton beams with sufficient intensities, a dedicated high-intensity 325 MHz Proton linac is currently under construction. The Proton linac shall deliver a beam current of up to 70 mA with an energy of 68 MeV for injection into SIS18. The source is designed for the generation of 100 mA beams. The Low-Energy Beam Transport line (LEBT) contains two magnetic solenoid lenses enclosing a diagnostics chamber, a beam chopper and a beam conus. A ladder 4-Rod RFQ and six normal conducting crossbar cavities of CCH and CH type arranged in two sections accelerate the beam to the final energy of 68 MeV. The technical design of the DTL CH cavities are presented and the commissioning measurements of the ion source are described. The construction and the procurement progress, the design and testing results of the key hardware are presented.

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reference for this paper ※ https://doi.org/10.18429/JACoW-IPAC2019-MOPTS020

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paper received ※ 14 May 2019 paper accepted ※ 23 May 2019 issue date ※ 21 June 2019

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MOPTS025

Overview of the ARES Bunch Compressor at SINBAD

electron, laser, plasma, linac

902

F. Lemery
University of Hamburg, Hamburg, Germany
R.W. Aßmann, U. Dorda, K. Flöttmann, J. Hauser, M. Hüning, G. Kube, M. Lantschner, S. Lederer, B. Marchetti, N. Mildner, M. Pelzer, M. Rosan, J. Tiessen, K. Wittenburg
DESY, Hamburg, Germany

Funding: This project has received funding from the European Unions Horizon 2020 Research and Innovation programme under Grant Agreement No 730871.
Bunch compressors are essential for the generation of short bunches with applications in e.g. colliders, free electron lasers, and advanced accelerator concepts. The up-and-coming ARES accelerator located at SINBAD, DESY will support the formation of ~100~MeV, pC, sub-fs electron bunches for LWFA research and development. We give an overview on the ARES bunch compressor, providing start-to-end simulations of the machine and an update on its technical design.

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reference for this paper ※ https://doi.org/10.18429/JACoW-IPAC2019-MOPTS025

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paper received ※ 17 May 2019 paper accepted ※ 20 May 2019 issue date ※ 21 June 2019

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MOPTS028

Search for Electric Dipole Moments at Cosy in Jülich - Spin-Tracking Simulations Using Bmad

dipole, storage-ring, experiment, alignment

914

V. Poncza, A. Lehrach
FZJ, Jülich, Germany
A. Lehrach, V. Poncza
RWTH, Aachen, Germany

The observed matter-antimatter asymmetry in the universe cannot be explained by the Standard Model (SM) of particle physics. In order to resolve the matter dominance an additional CP violating phenomenon is needed. A candidate for physics beyond the SM is a non-vanishing Electric Dipole Moment (EDM) of subatomic particles. Since permanent EDMs violate parity and time reversal symmetries, they are also CP violating if the CPT -theorem is assumed. The JEDI (Jülich Electric Dipole moment Investigations) collaboration in Jülich is preparing a direct EDM measurement of protons and deuterons first at the storage ring COSY (COoler SYnchrotron) and later at a dedicated storage ring. In order to analyse the data and to disentangle the EDM signal from systematic effects spin tracking simulations are needed. Therefore a model of COSY was implemented using the software library Bmad. It includes the measured magnet misalignments of the latest survey and a simplified description of the RF-Wien Filter device that is used for the EDM measurement. The model was successfully benchmarked using analytical predictions of the spin behavior. A crucial point regarding the data analysis is the knowledge of the orientation of the invariant spin axis with vanishing EDM at the position of the RF-Wien Filter. Especially its radial component is unknown and spin tracking simulations can be used to determine this missing number. Tracking results as well as the algorithm to find the invariant spin axis will be presented.

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reference for this paper ※ https://doi.org/10.18429/JACoW-IPAC2019-MOPTS028

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paper received ※ 25 April 2019 paper accepted ※ 20 May 2019 issue date ※ 21 June 2019

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MOPTS030

Characterisation and First Beam Line Tests of the Elbe Stripline Kicker

kicker, laser, septum, neutron

918

Ch. Schneider, A. Arnold, M. Freitag, J. Hauser, P. Michel
HZDR, Dresden, Germany

The linac based CW electron accelerator ELBE operates different secondary beamlines one at a time. For the future different end stations should be served simultaneously, hence specific bunch patterns have to be kicked into different beam-lines. The variability of the bunch pattern and the frequency resp. switching time are one of the main arguments for a stripline-kicker. A design with two tapered active electrodes and two ground fenders was optimized in time and frequency domain with the software package CST. From that a design has been transferred into a construction and was manufactured. The prototype has been tested in the laboratory and installed in the ELBE beam line. The presentation summarises the recent results and the first beam line test.

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reference for this paper ※ https://doi.org/10.18429/JACoW-IPAC2019-MOPTS030

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paper received ※ 10 May 2019 paper accepted ※ 20 May 2019 issue date ※ 21 June 2019

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MOPTS032

New Beam Dynamics Simulations for the FAIR p-Linac RFQ

rfq, linac, emittance, LEBT

921

M. Syha, H. Hähnel, U. Ratzinger, M. Schuett
IAP, Frankfurt am Main, Germany

The construction of a 3.3m Ladder-RFQ at IAP*, Goethe University Frankfurt, has been finished successfully last summer. This RFQ is designed to accelerate protons from 95 keV to 3.0 MeV according to the design parameters of the p-Linac at FAIR**. Along the acceleration section the parameters modulation, aperture and synchronous phase are varied linearly with cell number, which differs from former designs from IAP Frankfurt. The ratio of transversal vane curvature radius to mid-cell radial aperture and the vane radius itself are constant. The development of an adequate beam dynamics design was done with the aid of the RFQGen-code and in close collaboration with the IAP resonator design team. The RFQ beam dynamics design could be successfully reproduced with the TOUTATIS-routine of CEAs*** TraceWin-code. Several new beam dynamics simulations were performed on the design. Among these were current and Twiss parameter studies as well as simulations concerned with the investigation of longitudinal entrance and exit gap field effects. Others were based on new measurements in the LEBT-line performed by the GSI**** Ion Source Group in April 2019. In the near future, further LEBT measurements and subsequent simulations (among other to design a well-fitting cone for the RFQ), as well as mechanical error studies in TOUTATIS, will follow.
*Institute of Applied Physics
**Facility for Antiproton and Ion Research
***French Alternative Energies and Atomic Energy Commission
****GSI Helmholtz Centre for Heavy Ion Research

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reference for this paper ※ https://doi.org/10.18429/JACoW-IPAC2019-MOPTS032

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paper received ※ 14 May 2019 paper accepted ※ 20 May 2019 issue date ※ 21 June 2019

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MOPTS033

RF Measurements and Tuning of the 325 MHz Ladder-RFQ

rfq, linac, operation, proton

925

M. Schuett, U. Ratzinger, M. Syha
IAP, Frankfurt am Main, Germany

Funding: BMBF 05P15RFRBA
Based on the positive results of the unmodulated 325 MHz Ladder-RFQ prototype from 2013 to 2016, we developed and designed a modulated 3.4 m Ladder-RFQ*. The unmodulated Ladder-RFQ features a very constant voltage along the axis. It accepted 3 times the operating power of which is needed in operation**. That level corresponds to a Kilpatrick factor of 3.1 with a pulse length of 200 µs. The 325 MHz RFQ is designed to accelerate protons from 95 keV to 3.0 MeV according to the design parameters of the proton linac within the FAIR project. This particular high frequency for a 4-ROD-RFQ creates difficulties, which triggered the development of a Ladder-RFQ with its high symmetry. The results of the unmodulated prototype have shown, that the Ladder-RFQ is very well suited for that frequency. The duty cycle is up to 5% for the applied cooling concept. Manufacturing has been completed in September 2018. We will show the finalization of assembly after manufacturing as well as low level RF measurements. The final machining step for both flatness and frequency tuning has been finished in April 2019.
*Journal of Physics: Conf. Series 874 (2017) 012048
**Proceedings of LINAC2016, East Lansing, TUPLR053

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reference for this paper ※ https://doi.org/10.18429/JACoW-IPAC2019-MOPTS033

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paper received ※ 01 May 2019 paper accepted ※ 17 May 2019 issue date ※ 21 June 2019

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MOPTS036

RFQ Electrodes Change and Upgrade Option at the UNILAC HSI Injector

rfq, operation, cavity, MMI

936

M. Vossberg, P. Gerhard, L. Groening, S. Mickat, H. Vormann, C. Xiao
GSI, Darmstadt, Germany
V. Bencini, J.M. Garland, J.-B. Lallement, A.M. Lombardi
CERN, Geneva, Switzerland

In order to meet the beam intensity and quality requirements imposed by FAIR, the HSI-RFQ beam dynamics originally dating from 2009 has been re-designed recently at CERN. Front-to-end simulations demonstrated that the new design meets the FAIR targets. Implementation of the new electrodes, initially planned for 2019, will require re-adaption of the RFQ cavity rf-parameters by re-shaping the stems that keep the electrodes. However, during the beam time 2018 the existing RFQ did not reach its nominal voltage most likely due to expired lifetime of the electrodes originating from 2009. In order to shorten the RFQ maintenance period and to minimize any risk for upcoming beam time 2019, it was decided to post-pone the implementation of the new design and rather just re-producing the 2009 design electrodes. This contribution is on the re-production process as short-term solution and on the full implementation of the new design as mid-term solution. CST simulations performed at GSI assure that the resonance frequency with the new electrode geometry is recuperated through corrections of the carrier rings. The status of the exchange of the electrodes and simulations for the adaptation of the new electrode design are presented.

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reference for this paper ※ https://doi.org/10.18429/JACoW-IPAC2019-MOPTS036

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paper received ※ 13 May 2019 paper accepted ※ 17 May 2019 issue date ※ 21 June 2019

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MOPTS037

Comparison Between Measurement and Simulation of a Full Scale Prototype for the Proton Injector at FAIR

cavity, proton, linac, resonance

940

A. Seibel, C.M. Kleffner, K. Knie, M. Vossberg
GSI, Darmstadt, Germany
U. Ratzinger
IAP, Frankfurt am Main, Germany

A dedicated 68 MeV, 70 mA proton injector is required for the research program at FAIR (Facility for Antiproton and Ion Research). This 325 MHz linear injector contains a RFQ and six CH structures. The CH (Crossbar H-mode) structures are working in the H₂10 mode. The main acceleration of this room temperature linac will be provided by the CH structures. For the second acceleration from 11.5 MeV to 24.2 MeV a full scale prototype has been built. This structure consists of two individual CH resonators and a coupling cell. Inside the structure there are 17 tuners, they have an impact on the electric field and the frequency. For operation a flat field is required, therefore this tuners must be correctly positioned. Some series of low level tuning and frequency measurements were done to determine the size of the tuners. Low level measurements and simulations will be compared and presented.

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reference for this paper ※ https://doi.org/10.18429/JACoW-IPAC2019-MOPTS037

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paper received ※ 14 May 2019 paper accepted ※ 23 May 2019 issue date ※ 21 June 2019

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MOPTS048

Longitudinal Measurements and Beam Tuning in the J-PARC Linac MEBT1

MEBT, linac, DTL, rfq

968

M. Otani
J-PARC, KEK & JAEA, Ibaraki-ken, Japan
K. Futatsukawa, T. Miyao
KEK, Ibaraki, Japan
K. Hirano, Y. Kondo, A. Miura, H. Oguri
JAEA/J-PARC, Tokai-mura, Japan
Y. Liu
KEK/JAEA, Ibaraki-Ken, Japan

J-PARC linac is operated with design peak current of 50 mA from October 2018. Recently we succeeded in establishing longitudinal measurement at MEBT1, with which the beam matching is being studied in MEBT1. In this poster, recent measurements and beam tuning results in MEBT1 will be presented.

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reference for this paper ※ https://doi.org/10.18429/JACoW-IPAC2019-MOPTS048

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paper received ※ 30 April 2019 paper accepted ※ 20 May 2019 issue date ※ 21 June 2019

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MOPTS050

VSWR Adjustment for ACS Cavity in J-PARC LINAC

cavity, coupling, GUI, linac

974

J. Tamura, Y. Kondo, T. Morishita
JAEA/J-PARC, Tokai-mura, Japan
F. Naito, M. Otani
KEK, Tokai, Ibaraki, Japan
Y. Nemoto
Nippon Advanced Technology Co., Ltd., Tokai, Japan

In the Japan Proton Accelerator Research Complex (J-PARC) linac, negative hydrogen beams are accelerated from 190 MeV to 400 MeV by twenty-one Annular-ring Coupled Structure (ACS) accelerating cavities. The input coupler of the ACS high-beta cavity, which is the 21st accelerating cavity (ACS21) in the order of beam acceleration, had a comparatively larger value of the Voltage Standing Wave Ratio (VSWR) than those of the other ACS cavities. To adjust the VSWR of the ACS21, we designed and fabricated a rectangular waveguide with a capacitive iris which conduces to a better matching between the cavity and the waveguide. In the 2018 summer maintenance period, we installed the newly fabricated waveguide to the ACS21 in the position between the input coupler and the RF window. Consequently, the VSWR of the ACS21 was successfully decreased to the target value which leads to the critical coupling under the nominal accelerating condition with 50-mA peak beam current.

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paper received ※ 01 May 2019 paper accepted ※ 18 May 2019 issue date ※ 21 June 2019

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MOPTS052

Simulation of Electric and Thermal Behavior of Cryogenic Three-cell Copper Accelerating Cavity for High Gradient Experiments

cavity, cryogenics, coupling, experiment

980

T. Tanaka, K. Hayakawa, Y. Hayakawa, K. Nogami, T. Sakai, Y. Sumitomo, Y. Takahashi
LEBRA, Funabashi, Japan

A C-band three-cell pi-mode accelerating cavity made of high purity copper is under design for use in ultra-high accelerating gradient experiments at a cavity temperature of 20 K. The basic configuration, consisting of mode converter, short circular waveguide and cells with round periphery, is the same as that which was previously employed in the cold model for a 2.6-cell photocathode electron gun cavity. Though the 0.6-cell part in the previous model is replaced with a full cell having a beam duct, the overall electric property of the cavity will not change significantly. The RF input coupling coefficient is adjusted to around 10 at 20 K, which is expected to be lowered significantly due to the increase in the surface resistance by the rapid temperature rise during a high power RF input. The results of the simulations on the electric field and the temperature rise along the cavity surface during the RF pulse are discussed in the report.

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reference for this paper ※ https://doi.org/10.18429/JACoW-IPAC2019-MOPTS052

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paper received ※ 13 May 2019 paper accepted ※ 19 May 2019 issue date ※ 21 June 2019

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MOPTS057

SSPA upgrade plan design for CiADS

cavity, controls, coupling, klystron

990

Q. Chen, Z. Gao, Y. He, G. Huang, R. Huang, T.C. Jiang, S.H. Liu, L.P. Sun, X.W. Wang, Z.J. Wang, W.M. Yue
IMP/CAS, Lanzhou, People’s Republic of China

Funding: Supported by the National natural science foundation of China (Grand No. 11525523 and 91426303)
For ADS application, both research and commercial facilities requires extremely large amount of RF power to drive several mega watts beam power, so proper RF power upgrade plan can reduce the budget per phase and increase the valuable experience in engineering. CiADS (China initiative Accelerator Drive System) proposes to employ SSPA (Solid State Power Amplifier) as RF power source for flexible configuring and upgrading in the future. In this paper, from an engineering point of view, it is acceptable if proper matching beam current was selected for adopting fixed-coupling input coupler while only sacrificed some RF power during the upgrade plan. SSPA upgrade plan start with the stablility requirement to determine bandwidth, then combined with other RF power requirements to select output level, finally, checking how much the surplus of selected level SSPA for detuning control. The calculation and evaluation results for a §I{545}{MeV} physical design lattice illustrate that some resonance cavities had very limited surplus RF power left for detuning control that provided necessary optimization direction and guidelines for both physical design and SSPA arrangement.

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reference for this paper ※ https://doi.org/10.18429/JACoW-IPAC2019-MOPTS057

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paper received ※ 30 April 2019 paper accepted ※ 20 May 2019 issue date ※ 21 June 2019

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MOPTS072

RF DESIGN OF AN 81.25 MHz BENT-VANE TYPE RFQ

rfq, cavity, linac, ECR

1015

L. Yang, T. He, Y. He, L. Lu, C.C. Xing, L. Yang
IMP/CAS, Lanzhou, People’s Republic of China
A.H. Li
IHEP, Beijing, People’s Republic of China

The bent-vane type RFQ is proposed at IMP, Chinese Academy of Sciences, which can downsize cross section and has the simple cooling system in low frequency field. The vanes of the four-vane type RFQ are bent to form the new RFQ structure. In order to research its RF properties, the prototype cavity of an 81.25 MHZ bent-vane type RFQ is designed. This paper presents the preliminary RF design of the prototype cavity.

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reference for this paper ※ https://doi.org/10.18429/JACoW-IPAC2019-MOPTS072

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paper received ※ 17 May 2019 paper accepted ※ 20 May 2019 issue date ※ 21 June 2019

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MOPTS083

Beam Dynamics Simulation with an Updated Model for the ESS Ion Source and Low Energy Beam Transport

LEBT, rfq, solenoid, emittance

1042

E. Nilsson, M. Eshraqi, J.F. Esteban Müller, Y. Levinsen, N. Milas, R. Miyamoto
ESS, Lund, Sweden

Beam dynamics simulation of the ion source (IS) and low energy beam transport (LEBT) of the European Spallation Source (ESS) Linac is conducted with TraceWin and IBSimu code. TraceWin allows multi-particle tracking based on a particle-in-cell space-charge solver and is the standard simulation tool of the whole ESS Linac. IBSimu is based on a Vlasov solver and allows to simulate beam extraction from plasma as well as the beam transport in the LEBT. In preparation for beam commissioning of the IS and LEBT in the ESS Linac tunnel, which started in September 2018 and is ongoing as of the timing of writing this paper, the simulation models of the IS and LEBT in these two codes were updated. This paper reports the effort for these updates, including the beam distribution out of the IS, electromagnetic field map of the LEBT solenoid, more realistic aperture structure in the LEBT, as well as updated LEBT solenoids scan simulation.

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reference for this paper ※ https://doi.org/10.18429/JACoW-IPAC2019-MOPTS083

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paper received ※ 17 May 2019 paper accepted ※ 18 May 2019 issue date ※ 21 June 2019

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MOPTS095

Optimization of the Alba Linac Operation Modes

linac, gun, focusing, solenoid

1086

E. Marín, D. Lanaia, R. Muñoz Horta, F. Pérez
ALBA-CELLS Synchrotron, Cerdanyola del Vallès, Spain

ALBA is a third generation synchrotron light source that consists on a linac, booster and storage ring. The linac is capable of operating in single (SBM) and multi-bunch injection mode (MBM). Since 2016 the Single Bunch Bucket Selection algorithm which runs in SBM, permits to inject on a selected bucket keeping the charge uniformity along the ring below 4\%. However when running in SBM a significantly lower transmission along the linac is observed, with respect to the one when running in MBM. Simulation efforts have been deployed in order to build up a reliable model of the ALBA linac which can reproduce the experimental measurements. In this paper we present the new simulation model that renders the experimental observations, and the new optimization procedure developed in simulations and tested in the real machine.

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reference for this paper ※ https://doi.org/10.18429/JACoW-IPAC2019-MOPTS095

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paper received ※ 12 May 2019 paper accepted ※ 20 May 2019 issue date ※ 21 June 2019

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MOPTS096

Linac4: Reliability Run Results and Source Extraction Studies

emittance, extraction, linac, plasma

1090

D. Noll, G. Bellodi, S.B. Bertolo, F.D.L. Di Lorenzo, J.-B. Lallement, J. Lettry, A.M. Lombardi, C.M. Mastrostefano, B. Mikulec, M. O’Neil, S. Schuh, R. Wegner
CERN, Meyrin, Switzerland

Linac4, a 160 MeV, 352.2 MHz linear accelerator, has been fully commissioned and will take its place as new injector to the CERN chain of accelerators during the long shutdown (LS2) in 2019-2020. In the past year, it has been continuously providing beam during a test run to assess its reliability in view of the connection to the LHC injector chain. The target reliability of more than 90% has been demonstrated during the accumulated nine months of run in 2017 and 2018. The beam quality at 160 MeV is suitable for producing all beams for the CERN physics program of today. Nevertheless, the limited peak current of 30mA might be a limitation for future high intensity programs. The bottleneck has been identified at the low energy end of the accelerator. In the meantime, beam extraction and low energy beam transport studies are ongoing at a dedicated test stand with the goal to reach beam currents from the pre-injector up to 45 mA. We will present the status of the modelling of the pre-injector and possible solutions to reach higher beam currents from the RFQ along with results from the reliability run.

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reference for this paper ※ https://doi.org/10.18429/JACoW-IPAC2019-MOPTS096

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paper received ※ 30 April 2019 paper accepted ※ 19 May 2019 issue date ※ 21 June 2019

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MOPTS101

Study of the Transverse Emittance Blow-Up Along the Proton Synchrotron Booster Cycle During Wire Scanner Operation

emittance, proton, scattering, brightness

1110

A. Santamaría García, F. Antoniou, H. Bartosik, J.A. Briz Monago, G.P. Di Giovanni, A. Guerrero, J.R. Hunt, B. Mikulec, F. Roncarolo, E. Senes, V. Vlachoudis
CERN, Geneva, Switzerland
E. Senes
Oxford University, Physics Department, Oxford, Oxon, United Kingdom

Transverse emittance measurements with wire scanners have been extensively studied across the accelerator complex at CERN due to their important role in characterizing the beam and their complicated modeling. In recent years, this topic has been of particular interest for the LHC Injectors Upgrade (LIU) project, where a tight transverse emittance blow-up budget between the Proton Synchrotron Booster (PSB) and the Proton Synchrotron (PS) is imposed to assure the required beam brightness for the High Luminosity LHC (HL-LHC). In order to maintain a high brightness beam, any source of emittance blow-up along the PSB cycle needs to be identified and mitigated. While wire scanners have been mostly used at extraction energy in the PSB, they can also operate along the energy cycle. The scattering of the protons with the wire increases considerably at lower energies, leading to an overestimation of the beam emittance. In this contribution we present the most recent studies, focusing on precisely quantifying the blow-up created by the flying wire with measurements in an optimized set-up and compared to FLUKA simulations.

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reference for this paper ※ https://doi.org/10.18429/JACoW-IPAC2019-MOPTS101

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paper received ※ 13 May 2019 paper accepted ※ 20 May 2019 issue date ※ 21 June 2019

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MOPTS104

A Toolkit for Tracing Electron Beam Envelope at Low Energy Section of TPS Linac

electron, linac, operation, gun

1122

H.H. Chen, H.C. Chen, K.-K. Lin, Y.K. Lin
NSRRC, Hsinchu, Taiwan

Based on calculated Bz of solenoids installed at the TPS linac low energy section, the electron beam envelope along beam centerline has been explored in this work using the initial and boundary conditions provided in the linac specifications. Concept of magnetic flux compression is adopt to analyze the beam size variation along linac centerline. The calculated result of selected checkpoints has been experimentally verified using screen monitors. In order to benefit tuning capability in routine operation, the display of beam size variation along centerline is integrated into the previously developed toolkit ’linac’. It is hope that it will provide an interactive approach for linac tune-up process and would be helpful to its routine operation.

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reference for this paper ※ https://doi.org/10.18429/JACoW-IPAC2019-MOPTS104

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paper received ※ 23 April 2019 paper accepted ※ 20 May 2019 issue date ※ 21 June 2019

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MOPTS110

FLUKA-MARS15 Simulations To Optimize the Fermilab PIP-II Movable Beam Absorber

linac, MMI, shielding, radiation

1136

L. Lari, F.G. Garcia, Y. He, I. Kourbanis, N.V. Mokhov, E. Pozdeyev, I.L. Rakhno
Fermilab, Batavia, Illinois, USA
F. Cerutti, L.S. Esposito, L. Lari
CERN, Meyrin, Switzerland

PIP-II is the Fermilab’s flagship project to provide powerful, high-intensity proton beams to the laboratory’s experiments. The heart of the PIP-II project is an H⁻ 800 MeV superconducting linear accelerator. In order to commission the beam and operate safely the linac, several constraints were evaluated. The design of a movable 5 kW beam absorber was finalized to allow staged beam commissioning in different linac locations. Prompt and residual radiation levels were calculated, and radiation shields were optimized to keep those values within the acceptable levels in the areas surrounding beam absorber. Monte Carlo calculations with FLUKA and MARS15 codes are presented in the paper to support these studies.

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reference for this paper ※ https://doi.org/10.18429/JACoW-IPAC2019-MOPTS110

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paper received ※ 14 May 2019 paper accepted ※ 20 May 2019 issue date ※ 21 June 2019

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MOPTS118

3D Electromagnetic/PIC Simulations for a Novel RFQ/RFI Linac Design

rfq, linac, neutron, operation

1158

S.J. Smith, S. Biedron, A.M.N. Elfrgani, E. Schamiloglu, S.I. Sosa Guitron
University of New Mexico, Albuquerque, USA
P.G. Bethoney, M.S. Curtin, B. Hartman, T. Pressnall, D.A. Swenson
Ion Linac Systems, Inc., Albuquerque, USA
T.B. Bolin
Element Aero, Chicago, USA
J.R. Cary, D.M. Cheatham
Tech-X, Boulder, Colorado, USA

Funding: This work was supported by Ion Linac Systems, Albuquerque, NM.
Using the commercial software VSim 9, a highly parallelized particle-in-cell/finite difference time-domain modeling code, the performance of an existing novel RFQ/RFI linac structure designed by Ion Linac Systems is evaluated. This effort is aimed towards having an up to date full 3D start-to-end simulation of the accelerator system, which does not exist currently. The structure used is an efficient 200-MHz, 2.5-MeV, CW-RFQ/RFI proton linac. The methods employed in VSim for modelling and parameter setup are presented, along with the simulation procedures for both the Electromagnetic and PIC solver. The important figures of merit for the structure are given including the Q-factor, field distributions, shunt impedance, and important beam properties. These are then contrasted with the initial design values and analytical calculations.

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reference for this paper ※ https://doi.org/10.18429/JACoW-IPAC2019-MOPTS118

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paper received ※ 15 May 2019 paper accepted ※ 21 May 2019 issue date ※ 21 June 2019

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MOPTS120

Commissioning of the New Experimental FODO Line at the SNS Beam Test Facility

rfq, emittance, MMI, optics

1164

A.V. Aleksandrov, S.M. Cousineau, K.J. Ruisard, V. Tzoganis, A.P. Zhukov
ORNL, Oak Ridge, Tennessee, USA
Z.L. Zhang
UTK, Knoxville, Tennessee, USA

The SNS Beam Test Facility consists of a 2.5MeV proton accelerator and a beam line with various diagnostics for high intensity beam dynamics study. A FODO line consisting of 19 quadrupole magnets and a large dynamic range emittance monitor has been added recently. The new setup is design for experimental study of mechanisms of halo formation in mismatched high intensity beams. We present results of the new beam line commissioning with beam.

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reference for this paper ※ https://doi.org/10.18429/JACoW-IPAC2019-MOPTS120

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paper received ※ 07 May 2019 paper accepted ※ 21 May 2019 issue date ※ 21 June 2019

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TUZPLM1

Adding Data Science and More Intelligence to Our Accelerator Toolbox

controls, network, electron, laser

1191

S. Biedron
University of New Mexico, Albuquerque, USA
S. Biedron
Element Aero, Chicago, USA

Requirements for recent accelerators are becoming more and more stringent and sophisticated machine tuning is necessary. A large amount of data is acquired from accelerator components as an assistant of machine tuning. It is hard for operators to utilize all the accelerator data for machine tuning. Therefore, machine learning, data mining and big data handling are recently applied to accelerators. For instance, Bayesian optimization is used for maximizing a target performance, a clustering algorithm is used for anomaly detection, and hidden correlation finding is utilized for discovering new aspects of a machine. This talk reviews recent progress of machine learning applications and big data handling in accelerators.

Slides TUZPLM1 [11.978 MB]

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reference for this paper ※ https://doi.org/10.18429/JACoW-IPAC2019-TUZPLM1

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paper received ※ 20 May 2019 paper accepted ※ 16 June 2019 issue date ※ 21 June 2019

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TUPMP011

Storageless Resonant Converter for Accelerator Magnets

operation, resonance, controls, storage-ring

1248

M. Cautero, T.N. Gucin
Elettra-Sincrotrone Trieste S.C.p.A., Basovizza, Italy

Elettra Sincrotrone Trieste, a specialized research centre generating high quality synchrotron radiation, has been in operation since 1993 and was revised in 2009. Recently, Elettra has been funded for a complete renewal of the storage ring. For the new machine, it is planned to employ state of the art converters, mostly of which will be designed in-house. For this purpose, it has been decided to evaluate the performance of a storage-less resonant converter, pro-posed by Dr. Slobodan Ćuk, which is a step down DC/DC converter consisting of four switches, one resonant capac-itor and two resonant inductors. For this purpose, the voltage conversion ratio of the converter has been de-rived. The topology was confirmed with simulation and a PCB layout has been designed, which is still to be tested.

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reference for this paper ※ https://doi.org/10.18429/JACoW-IPAC2019-TUPMP011

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paper received ※ 08 May 2019 paper accepted ※ 23 May 2019 issue date ※ 21 June 2019

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TUPMP017

Design of Scanning Magnet Power Supply for HUST-PTF

power-supply, target, controls, proton

1269

X.Y. Li, Y.Y. Hu, Y.J. Lin, P. Tan, X.D. Tu, Y.C. Yu, L.G. Zhang, Z.Q. Zhang
HUST, Wuhan, People’s Republic of China

An active scanning proton therapy facility is being de-veloped at Huazhong University of Science and Technol-ogy（HUST）. By controlling the deflection position of the beam with scanning magnets at different times, the superposition of discrete spot beams will form a specified shape and dose distribution conformal to the target tu-mour. A high precision and fast response power supply is required to deflect the beam quickly and accurately. In this paper, the TOSCA module in Opera3D is used to model and simulate the scanning magnets and to obtain the equivalent inductance of the magnet. Then the calcu-lated equivalent resistance inductance instead of the magnet is used to design the scanning magnet power supply. A high-voltage bridge is utilized to achieve fast response speed, and a low voltage bridge and PI control algorithm is adopted to ensure power supply accuracy. The Simulation result shows that the designed power supply meets the requirements of response speed and accuracy.

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reference for this paper ※ https://doi.org/10.18429/JACoW-IPAC2019-TUPMP017

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paper received ※ 30 April 2019 paper accepted ※ 22 May 2019 issue date ※ 21 June 2019

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TUPMP019

Vacuum Performance of the NEG-coated Chamber for U#19 at PF-ring

vacuum, photon, MMI, undulator

1276

Y. Tanimoto, T. Honda, X.J. Jin, T. Nogami, R. Takai, M. Yamamoto
KEK, Ibaraki, Japan

At the Photon Factory storage ring (PF-ring) in KEK, a new APPLE-II type elliptically polarizing undulator (U#19) was installed in October 2018. The U#19 vacuum chamber is 4.1 meters in length, and the beam channel with a 15x90 elliptical profile and two cooling-water channels alongside were formed by extrusion of A6060-T6 aluminum alloy. The inner surface of the beam channel is coated with a Ti-Zr-V Non-Evaporable Getter (NEG) thin film, as it has a high effective pumping speed and a low Photon Stimulated Desorption (PSD) yield. After the installation of the U#19, the neighboring uncoated chambers and vacuum components were baked out at 200 °C for 44 hours, and then the NEG coating was activated at 160 °C for 48 hours. As a result, the pressures in the neighboring chambers reached as low as 10^-8 Pa. The conditioning of the vacuum chambers with irradiation of Synchrotron radiation evolved favorably as had been expected by a combined simulation of Synrad and Molflow, leading to a satisfactory recovery of the beam lifetime. Vacuum performance of the NEG-coated chamber was assessed especially by means of a residual gas analysis, and the properties of the NEG film were characterized by surface analyses including SEM, EDX, and XRD.

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reference for this paper ※ https://doi.org/10.18429/JACoW-IPAC2019-TUPMP019

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paper received ※ 16 May 2019 paper accepted ※ 22 May 2019 issue date ※ 21 June 2019

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TUPMP023

Design of Digital Controller for Multi Module Series-parallel Accelerator Power Supply

power-supply, controls, hardware, software

1288

J. Li, Y. Liu, X. Qi, W.Q. Zhang
IHEP, Beijing, People’s Republic of China

Funding: Supported by funds, Key laboratory of particle Acceleration Physics & Technology, Institute of High Energy Physics, Chinese Academy of Sciences，Project number：Y5294107TD
With the development of accelerators, Accelerator physics require power supply output high voltage and current (Peak power reached MWs). And the current stability requirements better than 10ppm. Therefore, the power supply is mostly used in the mode of module series-parallel. However, during actual commissioning, the power supply often does not run at rated current. If the power supply is running at less than 30% of the rated current, the power output current stability will drop sharply. This topic designed a set of digital controller for multi-module serial-parallel control. The digital controller can automatically adjust the number of input modules according to the current setting, and can automatically allocate the required PWM number of the module. While taking into account the synchronization between the various modules, Ensure the power supply is always running at an optimal working condition. Through a special AD conversion hardware design and advanced closed-loop controller algorithm, the digital controller can provide up to 20 high-resolution PWM signals to drive power conversion devices.

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reference for this paper ※ https://doi.org/10.18429/JACoW-IPAC2019-TUPMP023

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paper received ※ 14 May 2019 paper accepted ※ 23 May 2019 issue date ※ 21 June 2019

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TUPMP025

Design of Fast Corrector Magnet Power Supply for HEPS

power-supply, controls, experiment, radiation

1294

P. Liu, C. Han, F. Long
IHEP, Beijing, People’s Republic of China

High energy photon source is a fourth-generation synchrotron radiation light source with energy of 6Gev and ultra-low emittance (<0.1nm’rad). The ultra-low beam emittance requires high beam stability. Therefore, we develop a fast correction power supply with high bandwidth and low current ripple to improve the performance of the fast close orbit correction sys-tem to prove the high beam stability. The power supply adopts FPGA for full-digital control and use high speed ADC with temperature control. The power sup-ply has a small signal-bandwidth of 10 kHz and output current ripple lower than 20ppm. In this paper, we will describe the hardware design and software control methods and the test results will be demonstrated

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reference for this paper ※ https://doi.org/10.18429/JACoW-IPAC2019-TUPMP025

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paper received ※ 13 May 2019 paper accepted ※ 22 May 2019 issue date ※ 21 June 2019

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TUPMP033

Design of the Neutron Imaging Differential Pumping Line at LLNL

neutron, target, vacuum, shielding

1312

J.A. Caggiano, D. Castronovo, P. Fitsos, D.J. Gibson, J. Hall, M.S. Johnson, R.A. Marsh, B. Rusnak
LLNL, Livermore, California, USA

Funding: This work performed under the auspices of the U.S. Department of Energy by Lawrence Livermore National Laboratory under Contract DE-AC52-07NA27344.
The neutron imaging system at LLNL is a radiographic capability for imaging objects with fast, quasi-monoenergetic neutrons at ≤1mm spatial resolution. The neutron production source is a deuteron beam (4 or 7 MeV) incident upon a rotating, high-pressure, windowless, pure-deuterium gas target. The windowless nature of the target combined with the high pressure leads to significant gas leakage upstream of the neutron production target. This leakage degrades the imaging quality by (1) increasing the depth-of-field blurring and (2) increasing the beam diameter and divergence in the transverse direction via angular straggling in the residual gas. To mitigate these effects, and guided by bench tests and simulations, we designed a differential pumping line (DPL) to ensure the highest quality imaging system. The system consists of three primary stages (chambers), each separated by carefully shaped apertures. These apertures can be long and thin with low-angle tapers due to the high quality of the beam optics (convergence at the target < 5mrad) and low emittance of the beam (~5 pi mm-mrad). The primary cascaded roots pumps are sized to remove >99% of the incoming mass flow in each stage, ensuring that by the third stage furthest from the target, turbomolecular pumps are able to operate in a nominal ~mTorr range. We anticipate full system testing with helium in mid 2019.

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paper received ※ 30 April 2019 paper accepted ※ 22 May 2019 issue date ※ 21 June 2019

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TUPMP037

Recent Developments of Monte-Carlo Codes Molflow+ and Synrad+

vacuum, photon, synchrotron, synchrotron-radiation

1327

R. Kersevan, M. Ady
CERN, Geneva, Switzerland

Molflow+ and Synrad+ are Monte Carlo simulation tools for ultra-high vacuum and synchrotron radiation, respectively. Over the years they have become a common tool for designing and analysing the vacuum system of particle accelerators. This contribution gives a short summary about new features added since IPAC-14*. Some highlights: In traditional Monte Carlo simulations, one simulated ’virtual’ particle represents a given number of physical molecules or photons. This is a weakness where the pressure or flux of the simulated system spans across multiple orders of magnitude. Synrad now supports low flux mode, a weighed Monte Carlo technique where the represented number of photons is reduced at every reflection, providing significantly better statistics at low flux regions. As for Molflow+, angle maps allow recording the molecules, directional distribution at any point, and then desorb a reduced gas quantity according to the recording. In linear systems, this allows iterative simulations that have been proven to treat systems up to 7 orders of magnitude of pressure difference. Without the new technique the computing time would be prohibitively slow on desktop computers, which is what most users of the two codes use. Both codes now have a built-in geometry builder that allows creating simple models through a set of 3D operations, and modifying those imported from CAD tools. Molflow+ has recently become open source, and it has been made compatible with, and tested on different versions of Linux and macOS. Examples of application of Molflow+ to novel Beam Gas Curtain detector and the design of the FCC-ee vacuum system will be given, alongside with some benchmarking runs against data published in literature.
* M. Ady, R. Kersevan, "Introduction to the Latest Version of the Test-particle Monte Carlo Code Molflow+", Proc. IPAC’14, Dresden, Germany, June 2014, pp. 2348-2350.

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paper received ※ 13 May 2019 paper accepted ※ 23 May 2019 issue date ※ 21 June 2019

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TUPMP040

Impact of Flux Jumps on High-Precision Powering of Nb₃Sn Superconducting Magnets

experiment, controls, superconducting-magnet, superconductivity

1338

M. Martino, P. Arpaia, S. Ierardi
CERN, Geneva, Switzerland

Nb₃Sn superconducting magnets represent a technology enabler for future high-energy particle accelerators. A possible impediment, though, comes from flux jumps that, so far, could not be avoided by design unlike for NbTi technology. However, the impact of flux jumps on the powering has not been properly investigated to date. Flux jumps appear during current ramps at relatively low value of current and tend to disappear towards nominal current. They are usually detected as voltage jumps between different magnet coils but they might also produce overall voltage jumps across the magnet electrical terminals. Such jumps might perturb the power converter feedback control loop and therefore potentially jeopardize its precision performance during energy ramps. This work aims at : (i) presenting preliminary experimental test results on some HL-LHC Nb₃Sn model and prototype magnets, and (ii) attempting to build a simplified electrical model of the flux jumps (with focus only at its interaction with the power converter feedback control loop). Such work is a starting point for outlining possible power converters control strategies able to minimize flux jumps impact on high-precision powering of Nb₃Sn superconducting magnets.

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paper received ※ 23 April 2019 paper accepted ※ 22 May 2019 issue date ※ 21 June 2019

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TUPGW012

Sensitivity Studies of the PETRA IV Lattice

alignment, emittance, site, resonance

1408

I.V. Agapov
DESY, Hamburg, Germany

As the machine with the smallest emittance among the planned fourth-generation hard x-ray synchrotron light sources, PETRA IV will have very demanding requirements on magnet alignment and stability. Several developments to address mechanical and beam-based stabilization have been started in connection to that. Here we summarize the alignment and field error tollerances resulting from startup and commissioning simulations of the main ring. Novel high level control tools will be required to assure smooth operation of the machine; progress in their development and beam test results at PETRA III will be reported.

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paper received ※ 15 May 2019 paper accepted ※ 22 May 2019 issue date ※ 21 June 2019

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TUPGW013

Tune and Chromaticity Optimization at Bessy II for the Transverse Resonant Island Bucket Optics

optics, photon, resonance, emittance

1411

F. Armborst, P. Goslawski, A. Jankowiak
HZB, Berlin, Germany

Funding: Federal Ministry of Education and Research
Transverse Resonant Island Buckets (TRIBs *) correspond to a second stable orbit, longitudinally winding around the core orbit in the transverse x-x^′-phasespace. The exploitation possibilities for stable TRIBs are under investigation at the third generation light source BESSY II in Berlin. The applicability for bunch separation is a main subject of these studies. Stable operation of TRIBs optics with a single or few bunches on the second orbit and a multibunch train on the main orbit has been shown **. Photons emitted on the second orbit are well separated from those of the main orbit at all beamlines. This provides the possibility of bunch separation by beamline adjustment for the timing community without significant impact on the average brightness for other users. Simulations based on linear optics from closed orbits (LOCO) and on nonlinear optics derived from the measured chromaticity and tune shift with action (TSWA) predict this separation well. Friendly user experiments in 2018 confirmed these results. The scheduled upgrade BESSY VSR *** features simultaneously stored long and short bunches. Then TRIBs optics would in principle enable the separation of the different bunches at every beamline offering unique possibilities to our users. Simulations and measurements aiming to investigate further possible optimization of the TRIBs optics are presented.
* F. Armborst, P. Goslawski et al, DOI: 10.18429/JACoW-IPAC2018-TUPML052
** P. Goslawski, F. Armborst et al. DOI: 10.18429/JACoW-IPAC2017-WEPIK057
*** A. Jankowiak et al., DOI: 10.5442/R0001

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reference for this paper ※ https://doi.org/10.18429/JACoW-IPAC2019-TUPGW013

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paper received ※ 14 May 2019 paper accepted ※ 18 May 2019 issue date ※ 21 June 2019

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TUPGW016

New Operation Regimes at the Storage Ring KARA at KIT

lattice, optics, operation, injection

1422

A.I. Papash, E. Blomley, T. Boltz, M. Brosi, E. Bründermann, S. Casalbuoni, J. Gethmann, E. Huttel, B. Kehrer, A. Mochihashi, A.-S. Müller, R. Ruprecht, M. Schuh, J.L. Steinmann
KIT, Karlsruhe, Germany

The storage ring Karlsruhe Research Accelerator (KARA) at KIT operates in a wide energy range from 0.5 to 2.5 GeV. Initially, the ring was designed to serve as a Light Source for synchrotron radiation facility ANKA. Since then different operation modes have been implemented at KARA: in particular, the double bend achromat (DBA) lattice with non-dispersive straight sections, the theoretical minimum emittance (TME) lattice with distributed dispersion, and different versions of low compaction factor optics with highly stretched dispersion function. Short bunches of a few ps pulse width are available at KARA. Low alpha optics have been tested and implemented in a wide operational range of the ring and are now routinely used at 1.3 GeV for studies of CSR-induced beam dynamics and THz bursting in the micro-bunching instability. Different non-linear effects, in particular, residual high order components of magnetic fields generated in insertion devices have been studied and cured. A new operation mode at high vertical tune implemented at KARA essentially improves beam performance during user operation as well as at low alpha regimes.

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reference for this paper ※ https://doi.org/10.18429/JACoW-IPAC2019-TUPGW016

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paper received ※ 23 April 2019 paper accepted ※ 22 May 2019 issue date ※ 21 June 2019

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TUPGW019

Progress of the BESSY VSR Cold String Development and Testing

cavity, GUI, experiment, vacuum

1434

H.-W. Glock, V. Dürr, F. Glöckner, J. Knobloch, M. Tannert, A.V. Vélez, D. Wolk, N. Wunderer
HZB, Berlin, Germany
J. Guo, R.A. Rimmer, H. Wang
JLab, Newport News, Virginia, USA

The so-called VSR (Variable Storage Ring) upgrade of the 3rd gen. light source BESSY II will provide the capability to simultaneously store long (about 20 ps rms length) and short (1 ps or less) bunches in the ring. This will be accomplished by inserting a module with four superconducting cavities, two of them operating at 1.5 GHz as the third harmonic of the 500 MHz driving RF, two at 1.75 GHz. The "cold" string of those four cavities also includes supporting and connecting devices, as there will be: - three intermediate bellows, all shielded against leaking fundamental mode cavity fields, one additionally acting as a collimator for incident synchrotron light; - two tuneable bellows at the module ends; - two warm end groups outside the module, housing toroidal dielectric wake field absorbers, another bellow and a vacuum pump connection. The recent design progress of those components will be reported, including a description of a beam test planned for the central collimating shielded bellow.

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reference for this paper ※ https://doi.org/10.18429/JACoW-IPAC2019-TUPGW019

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paper received ※ 22 May 2019 paper accepted ※ 23 May 2019 issue date ※ 21 June 2019

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TUPGW021

An Accelerator Toolbox (AT) Utility for Simulating the Commissioning of Storage-Rings

MMI, lattice, injection, alignment

1441

T. Hellert, Ph. Amstutz, C. Steier, M. Venturini
LBNL, Berkeley, California, USA

We present the development of an AT-based toolkit, which allows for realistic commissioning simulations of storage ring light sources by taking into account a multitude of error sources as well as diligently treating beam diagnostic limitations.

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reference for this paper ※ https://doi.org/10.18429/JACoW-IPAC2019-TUPGW021

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paper received ※ 08 April 2019 paper accepted ※ 18 May 2019 issue date ※ 21 June 2019

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TUPGW022

Commissioning Simulation Study for the Accumulator Ring of the Advanced Light Source Upgrade

MMI, injection, lattice, quadrupole

1445

T. Hellert, Ph. Amstutz, M.P. Ehrlichman, S.C. Leemann, C. Steier, C. Sun, M. Venturini
LBNL, Berkeley, California, USA

The Advanced Light Source Upgrade (ALS-U) to a diffraction-limited soft x-rays light source requires the construction of an Accumulator Ring (AR) to enable swap-out, on-axis injection. The AR lattice is a Triple-Bend-Achromat lattice similar to that of the current ALS but to minimize the magnet sizes the vacuum chamber will be significantly narrower hence requiring a careful evaluation of the magnets’ field quality. This work presents the results of a detailed error tolerance study including a complete simulation of the commissioning process.

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reference for this paper ※ https://doi.org/10.18429/JACoW-IPAC2019-TUPGW022

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paper received ※ 14 May 2019 paper accepted ※ 22 May 2019 issue date ※ 21 June 2019

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TUPGW043

Simulation of Model Independent Analysis to HEPS Storage Ring

optics, quadrupole, storage-ring, betatron

1504

D. Ji, Y. Jiao, H.Z. Ma, J.H. Yue
IHEP, Beijing, People’s Republic of China

Model Independent Analysis (MIA) is a beam analysis method applied for Turn-by-Turn (TBT) Beam Position Monitor (BPM) data. To develop the commissioning method of the HEPS storage ring, we simulate application of MIA on HEPS storage error model to measure and cor-rect the optics parameters. Difficulties and limitations of the MIA method are also discussed.

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reference for this paper ※ https://doi.org/10.18429/JACoW-IPAC2019-TUPGW043

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paper received ※ 15 May 2019 paper accepted ※ 22 May 2019 issue date ※ 21 June 2019

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TUPGW053

Simulations of the Injection Transient Instabilities for the High Energy Photon Source

injection, feedback, lattice, storage-ring

1524

Z. Duan, N. Wang, H.S. Xu
IHEP, Beijing, People’s Republic of China

Funding: Work supported by Natural Science Foundation of China (No.11605212).
A "charge recovery in booster" scheme* was proposed to deliver the full charge bunches for the swap-out injection of the High Energy Photon Source. In this scheme, the booster is employed also as a full energy accumulator ring to capture the high charge bunch extracted from the storage ring via merging with the small charge bunch accelerated in the booster, after enough damping in the booster for about 20 ms, the recovered full charge bunch is re-injected into the storage ring. This scheme avoids the challenges to accelerate a bunch charge of ~ 15 nC, and is cost effective compared to building a dedicated 6 GeV accumulator ring. However, there will be a period of time during injection that one bunch is missing in the storage ring, which inevitably introduces some injection transients. Since "transparency" to the user experiments is a desired feature of injection schemes for next generation diffraction-limited storage rings, the injection transient effects are simulated for the proposed injection scheme, and how it would affect the user experiments are carefully evaluated.
* Z. Duan, et al., "The swap-out injection scheme for the High Energy Photon Source", Proc. IPAC’18, THPMF052

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reference for this paper ※ https://doi.org/10.18429/JACoW-IPAC2019-TUPGW053

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paper received ※ 15 May 2019 paper accepted ※ 23 May 2019 issue date ※ 21 June 2019

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TUPGW063

Studying the Dynamic Influence on the Stored Beam From a Coating in a Multipole Injection Kicker

injection, emittance, operation, kicker

1547

J. Kallestrup, Å. Andersson, J. Breunlin, D.K. Olsson, P.F. Tavares
MAX IV Laboratory, Lund University, Lund, Sweden
P. Alexandre, R. Ben El Fekih
SOLEIL, Gif-sur-Yvette, France

The MAX IV 3 GeV ring is the first synchrotron light source utilizing the Multi-Bend Achromat scheme to achieve a low horizontal bare-lattice emittance of 328 pm rad providing high brilliance x-rays for users. A novel Multipole Injection Kicker (MIK) designed and constructed by SOLEIL is used to allow top-up operation with only minor disturbances to the stored beam, i.e., the users. We investigate the stored beam perturbations due to quadrupole fields arising during the MIK pulse, originating from its inner coating. Maximum bunch emittance growth of §I{21}{πco\meter\radian} was found in simulations. Measurements of the stored beam impact are performed and found to be in good agreement with simulations. We conclude that the MIK at MAX IV 3 GeV has the potential to deliver quasi-transparent injections with good capture efficiency.

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reference for this paper ※ https://doi.org/10.18429/JACoW-IPAC2019-TUPGW063

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paper received ※ 06 May 2019 paper accepted ※ 17 May 2019 issue date ※ 21 June 2019

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TUPGW072

Design and Optimization of Full Energy Injector Linac for Siam Photon Source II

linac, storage-ring, injection, emittance

1570

T. Chanwattana, P. Klysubun, T. Pulampong, P. Sudmuang
SLRI, Nakhon Ratchasima, Thailand

The new Thailand synchrotron light source, Siam Photon Source II (SPS-II), has been designed based on a 3 GeV storage ring with a Double-Triple Bend Achromat (DTBA) lattice and a full energy injector linac. The linac consists of an S-band photocathode RF gun, C-band accelerating structures and two magnetic chicanes. In addition to its main function as the storage ring injector, the linac is capable of producing sub-picosecond electron bunches for additional short-pulse beamlines at the end of the linac. The linac also has a potential to become a driver of a soft X-ray Free Electron Laser (FEL) operating adjacent to the storage ring. In this paper, start-to-end simulations of the full energy linac are presented. Optimization was performed in order to fulfil requirements for both storage ring injection and short pulse generation.

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reference for this paper ※ https://doi.org/10.18429/JACoW-IPAC2019-TUPGW072

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paper received ※ 14 May 2019 paper accepted ※ 22 May 2019 issue date ※ 21 June 2019

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TUPGW076

Early Commissioning Simulation of the Diamond Storage Ring Upgrade

MMI, optics, quadrupole, closed-orbit

1577

H. Ghasem, M. Apollonio, R. Bartolini, J.P. Kennedy, I.P.S. Martin
DLS, Oxfordshire, United Kingdom

A low beam emittance lattice has been designed for up-grade of the Diamond storage ring. Due to the use of strong focusing elements and rather small vacuum cham-ber and considering the required short dark time, commis-sioning of the designed storage ring becomes very chal-lenging. This paper briefly explains the progress of early commissioning simulations of the storage ring, gives the required engineering tolerances, presents the first simula-tion results and discusses the non-linear beam dynamics (NLBD) issues after successful commissioning with and without insertion devices (IDs).

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reference for this paper ※ https://doi.org/10.18429/JACoW-IPAC2019-TUPGW076

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paper received ※ 13 May 2019 paper accepted ※ 22 May 2019 issue date ※ 21 June 2019

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TUPGW078

Harmonic Cavity Design Choice for Lifetime Increase in Diamond-II

cavity, beam-loading, lattice, storage-ring

1585

T. Olsson, R. Bartolini, I.P.S. Martin
DLS, Oxfordshire, United Kingdom

The ongoing trend towards synchrotron light storage rings with ultralow emittance leads to a requirement for strong magnet gradients, which reduce the dynamic aperture and thus the Touschek lifetime of the machine. This is also the case for the planned upgrade of the Diamond Light Source. One option to increase the Touschek lifetime is to lengthen the electron bunches with a harmonic cavity operated close to a harmonic of the fundamental RF frequency. This paper presents studies of a harmonic cavity for Diamond-II with the focus on maximising the lifetime increase. It is foreseen that the ring will have to operate with a gap in the fill pattern to avoid instabilities and therefore multiparticle tracking was used to determine the effect on stability and lifetime for various cavity parameters taking into account transient beam loading.

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reference for this paper ※ https://doi.org/10.18429/JACoW-IPAC2019-TUPGW078

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paper received ※ 14 May 2019 paper accepted ※ 18 May 2019 issue date ※ 21 June 2019

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TUPGW089

Tunable Bunch Train Generation Using Emittance Exchange Beamline With Transverse Wiggler

wiggler, controls, emittance, bunching

1612

G. Ha, M.E. Conde, J.G. Power, J.H. Shao, E.E. Wisniewski
ANL, Argonne, Illinois, USA

Funding: This work is supported by LDRD program at Argonne National Laboratory and Department of Energy, Office of High Energy Physics, under Contract No. DE-AC02-06CH11357.
Emittance exchange beamline provides a unique correlation between the upstream transverse momentum and downstream longitudinal timing. Similar to the bunch train generation concept using energy modulation and chicane, the emittance exchange beamline can convert the transverse momentum modulation to the temporal modulation at the end of the beamline. The beam can obtain this transverse modulation from alternating magnet array (e.g. 90 degree rotated undulator). While most of other methods provide only one knob to control both micro-bunch length and bunch-to-bunch spacing or hard to control one of the knobs, this method provides separated knobs for the micro-bunch length and spacing and they are easy to control. These knobs enable to separately control the fundamental frequency of the radiation and its bandwidth. We plan to demonstrate this method at Argonne Wakefield Accelerator facility (AWA). This poster present progress on this new method and its demonstration at AWA.

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reference for this paper ※ https://doi.org/10.18429/JACoW-IPAC2019-TUPGW089

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paper received ※ 21 May 2019 paper accepted ※ 23 May 2019 issue date ※ 21 June 2019

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TUPGW090

Experimental Tests of the Automated APS-U Commissioning Algorithm at APS

MMI, lattice, sextupole, closed-orbit

1615

V. Sajaev
ANL, Argonne, Illinois, USA

Funding: Work supported by the U.S. Department of Energy, Office of Science, Office of Basic Energy Sciences, under Contract No. DE-AC02- 06CH11357
APS Upgrade (APS-U) will feature hybrid seven-bend achromat lattice with very strong focusing elements and relatively small vacuum chamber aperture. Achieving design lattice parameters during commissioning will need to be accomplished quickly in order to minimize dark time for APS users. The paper will describe the automated start-to-end lattice commissioning algorithm starting with the first-turn trajectory correction and ending with the lattice correction. It will then show simulation results of the APS-U commissioning, and finally present results of the experimental tests of the commissioning at the existing APS.

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reference for this paper ※ https://doi.org/10.18429/JACoW-IPAC2019-TUPGW090

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paper received ※ 15 May 2019 paper accepted ※ 23 May 2019 issue date ※ 21 June 2019

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TUPGW107

Overview of Collective Effects in SLS 2.0

cavity, impedance, operation, damping

1658

M.M. Dehler, M. Aiba, A. Citterio, L. Stingelin
PSI, Villigen PSI, Switzerland

At the end of 2017, the conceptual design for an upgrade of the Swiss Light Source was finished, promising a 40 fold smaller emittance and a corresponding increase of the spectral brightness from the current value. From the point of view of collective effects, the main changes in the new design are a reduced chamber size, fully coated with NEG, and operation at small and negative momentum compaction with low synchrotron frequency. We give an overview of the latest results for the ring. Most critical is the threshold for the longitudinal single bunch instability. Taking into account the combined effect of wake impedances and CSR, we have to rely on bunch stretching by a higher harmonic system to achieve stable operation at nominal current.

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reference for this paper ※ https://doi.org/10.18429/JACoW-IPAC2019-TUPGW107

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paper received ※ 14 May 2019 paper accepted ※ 22 May 2019 issue date ※ 21 June 2019

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TUPRB004

Magnetic Measurements of Insertion Devices Using the Vibrating Wire Technique

experiment, vacuum, insertion-device, hardware

1683

C.K. Baribeau, D. Bertwistle, E.J. Ericson, J.T. Gilbert, T.M. Pedersen
CLS, Saskatoon, Saskatchewan, Canada

The commissioning of new in-vacuum insertion devices (ID) at the Canadian Light Source has motivated the assembly and development of a vibrating wire system. The advantage of the technique is that it is a sensitive magnetic measurement instrument at relatively low cost. Moreover, most hall probe systems require transverse access, which is often not available for in-vacuum or Delta-like devices. It is comparatively simple to string a taut wire through the gap of an in-vacuum ID. We describe the experimental challenges in mapping the field of an 80 mm period in-vacuum wiggler, IVW80, using the vibrating wire technique, and compare results against simulation and data obtained from Hall probe measurements.

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reference for this paper ※ https://doi.org/10.18429/JACoW-IPAC2019-TUPRB004

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paper received ※ 08 May 2019 paper accepted ※ 22 May 2019 issue date ※ 21 June 2019

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TUPRB005

Photon Polarisation Modelling of APPLE-II EPUs

polarization, photon, undulator, operation

1687

M.J. Sigrist, C.K. Baribeau, T.M. Pedersen
CLS, Saskatoon, Saskatchewan, Canada

The CLS is currently commissioning two APPLE-II in-sertion devices (IDs), see [1], and constructing two more that allow for operation in ’universal mode’, i.e. selecting arbitrary photon polarisation parameters. Two of these devices will operate in the soft x-ray range where there is expected to be a significant change to polarisation at the sample due to transmission effects of the beam line op-tics. Arbitrary polarisation selection of the ID will counter transmission effects and enable circular polarisation at the sample position. A polarisation model of the device is derived which allows for the calculation of both the Stokes parameters and photon energy for any set point of ID gap and phase. Numerical solutions of these equa-tions allow the calculation of gap and phase set points for any desired photon energy or polarisation. The results of the polarisation model are compared with numerical simulations of the synchrotron radiation calculated using measured magnetic fields at various polarisation modes.

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reference for this paper ※ https://doi.org/10.18429/JACoW-IPAC2019-TUPRB005

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paper received ※ 13 May 2019 paper accepted ※ 18 May 2019 issue date ※ 21 June 2019

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TUPRB010

FIRST DESIGN STUDIES OF A NC CW RF GUN FOR EUROPEAN XFEL

gun, cathode, cavity, FEL

1698

G. Shu, Y. Chen, S. Lal, H.J. Qian, H. Shaker, F. Stephan
DESY Zeuthen, Zeuthen, Germany

After the successful commissioning of the European XFEL in pulsed mode, continuous wave (CW) mode operation of European X-ray Free-Electron Laser (XFEL) is under considerations for future upgrade. DESY is push-ing R&D on CW electron sources. A fully superconducting CW gun is under experimental development at DESY in Hamburg, and a normal conducting (NC) CW gun is under physics design at the Photo Injector Test facility at DESY in Zeuthen (PITZ) as a backup option. A 217 MHz NC CW gun is developed from the LBNL 187 MHz VHF gun, with enhancement on both cathode gradient and gun voltage to further improve beam brightness. This paper presents the cavity RF design, multipacting (MP) simula-tions and beam dynamics studies.

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reference for this paper ※ https://doi.org/10.18429/JACoW-IPAC2019-TUPRB010

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paper received ※ 17 May 2019 paper accepted ※ 20 May 2019 issue date ※ 21 June 2019

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TUPRB013

Simulation Studies for a EEHG seeded FEL in the XUV

laser, bunching, electron, FEL

1705

V. Grattoni, S. Ackermann, R.W. Aßmann, B. Faatz, T. Lang, C. Lechner, M.M. Mohammad Kazemi, G. Paraskaki, J. Zemella
DESY, Hamburg, Germany
W. Hillert
University of Hamburg, Institut für Experimentalphysik, Hamburg, Germany
S. Reiche
PSI, Villigen PSI, Switzerland

Echo-enabled harmonic generation (EEHG) is a promising technique for seeded free electron lasers (FELs) not only to go down to wavelengths of 4 nm, but also to simplify the schemes that are currently used to achieve a similar wavelength range (double cascade HGHG). Thus a study optimizing the EEHG performance in the wavelength range from 60 to §I{4}{nm} has been performed. The more critical working point, at 4 nm, is here analyzed in terms of seed laser energy stability for two different seed laser frequencies: visible and UV.

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reference for this paper ※ https://doi.org/10.18429/JACoW-IPAC2019-TUPRB013

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paper received ※ 30 April 2019 paper accepted ※ 23 May 2019 issue date ※ 21 June 2019

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TUPRB021

Undulator Radiation Dose Caused by Synchrotron Radiation at the European XFEL

undulator, radiation, FEL, vacuum

1724

S. Liu
DESY, Hamburg, Germany
Y. Li, F. Wolff-Fabris
EuXFEL, Hamburg, Germany

Radiation damage of the undulators is a big concern for the light sources. At the European XFEL (EuXFEL), dosimeters based on on-line Radfets are used for the un-dulator radiation dose measurements. However, since the Radfets are not only sensitive to the electrons and neu-trons but also to the photons, it can capture the synchro-tron radiation (SR) generated in the undulators, which is not considered to be the main source for undulator radia-tion damage. Therefore, it is important to estimate the contribution of synchrotron radiation to the radiation doses measured by the Radfets. For this purpose, we have first calculated the synchrotron radiation profile using SPECTRA, and then put the profile into the tracking code BDSIM to track it through the whole undulator beam line. The radiation doses from SR have been simulated and compared with the measured values. The differences in the radiation doses measured by the Radfets before and after Pb shielding will also be presented.

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reference for this paper ※ https://doi.org/10.18429/JACoW-IPAC2019-TUPRB021

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paper received ※ 30 April 2019 paper accepted ※ 22 May 2019 issue date ※ 21 June 2019

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TUPRB026

Optics & Compression Schemes for a Possible FLASH Upgrade

FEL, emittance, electron, laser

1744

J. Zemella, M. Vogt
DESY, Hamburg, Germany

The proposed FLASH upgrade will rely on high quality electron beams provided to all undulator beamlines. Here we describe possible modifications to the FLASH lattice and the compression scheme that aim at improving the beam quality and the ability to control critical beam properties along the machine - simultaneously and independently for all beamlines.

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reference for this paper ※ https://doi.org/10.18429/JACoW-IPAC2019-TUPRB026

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paper received ※ 11 April 2019 paper accepted ※ 22 May 2019 issue date ※ 21 June 2019

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TUPRB037

Experimental Demonstration of Vector Beam Generation With Tandem Helical Undulators

polarization, undulator, experiment, radiation

1766

S. Matsuba
HSRC, Higashi-Hiroshima, Japan
M. Fujimoto, M. Katoh
UVSOR, Okazaki, Japan
M. Hosaka
Nagoya University, Nagoya, Japan
K. Kawase
QST, Tokai, Japan
T. Konomi, N. Yamamoto
KEK, Ibaraki, Japan
A. Miyamoto
Toshiba, Yokohama, Japan
S. Sasaki
ANL, Argonne, Illinois, USA

Vector beam is a light beam with spatially modulated polarization state across the beam. Particular examples of vector beam are radial and azimuthal polarization which have donut-shaped intensity and radially and azimuthally oriented linear polarization state. Vector beam has long been interest in the laser community and it is well known that vector beam can be created by superposing two optical vortex beams which have spiral wave fronts. It has been demonstrated that optical vortex beam can be generated from a helical undulator as harmonics. Therefore, we propose a scheme to generate vector beam by superposing two optical vortex beams from two helical undulators in tandem, based on the principle of the ’crossed undulator’. The experiment was carried out at UVSOR BL1U. In this paper, we describe the principle and the experimental details.

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reference for this paper ※ https://doi.org/10.18429/JACoW-IPAC2019-TUPRB037

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paper received ※ 15 May 2019 paper accepted ※ 23 May 2019 issue date ※ 21 June 2019

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TUPRB041

Simulation of Short-Pulse Generation from a Dynamically Detuned IR-FEL Oscillator and Pulse Stacking at an External Cavity

FEL, cavity, electron, radiation

1778

Y. Sumitomo, Y. Hayakawa, T. Sakai
LEBRA, Funabashi, Japan
R. Hajima
QST, Tokai, Japan

Funding: Q-LEAP program supported by Ministry of Education, Culture, Sports, Science and Technology, Japan
At the LEBRA facility of Nihon U., we have an IR-FEL oscillator to generate radiations in the range of wavelengths 1-6 um for various experiments. A research program has been established to explore the application of the IR-FEL to generate attosecond UV and X-ray pulses through the high harmonic generation (HHG) in noble gases, where the IR-FEL pulses must have a high-peak power and a short-pulse duration. The property of generated FEL pulse is affected by the cavity length detuning of FEL oscillator as well as the small signal gain and the cavity loss. The operation at a small- or zero-detuning length is necessary to generate a FEL pulse shorter than the bunch length, although it requires a long macro-pulse to reach the saturation. For the short FEL pulse generation within a limited macro-pulse length at the LEBRA LINAC, we apply a dynamical modulation to the electron bunch repetition, that is equivalent to a dynamical detuning of the FEL cavity length. We illustrate the potential performance of the IR-FEL with the dynamical detuning by time-dependent 3D FEL simulations. We also evaluate the enhancement of the FEL pulses by an external cavity stacking for the sake of the HHG application.

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reference for this paper ※ https://doi.org/10.18429/JACoW-IPAC2019-TUPRB041

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paper received ※ 29 April 2019 paper accepted ※ 23 May 2019 issue date ※ 21 June 2019

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TUPRB046

Second Order Intensity Correlation and Statistical Properties of a Soft X-Ray Free Electron Laser

laser, FEL, radiation, electron

1788

C.L. Li, J.H. Chen, Z.C. Chen, X.T. Wang, H.L. Wu
SINAP, Shanghai, People’s Republic of China
B. Liu, T. Liu
SARI-CAS, Pudong, Shanghai, People’s Republic of China

High degree of transverse field coherence is one of the unique properties of an FEL compared with a 3rd gen-eration storage ring light source. As a result, the FEL advances the development of innovative research and technology that was not previously feasible. A truly coherent source should be coherent in all orders de-scribed from the intensity correlation functions. In this paper, second order intensity correlation of FEL radia-tion is investigated based on the Hanbury Brown-Twiss intensity correlation method. The statistical properties of radiation produced from SASE was also investigated and compared with the statistical proper-ties of a phase-locked laser. The results show that the statistical properties of a SASE mode behave as a cha-otic source, which is significantly different from the properties of a phase-locked laser beam.

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reference for this paper ※ https://doi.org/10.18429/JACoW-IPAC2019-TUPRB046

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paper received ※ 13 May 2019 paper accepted ※ 22 May 2019 issue date ※ 21 June 2019

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TUPRB069

Study of FEL Operation Using Collimator without X-band Linearizer in HX Line at PAL-XFEL

FEL, operation, electron, linac

1824

H. Yang, C.-K. Min, I.H. Nam
PAL, Pohang, Kyungbuk, Republic of Korea

Funding: This work is supported by MSIP, Korea.
A Hard X-ray (HX) line in PAL-XFEL consists of an e-gun, a Laser Heater (LH), S-band accelerators, an X-band LINearizer (XLIN), three Bunch Compressors (BC), a dog-leg, and an undulator line. It generates 2.5 - 15-keV FEL with over than 1-mJ pulse energy. The XLIN before BC1 is used for linearizing the energy chirp in the longitudinal phase space and provides the flexibility for FEL optimization and operation. However, it causes the instability of FEL by large jitters and drift because of higher frequency. We study the FEL operation without XLIN. The collimator in the center of BC1 is used removing the slices to cause nonlinear compression. We optimize the FEL by short electron bunch with under 30 fs. In this paper, we present details of the optimizing sequence and performance for the FEL operation without XLIN.

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reference for this paper ※ https://doi.org/10.18429/JACoW-IPAC2019-TUPRB069

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paper received ※ 13 May 2019 paper accepted ※ 23 May 2019 issue date ※ 21 June 2019

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TUPRB075

Higher Order Mode Spectra Study of 3.9 GHz Superconducting Radio Frequency Cavities for the European XFEL

cavity, HOM, electron, FEL

1840

L. Shi, S. Reiche
PSI, Villigen PSI, Switzerland
N. Baboi, A. Sulimov, E. Vogel, T. Wamsat
DESY, Hamburg, Germany
R.M. Jones, N.Y. Joshi
UMAN, Manchester, United Kingdom
P. Pierini
ESS, Lund, Sweden

Funding: The work is part of EuCARD2 and was partly funded by the European Commission, GA 312453.
It is important to verify both by simulation and experiments the wakefields in superconducting radio frequency (SRF) cavities, which can degrade the electron beam quality considerably or impose excessive heat load if left undamped. In this paper, we investigate the Higher Order Mode (HOM) spectra of the 3.9 GHz SRF cavities, which are assembled in a cryogenic module and are used to linearize the longitudinal phase space of the electron beam in the injector of the European XFEL. The HOM spectra are significantly different from the ones from a single cavity due to the coupling of the modes amongst cavities. The measurements not only provide direct input for the beam dynamics studies but also for the beam instrumentation utilizing these modes. The mode spectra are also investigated with a number of numerical simulations and the comparison with measurements shows favorable agreement.

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reference for this paper ※ https://doi.org/10.18429/JACoW-IPAC2019-TUPRB075

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paper received ※ 13 May 2019 paper accepted ※ 23 May 2019 issue date ※ 21 June 2019

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TUPRB084

High Level Software Development Framework and Activities on VELA/CLARA

controls, hardware, operation, interface

1855

D.J. Scott, A.D. Brynes, M.P. King
STFC/DL/ASTeC, Daresbury, Warrington, Cheshire, United Kingdom
A.D. Brynes, D.J. Scott
Cockcroft Institute, Warrington, Cheshire, United Kingdom

The success of modern particle accelerators depends on good high level software. Over the past few years an integrated framework has been developed to better connect machine physicists to VELA/CLARA at the STFC’s Daresbury laboratory. This framework is comprised of a number of tools, including, a c++/Python API to interface to the EPICS control system with which all High Level Software can be developed. The API is encapsulated, extensible and designed to grow as further Phases of CLARA are installed. The API is seamlessly integrated with the VELA/CLARA virtual accelerator and other activities by the simulations group. As well as presenting the design choices and methodology we will give an overview of the first control room applications built using our tools and how they will form the basis for a new programme of machine learning and optimisation on CLARA.

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reference for this paper ※ https://doi.org/10.18429/JACoW-IPAC2019-TUPRB084

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paper received ※ 14 May 2019 paper accepted ※ 21 May 2019 issue date ※ 21 June 2019

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TUPRB090

Preliminary Considerations of Atomic Inner-Shell X-Ray Laser for Self-Seeding at LCLS-II

FEL, photon, radiation, experiment

1871

A. Halavanau, C. Pellegrini, J. Wu
SLAC, Menlo Park, California, USA
A.I. Benediktovitch
EuXFEL, Hamburg, Germany
N. Rohringer
Max Planck Institute for the Physics of Complex Systems, Dresden, Germany

Funding: This work was supported by the U.S. Department of Energy Contract No. DE-AC02-76SF00515.
The atomic inner-shell X-ray lasing, induced by the irradiation of focused XFEL SASE pulses, was demonstrated in gases, liquid jets and solids. In this proceeding, we discuss the possible use of this concept in self-seeding scheme at LCLS-II. We provide a preliminary study of different lasing media and corresponding SASE XFEL parameters. For the case of noble gas inner-shell X-ray laser, we study the requirements for gas pressure and XFEL pulse focusing. Finally, we discuss possible designs of this system and its advantages in LCLS-II operations.

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reference for this paper ※ https://doi.org/10.18429/JACoW-IPAC2019-TUPRB090

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paper received ※ 13 May 2019 paper accepted ※ 22 May 2019 issue date ※ 21 June 2019

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TUPRB101

Damping Trapped Modes in an in-Vacuum Undulator at a Synchrotron Radiation Light Source

vacuum, damping, HOM, impedance

1895

K. Tian, Z. Li, A. Ringwall, J.J. Sebek
SLAC, Menlo Park, California, USA

Funding: Work supported by US Department of Energy Contract DE-AC03-76SF00515.
In this paper, we report the efforts in solving the problem of coupled-bunch instabilities caused by an in-vacuum undulator in the SPEAR3 storage ring. After exploring several approaches to reduce the strength of the trapped modes, we found that ferrite dampers were the most effective and simplest way for mode damping in our SPEAR3 in-vacuum undulator. The results of the first RF cold measurement on an in-vacuum undulator equipped with these ferrite dampers agree well with numerical simulations.

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reference for this paper ※ https://doi.org/10.18429/JACoW-IPAC2019-TUPRB101

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paper received ※ 13 May 2019 paper accepted ※ 20 May 2019 issue date ※ 21 June 2019

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TUPRB102

Numerical Study of the Delta II Polarizing Undulator for LCLS II

undulator, polarization, electron, laser

1899

K. Tian, H.-D. Nuhn
SLAC, Menlo Park, California, USA

Funding: Work supported by US Department of Energy Contract DE-AC03-76SF00515.
The Delta undulator has been operated successfully in LCLS with full control of the polarization mode and K value of the device. In LCLS II, a new Delta II undulator will be based on a similar design but with some differences. In this paper, we will present numerical simulation results that provide guidance to choose the geometric shape of the magnet poles and define the required tolerance for assembling the undulator magnets.

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reference for this paper ※ https://doi.org/10.18429/JACoW-IPAC2019-TUPRB102

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paper received ※ 10 May 2019 paper accepted ※ 20 May 2019 issue date ※ 21 June 2019

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TUPTS001

Improvements in Rf Multi Cusp Negative Ion Source

plasma, ion-source, coupling, operation

1928

A.M. George, M.P. Dehnel, S.V. Melanson, D.E. Potkins, T.M. Stewart
D-Pace, Nelson, British Columbia, Canada
N. Broderick
University of Auckland, Auckland, New Zealand
Y. Shimabukuro
Doshisha University, Graduate School of Engineering, Kyoto, Japan

D-Pace’s 13.56 MHz Radio Frequency (RF) multi cusp negative ion source uses an Aluminium Nitride (AlN) dielectric window for coupling RF power from an external antenna to the plasma chamber. Ion source operation was limited to low RF power (< 3500 W) due to failures (cracks) occurring on the window during experiments. Such events can cause damages to the vacuum system and plasma chamber. The current work deals with simulations performed on the ion source to study the factors leading to the failure of the window. Based on results from the simulations, a new design was introduced. The improved design yielded positive results in terms of source performance and stability of the AlN window.

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reference for this paper ※ https://doi.org/10.18429/JACoW-IPAC2019-TUPTS001

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paper received ※ 15 May 2019 paper accepted ※ 22 May 2019 issue date ※ 21 June 2019

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TUPTS007

SPIRAL2 RFQ Bunch Length and Longitudinal Emittance Measurements.

rfq, emittance, proton, linac

1944

G. Normand, M. Di Giacomo, R. Ferdinand, O. Kamalou, J.-M. Lagniel, A. Savalle
GANIL, Caen, France
D. Uriot
CEA-DRF-IRFU, France

The SPIRAL2 RFQ is designed to accelerate light and heavy ions up to A/Q=3 in CW mode to 0.75MeV/u. During its commissioning, the bunch lengths measured using a Beam Extension Monitor were compared with simulations for different ion species (Proton, Helium, Oxygen, Argon). The longitudinal emittances measured using the 3 gradients method and a multiparticule optimization method were also compared successfully to the expected ones.

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reference for this paper ※ https://doi.org/10.18429/JACoW-IPAC2019-TUPTS007

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paper received ※ 19 April 2019 paper accepted ※ 21 May 2019 issue date ※ 21 June 2019

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TUPTS012

Emittance Reduction of RF Photoinjector Generated Electron Beams By Transverse Laser Beam Shaping

laser, emittance, cathode, experiment

1958

M. Groß, P. Boonpornprasert, Y. Chen, J.D. Good, H. Huck, I.I. Isaev, C. Koschitzki, M. Krasilnikov, S. Lal, X. Li, O. Lishilin, G. Loisch, D. Melkumyan, S.K. Mohanty, R. Niemczyk, A. Oppelt, H.J. Qian, H. Shaker, G. Shu, F. Stephan, G. Vashchenko
DESY Zeuthen, Zeuthen, Germany
I. Will
MBI, Berlin, Germany

Laser pulse shaping is one of the key elements to generate low emittance electron beams with RF photoinjectors. Ultimately high performance can be achieved with ellipsoidal laser pulses, but 3-dimensional shaping is challenging. High beam quality can also be reached by simple transverse pulse shaping, which has demonstrated improved beam emittance compared to a transversely uniform laser in the ‘pancake’ photoemission regime. In this contribution we present the truncation of a Gaussian laser at a radius of approximately one σ in the intermediate (electron bunch length directly after emission about the same as radius) photoemission regime with high acceleration gradients (up to 60 MV/m). This type of electron bunch is used e.g. at the European XFEL and FLASH free electron lasers at DESY, Hamburg site and is being investigated in detail at the Photoinjector Test facility at DESY in Zeuthen (PITZ). Here we present ray-tracing simulations and experimental data of a laser beamline upgrade enabling variable transverse truncation. Initial projected emittance measurements taken with help of this setup are shown, as well as supporting beam dynamics simulations. Additional simulations show the potential for substantial reduction of slice emittance at PITZ.

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reference for this paper ※ https://doi.org/10.18429/JACoW-IPAC2019-TUPTS012

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paper received ※ 24 April 2019 paper accepted ※ 18 May 2019 issue date ※ 21 June 2019

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TUPTS014

SINGLE SHOT CATHODE TRANSVERSE MOMENTUM IMAGING IN PHOTOINJECTORS

cathode, solenoid, emittance, electron

1964

P.W. Huang, Y. Chen, J.D. Good, M. Groß, I.I. Isaev, C. Koschitzki, M. Krasilnikov, S. Lal, X. Li, O. Lishilin, D. Melkumyan, R. Niemczyk, A. Oppelt, H.J. Qian, H. Shaker, F. Stephan, G. Vashchenko
DESY Zeuthen, Zeuthen, Germany
D. Filippetto, F. Sannibale
LBNL, Berkeley, California, USA
C.-X. Tang
TUB, Beijing, People’s Republic of China
W. Wan
ShanghaiTech University, Shanghai, People’s Republic of China

In state of the art photoinjector electron sources, cathode performance determines the lower limit of achievable beam emittance. Measuring the thermal emittance at the photocathodes in electron guns is of vital importance for improving the injectors. Traditional methods, like solenoid scan, pepper-pot, need multi-shots and are time-consuming, therefore suffer from machine stability. Here we propose a new method, named cathode transverse momentum imaging. By tuning the gun solenoid focusing, the electrons’ transverse momentum at the cathode is imaged to a downstream screen, which enables a single shot measurement. Several experiments have been done at the Photo Injector Test Facility at DESY in Zeuthen (PITZ) with a Cs2Te cathode. Measurements of cathode transverse momentum, the corresponding spectra, cathode transverse momentum map and its correlation with surface electric field are presented.

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reference for this paper ※ https://doi.org/10.18429/JACoW-IPAC2019-TUPTS014

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paper received ※ 14 May 2019 paper accepted ※ 22 May 2019 issue date ※ 21 June 2019

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TUPTS021

Basic Design of the RF Power System for IRANCYC-10 Accelerator

cyclotron, ISOL, vacuum, operation

1972

M. Dehghan, F. Abbasi
Shahid Beheshti University, Tehran, Iran
H. Azizi
ILSF, Tehran, Iran
F. Ghasemi
NSTRI, Tehran, Iran
A. Taghibi Khotbeh-Sara
KNTU, Tehran, Iran

In this paper the basic design of an RF system to produce the required power of IRANCYC-10 cyclotron accelerator is reported. The designed system can generate 15 kW power at the operating frequency of 71 MHz CW. The authors provide a step-by-step ex-planation of the process of the design. It is carried out in three sections; (1) RF design features of the acceler-ator is investigated and power value is calculated in accordance with the requirements of the cyclotron, (2) the choice of solid state amplifiers as the RF power source is presented with its available power and struc-ture, (3) design of insertion instruments is reported to transfer and combine the RF power. The purpose of the paper is to achieve the best performance of the RF system, as well as decreasing overall size by using modular devices.

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reference for this paper ※ https://doi.org/10.18429/JACoW-IPAC2019-TUPTS021

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paper received ※ 15 May 2019 paper accepted ※ 20 May 2019 issue date ※ 21 June 2019

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TUPTS023

A CENTRAL REGION UPGRADE OF THE k800 SUPERCONDUCTING CYCLOTRON AT INFN-LNS

cyclotron, extraction, injection, acceleration

1975

G. D’Agostino, L. Calabretta, D. Rifuggiato
INFN/LNS, Catania, Italy
W.J.G.M. Kleeven
IBA, Louvain-la-Neuve, Belgium

The Superconducting Cyclotron (CS) at INFN-LNS in Catania is currently under an upgrade process. The plan is to deliver beams of ions with mass number 𝐴 ≤ 40 with power up to 10 kW. This ambitious goal can be achieved increasing the efficiency of the injection and extraction processes. An extraction efficiency close to 100% is expected by extracting the specific ion beams from the CS by stripping and no longer by electrostatic deflectors. The beams are injected axially and bent onto the median plane with a spiral inflector. Currently, the injection efficiency stays around 15%, also including the effect of a drift buncher placed in the axial injection line. In order to increase the injection efficiency, the study of an upgraded CS central region is ongoing at INFN-LNS. In this paper, the results of simulations of beam tracking through the cyclotron axial bore, the spiral inflector, the central region and further up to the extraction system are presented.

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reference for this paper ※ https://doi.org/10.18429/JACoW-IPAC2019-TUPTS023

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paper received ※ 29 April 2019 paper accepted ※ 21 May 2019 issue date ※ 21 June 2019

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TUPTS033

J-PARC RCS: High-Order Field Components Inherent in the Injection Bump Magnets and Their Effects on the Circulating Beam During Multi-Turn Injection

injection, resonance, sextupole, operation

2009

H. Hotchi, H. Harada, T. Takayanagi
JAEA/J-PARC, Tokai-mura, Japan

The J-PARC RCS utilizes four sets of pulsed dipole magnets for the formation of injection orbit bump. The injection bump magnets have a large aspect ratio (gap length/core length), so there are other high-order field components inherent in their magnetic fields in addition to the main dipole component. The high-order field components, which locally exist in the injection section not following the lattice super-periodicity, have a significant influence on the circulating beam during multi-turn injection via the excitation of high-order random betatron resonances. This paper discusses the detailed mechanism of emittance growth and beam loss caused by the high-order field components of the injection bump magnets including its correction scenario on the basis of numerical simulation and experimental results.

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reference for this paper ※ https://doi.org/10.18429/JACoW-IPAC2019-TUPTS033

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paper received ※ 18 April 2019 paper accepted ※ 23 May 2019 issue date ※ 21 June 2019

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TUPTS045

Simulation Analysis of LLRF Feedforward Compensation to Beam Loading for CiADS LINAC

cavity, beam-loading, controls, feedback

2027

X.C. Xu, J.Y. Ma
IMP/CAS, Lanzhou, People’s Republic of China

A simulation is coded to calculate the beam loading in the cavity of CiADS and the response of the LLRF system. In the pulse operating mode, the fluctuation of amplitude and phase of the cavity field contributed by the transient beam loading is traced. During the simulation the effect of beam current fluctuation, and timing jitter were determined. The deviation margin of relational parameters is lined out to meet the requirement for cavity stability with amplitude 0.1% and phase 0.1°.

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reference for this paper ※ https://doi.org/10.18429/JACoW-IPAC2019-TUPTS045

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paper received ※ 15 May 2019 paper accepted ※ 21 May 2019 issue date ※ 21 June 2019

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TUPTS048

Preliminary Study on the Injection System Upgrade for CSNS-II

injection, linac, power-supply, neutron

2037

S. Wang, M.Y. Huang, S.Y. Xu
IHEP, Beijing, People’s Republic of China

Funding: Work supported by National Natural Science Foundation of China (Project No. U1832210)
The first phase of the China Spallation Neutron Source (CSNS-I) had completed the national acceptance in August, 2018. The physics design of the second phase (CSNS-II) has already begun. The CSNS-II accelerator upgrade contains three main components, including the Linac energy upgrade from 80 MeV to 300 MeV, injection system upgrade, and new Magnetic Alloy dual-harmonic cavity. In this paper, a preliminary study on the injection system upgrade had been done. A preliminary upgrade scheme for the injection system would be given. Furthermore, some preliminary simulation and calculation for the upgrade injection system had been carried out. The analysis results showed that most injection parameters can preliminarily meet the requirements of accelerator power upgrade.

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reference for this paper ※ https://doi.org/10.18429/JACoW-IPAC2019-TUPTS048

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paper received ※ 15 May 2019 paper accepted ※ 23 May 2019 issue date ※ 21 June 2019

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TUPTS053

Design of a 217 MHz VHF Gun at Tsinghua University

gun, cathode, electron, cavity

2050

L.M. Zheng, H. Chen, Y.C. Du, W.-H. Huang, R.K. Li, Z.Z. Li, C.-X. Tang
TUB, Beijing, People’s Republic of China
B. Gao
IHEP, Beijing, People’s Republic of China

A 217 MHz VHF gun operating in CW mode is designing at Tsinghua University. The cathode gradient is designed to be 30 MV/m to accelerate the electron bunches up to 878 keV. The cavity profile is optimized in CST to minimize the input power, peak surface electric field, and peak wall power density. The multipacting analysis and the thermal analysis are also presented in this paper. Further gun shape optimization and mechanical design are ongoing.

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reference for this paper ※ https://doi.org/10.18429/JACoW-IPAC2019-TUPTS053

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paper received ※ 15 May 2019 paper accepted ※ 18 May 2019 issue date ※ 21 June 2019

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TUPTS059

Conceptual Design of the SC230 Superconducting Cyclotron for Proton Therapy

cyclotron, cavity, proton, acceleration

2058

O. Karamyshev, S. Gurskiy, G.A. Karamysheva, D.V. Popov, G. Shirkov, S.G. Shirkov, V.L. Smirnov, S.B. Vorozhtsov
JINR, Dubna, Moscow Region, Russia

Physical design of the compact superconducting cyclotron SC230 (91.5MHz) has been performed. The cyclotron will deliver up to 230 MeV beam for proton therapy and medico-biological research. We have performed simulations of magnetic and accelerating systems of the SC230 cyclotron and specified the main parameters of the accelerator.

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reference for this paper ※ https://doi.org/10.18429/JACoW-IPAC2019-TUPTS059

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paper received ※ 15 May 2019 paper accepted ※ 21 May 2019 issue date ※ 21 June 2019

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TUPTS060

Beam Dynamics Simulations in the Dubna SC230 Superconducting Cyclotron for Proton Therapy

extraction, cyclotron, acceleration, proton

2061

G.A. Karamysheva, S. Gurskiy, O. Karamyshev, D.V. Popov, G. Shirkov, S.G. Shirkov, V.L. Smirnov, S.B. Vorozhtsov
JINR, Dubna, Moscow Region, Russia
V. Malinin
JINR/DLNP, Dubna, Moscow region, Russia

We present results of the beam dynamics simulation for the compact isochronous superconducting cyclotron SC230. We have performed beam tracking starting from the ion source. The extraction system scheme and results of beam extraction simulations are presented. The codes and methods used for beam tracking are briefly described.

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reference for this paper ※ https://doi.org/10.18429/JACoW-IPAC2019-TUPTS060

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paper received ※ 15 May 2019 paper accepted ※ 20 May 2019 issue date ※ 21 June 2019

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TUPTS073

Analysis of Electron Beam Divergence in Diamond Field Emitter Array Cathodes

cathode, focusing, experiment, electron

2090

D. Kim, H.L. Andrews, R.L. Fleming, C. Huang, J.W. Lewellen, K.E. Nichols, V.N. Pavlenko, E.I. Simakov
LANL, Los Alamos, New Mexico, USA
B.K. Choi
Cheju Halla University, Jeju-si, Republic of Korea

Funding: Los Alamos National Laboratory (LANL) Laboratory Directed Research and Development (LDRD) program (Contract DE-AC52-06NA25396) and Sandia National Laboratories (Contract DE-NA-0003525).
At Los Alamos National Laboratory (LANL), we have recently established a capability to fabricate diamond array cathodes for electron beam sources. Our fabricated diamond field emitter arrays (DFEAs) are the arrays of micrometer-scale diamond pyramids with nanometer-scale sharp tips and produce high per-tip current (> 15 μA per-tip) in DC testing. For the beam divergence measurements, we designed and assembled a test stand consisting of a DFEA cathode, a mesh aperture of 0.375-inch for an anode, and AZO (ZnO:Al2O3) screen coated on a sapphire substrate for beam visualization. A negative voltage of about 40 kV is applied to the cathode, and the mesh and the screen are kept at ground. We measure a size of the electron beam on the AZO screen at different mesh to screen distances at a fixed cathode-mesh gap in order to calculate the beam divergence angles. We also perform the beam dynamics simulations with Computer Simulation Technology (CST) Studio and General Particle Tracer (GPT) using a single pyramidal shape with a nanowire tip model. In this presentation, the measured experimental results of the beam divergences will be compared to the beam dynamic simulations.

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reference for this paper ※ https://doi.org/10.18429/JACoW-IPAC2019-TUPTS073

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paper received ※ 14 May 2019 paper accepted ※ 21 May 2019 issue date ※ 21 June 2019

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TUPTS078

Coherent Electron Cooling (CeC) Experiment at RHIC: Status and Plans

electron, FEL, experiment, SRF

2101

V. Litvinenko, K. Mihara
Stony Brook University, Stony Brook, USA
Z. Altinbas, J.C. Brutus, A. Di Lieto, D.M. Gassner, T. Hayes, P. Inacker, J.P. Jamilkowski, Y.C. Jing, R. Kellermann, J. Ma, G.J. Mahler, M. Mapes, R.J. Michnoff, T.A. Miller, M.G. Minty, G. Narayan, M.C. Paniccia, D. Phillips, I. Pinayev, S.K. Seberg, F. Severino, J. Skaritka, L. Smart, K.S. Smith, Z. Sorrell, R. Than, J.E. Tuozzolo, E. Wang, G. Wang, Y.H. Wu, B.P. Xiao, T. Xin, A. Zaltsman
BNL, Upton, Long Island, New York, USA
I. Petrushina
SUNY SB, Stony Brook, New York, USA
K. Shih
SBU, Stony Brook, New York, USA

Funding: Work supported by Brookhaven Science Associates, LLC under Contract No. DE-AC02-98CH10886 with the U.S. Department of Energy and NSF Grant No. PHY-141525
We will present currents status of the CeC experiment at RHIC and discuss plans for future. Special focus will be given to unexpected experimental results obtained during RHIC Run 18 and discovery of a previously unknown type of microwave instability. We called this new phenomenon micro-bunching Plasma Cascade Instability (PCI). Our plan for future experiments includes suppressing this instability in the CeC accelerator and using it as a broad-band amplifier in the CeC system.

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reference for this paper ※ https://doi.org/10.18429/JACoW-IPAC2019-TUPTS078

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paper received ※ 19 May 2019 paper accepted ※ 22 May 2019 issue date ※ 21 June 2019

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TUPTS083

Simulations and Experimental Plans for a High-Repetition-Rate Field-Enhanced Conduction-Cooled Superconducting RF Electron Source

cavity, electron, cathode, SRF

2113

O. Mohsen, A. McKeown, D. Mihalcea, P. Piot, I. Salehinia
Northern Illinois University, DeKalb, Illinois, USA
R. Dhuley, M.G. Geelhoed, D. Mihalcea, P. Piot, J.C.T. Thangaraj
Fermilab, Batavia, Illinois, USA

Funding: Work supported by DOE awards DE-SC0018367 with NIU and DE-AC02-07CH11359 with Fermilab.
We present a novel RF design for a field enhanced electron source driven by field emission cathodes. The proposed electron source relies on the enhanced high electric field gradients at the cathode to simultaneously extract and accelerate electrons. The system will be tested in a conduction-cooled superconducting radio-frequency cavity recently demonstrated at Fermilab. In this paper, we present electromagnetic and thermal simulations of the setup that support the feasibility of the design.

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reference for this paper ※ https://doi.org/10.18429/JACoW-IPAC2019-TUPTS083

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paper received ※ 18 May 2019 paper accepted ※ 23 May 2019 issue date ※ 21 June 2019

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TUPTS084

Performances of Silicon-Based Field-Emission Cathodes Coated with UltraNano Crystalline Diamond

cathode, electron, experiment, vacuum

2117

O. Mohsen, V. Korampally, A. Lueangaramwong, P. Piot, V. Valluri
Northern Illinois University, DeKalb, Illinois, USA
R. Divan, A.V. Sumant
Argonne National Laboratory, Argonne, Illinois, USA
P. Piot
Fermilab, Batavia, Illinois, USA

Funding: Work supported by NSF grant PHY-1535401 and DOE award DE-SC0018367 with NIU
Field-emission electron sources have been considered as possible candidates for the production of bright or high-current electron bunches. In this paper, we report on the experimental characterization of silicon-based field-emitter arrays (FEA) in a DC high voltage gap. The silicon cathodes are produced via a simple self-assembling process. The measurement reported in this paper especially compares the field-emission properties of a nanostructured and planar diamond-coated Si-based cathode.

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reference for this paper ※ https://doi.org/10.18429/JACoW-IPAC2019-TUPTS084

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paper received ※ 17 May 2019 paper accepted ※ 23 May 2019 issue date ※ 21 June 2019

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TUPTS085

Design Study of 3.6-cell C-band Photocathode Electron Gun

gun, emittance, FEL, cathode

2121

W. Fang, Z.T. Zhao
SSRF, Shanghai, People’s Republic of China
L. Wang
University of Chinese Academy of Sciences, Beijing, People’s Republic of China
L. Wang
SINAP, Shanghai, People’s Republic of China

A C-band photocathode injector composed of a 3.6-cell C-band photocathode RF gun and two 1.8-meter C-band accelerating structures is proposed. The injector is a low emittance electron source for Free Electron Lasers (FEL) and other compact light sources. The RF structure of the cavities is designed with 2D SUPERFISH simulation. The Beam dynamic study in ASTRA helps rectify the 2D RF simulation. To feed the cavities, a design of extra coaxial coupler with RF gun structure is presented. With compact focusing solenoids, for 0.25nC bunch charge, the final energy can reach 6.9 MeV energy and the 95% emittance can be as low as 0.23 mm mrad (95%). All the details of RF design and beam dynamics studies are presented in this paper.

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reference for this paper ※ https://doi.org/10.18429/JACoW-IPAC2019-TUPTS085

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paper received ※ 15 May 2019 paper accepted ※ 18 May 2019 issue date ※ 21 June 2019

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TUPTS091

Physics of Electron Beam Generation and Dynamics From Diamond Field Emitter Arrays

electron, cathode, ECR, experiment

2137

C. Huang, H.L. Andrews, R.C. Baker, R.L. Fleming, D. Kim, T.J. Kwan, V.N. Pavlenko, A. Piryatinski, E.I. Simakov
LANL, Los Alamos, New Mexico, USA

Funding: Work supported by the LDRD program at Los Alamos National Laboratory
Many applications such as compact accelerators and electron microscopy demand high brightness electron beams with small beam size and low emittance. Electric-field-assisted diamond emitters manufactured from semiconductor processes are strong candidates for cathodes in such sources. The micro-scale pyramid structure of the emitter has the desirable attribute of significant field enhancement at the sharp interfaces (apex and edges) to facilitate electron emission. We use the LSP particle-in-cell code to simulate the diamond emitter in a diode setup and obtain the beam size and divergence. An empirical fit of the fields around the apex is extracted for detail study. The trend of the beam divergence observed in the simulation is further corroborated using electron’s trajectory in the empirical field model.

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reference for this paper ※ https://doi.org/10.18429/JACoW-IPAC2019-TUPTS091

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paper received ※ 15 May 2019 paper accepted ※ 21 May 2019 issue date ※ 21 June 2019

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TUPTS093

Magnetized Gridded Thermionic Electron Source

electron, gun, cathode, emittance

2140

M.S. Stefani
ODU, Norfolk, Virginia, USA
C.M. Gulliford, V.O. Kostroun, C.E. Mayes, K.W. Smolenski
Cornell University (CLASSE), Cornell Laboratory for Accelerator-Based Sciences and Education, Ithaca, New York, USA
F.E. Hannon, M. Poelker, R. Suleiman
JLab, Newport News, Virginia, USA

Funding: This manuscript has been authored by Jefferson Science Associates, LLC under Contract No. DE-AC05-06OR23177 with the U.S. Department of Energy.
The study of magnetized electron beam has become a high priority for its use in ion beam cooling as part of Electron Ion Colliders and the potential of easily forming flat beams for various applications. The demand for high average current for effective ion beam cooling has caused consideration of using bunched magnetized electron beam produced by a gridded thermionic electron gun. This paper presents the design of a potential electron source for JCIEC first measurements characterizing the beam properties of a magnetized thermionic gun.

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reference for this paper ※ https://doi.org/10.18429/JACoW-IPAC2019-TUPTS093

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paper received ※ 15 May 2019 paper accepted ※ 21 May 2019 issue date ※ 21 June 2019

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TUPTS095

Global Model of Multi-Chamber Negative Hydrogen Ion Sources with Updated Hydrogen Plasma Chemistry

plasma, ion-source, electron, interface

2144

S.N. Averkin, S.A. Veitzer
Tech-X, Boulder, Colorado, USA

Funding: This work was performed under the auspices of the Department of Energy, Office of Basic Energy Sciences Award #DE-SC0009585.
Global models of plasma discharges are used to calculate volume averaged number densities and temperatures of plasma components. The wall fluxes are estimated based on heuristic expressions that "patch" together analytic and semi-analytic solutions covering from low-pressure to high-pressure regimes. Due to the nature of the wall fluxes estimation, the global models are limited to single chamber designs. We present the extension of the Global Enhanced Vibrational Kinetic Model (GEVKM) * for the multi-chamber design with the updated hydrogen plasma chemistry **. The extended GEVKM consists of separate global models for macroscopic parameters of all species in each chamber coupled through interface boundary conditions. We compare our model with fluid simulation results for a plasma composition and species temperatures in the negative hydrogen ion source developed at IPP Garching.
* Averkin S.N. et al, IEEE Trans. Plasma Sci., Vol. 43, N. 6, pp. 1926-1943, 2015.
** Yang W. et al, Phys. Plasmas, 25, 113509, 2018.

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reference for this paper ※ https://doi.org/10.18429/JACoW-IPAC2019-TUPTS095

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paper received ※ 21 May 2019 paper accepted ※ 23 May 2019 issue date ※ 21 June 2019

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TUPTS096

Fluid Models of Inductively Coupled Plasma Sources for Negative Hydrogen Ion Sources

plasma, electron, ion-source, neutron

2147

S.A. Veitzer, P. Stoltz
Tech-X, Boulder, Colorado, USA

Funding: This work was performed under the auspices of the Department of Energy, Office of Basic Energy Sciences Award #DE-SC0009585.
Negative hydrogen ion sources are widely used to produce neutron beams via spallation both for neutron science in its own right, and as neutron sources for fusion devices. Numerical modeling is a useful tool for trying to optimize negative hydrogen ion sources. However there are significant numerical and computational challenges that have to be overcome, including code performance and resolution of separation of time scales between ion and electron motions. One method is to utilize fluid models to simulate inductively coupled ion sources (ICPs). We have been developing algorithms to simulate negative hydrogen production in high-power, external-antenna ICP sources. We present simulation results using the USim*,** framework to model plasma chemistry that produces negative hydrogen, and model the effects of electron temperature on overall production rates. The numerical plasma chemistry models include processes of ionization, dissociation, recombination, as well as reactive dissociation of vibrationally resolved states and de-excitation of atomic hydrogen. We benchmark our plasma chemistry model results using plasma parameters relevant to experiments being carried out at the D-Pace Ion Source Test Facility. We have also been developing fluid-based drift/diffusion models for multi-component plasmas, such as those in negative hydrogen sources. These simulation results demonstrate enhancement of the effective diffusion rates in plasmas that contain both electrons and negative ions.
* J. Loverich and A. Hakim, J. Fusion Sci., 29(6), 2010.
** J. Loverich et al., AIAA, Vol. 4012, 2011.

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reference for this paper ※ https://doi.org/10.18429/JACoW-IPAC2019-TUPTS096

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paper received ※ 19 May 2019 paper accepted ※ 21 May 2019 issue date ※ 21 June 2019

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TUPTS104

Spatio-Temporal Shaping of the Photocathode Laser Pulse for Low-Emittance Shaped Electron Bunches

laser, electron, cathode, emittance

2163

T. Xu, P. Piot
Northern Illinois University, DeKalb, Illinois, USA
C.-J. Jing, A. Kanareykin
Euclid TechLabs, LLC, Solon, Ohio, USA
P. Piot
Fermilab, Batavia, Illinois, USA
J.G. Power
ANL, Argonne, Illinois, USA

Funding: This work is supported by the U.S. DOE contract No. DE- SC0017750 with Euclid Techlabs LLC., No. DE-SC0018656 with NIU, and No. DE-AC02-06CH11357 with ANL.
Photocathode laser shaping techniques to generate temporally shaped electron bunches are appealing owing to their simplicity. Such technique is being considered to form shaped electron bunches to enhance the transformer ratio in beam-driven accelerators. At low energy (i.e. during the emission process) the transverse and longitudinal space charge effects are coupled so that attaining a low beam transverse emittance require the laser to be spatiotemporal shaped. In this paper, we explore the generation of a linearly-ramped bunch with optimized transverse emittance by temporally and radially shaping the laser pulse to provide an adequate initial distribution. We discuss a possible implementation of the optical shaping technique and describe a planned experiment.

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reference for this paper ※ https://doi.org/10.18429/JACoW-IPAC2019-TUPTS104

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paper received ※ 14 May 2019 paper accepted ※ 23 May 2019 issue date ※ 21 June 2019

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TUPTS108

Numerical Simulations of RHIC FY17 Spin Flipper Experiments

resonance, experiment, dipole, polarization

2174

P. Adams, H. Huang, J. Kewisch, C. Liu, F. Méot, P. Oddo, V. Ptitsyn, V.H. Ranjbar, G. Robert-Demolaize, T. Roser
BNL, Upton, Long Island, New York, USA

Funding: Work supported by Brookhaven Science Associates, LLC under Contract No. DE-AC02-98CH10886 with the U.S. Department of Energy.
Spin flipper experiments during RHIC Run 17 have demonstrated the 97% effectiveness of polarization sign reversal during stores. Zgoubi numerical simulations were setup to reproduce the experimental conditions. A very good agreement between the experimental measurements and simulation results was achieved at 23.8GeV, thus the simulations are being used to help optimize the various Spin Flipper parameters. The ultimate goal for these simulations is to serve as guidance towards a perfect flip at high energies to allow a routine Spin Flipper use during physics runs.

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reference for this paper ※ https://doi.org/10.18429/JACoW-IPAC2019-TUPTS108

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paper received ※ 13 May 2019 paper accepted ※ 21 May 2019 issue date ※ 21 June 2019

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TUPTS110

Scanning the AC Dipole Resonance Proximity Parameter in the AGS Booster

dipole, resonance, booster, betatron

2179

K. Hock, H. Huang, F. Méot, P. Oddo, N. Tsoupas
BNL, Upton, Long Island, New York, USA

Funding: Work supported by Brookhaven Science Associates, LLC under Contract No. DE-SC0012704 with the U.S. Department of Energy.
An ac dipole system is installed in the AGS Booster in view of acceleration of polarized helion for RHIC and the eRHIC EIC. The amplitude of the vertical coherent oscillations induced by the ac dipole depends greatly on the resonance proximity parameter, δm, which is the distance between resonance tune and driving tune. Due to the non-zero momentum spread, particles with different momenta will have different value of δm. The rapid acceleration rate of the booster would cause δm to sweep, the amount of which would depend on the energy and the duration of the ac dipole cycle. These effects are simulated using zgoubi, which set a range of δm values suitable for both high spin flip efficiency and minimizing emittance growth, and the results of the simulations are discussed.

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reference for this paper ※ https://doi.org/10.18429/JACoW-IPAC2019-TUPTS110

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paper received ※ 12 May 2019 paper accepted ※ 22 May 2019 issue date ※ 21 June 2019

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WEYPLS1

Building the Impedance Model of a Real Machine

impedance, wakefield, coupling, cavity

2249

B. Salvant, D. Amorim, S.A. Antipov, S. Arsenyev, M.S. Beck, N. Biancacci, O.S. Brüning, J.V. Campelo, E. Carideo, F. Caspers, A. Farricker, A. Grudiev, T. Kaltenbacher, E. Koukovini-Platia, P. Kramer, A. Lasheen, M. Migliorati, N. Mounet, E. Métral, N. Nasr Esfahani, S. Persichelli, B.K. Popovic, T.L. Rijoff, G. Rumolo, E.N. Shaposhnikova, V.G. Vaccaro, C. Vollinger, N. Wang, C. Zannini, B. Zotter
CERN, Geneva, Switzerland
D. Amorim
Grenoble-INP Phelma, Grenoble, France
T. Dalascu
EPFL, Lausanne, Switzerland
M. Migliorati
Sapienza University of Rome, Rome, Italy
R. Nagaoka
SOLEIL, Gif-sur-Yvette, France
V.V. Smaluk
BNL, Upton, Long Island, New York, USA
B. Spataro
INFN/LNF, Frascati, Italy
N. Wang
IHEP, Beijing, People’s Republic of China
S.M. White
ESRF, Grenoble, France

A reliable impedance model of a particle accelerator can be built by combining the beam coupling impedances of all the components. This is a necessary step to be able to evaluate the machine performance limitations, identify the main contributors in case an impedance reduction is required, and study the interaction with other mechanisms such as optics nonlinearities, transverse damper, noise, space charge, electron cloud, beam-beam (in a collider). The main phases to create a realistic impedance model, and verify it experimentally, will be reviewed, highlighting the main challenges. Some examples will be presented revealing the levels of precision of machine impedance models that have been achieved.

Slides WEYPLS1 [5.648 MB]

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reference for this paper ※ https://doi.org/10.18429/JACoW-IPAC2019-WEYPLS1

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paper received ※ 10 May 2019 paper accepted ※ 23 May 2019 issue date ※ 21 June 2019

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WEYYPLM3

First Results of the Compensation of the Beam-Beam Effect with DC Wires in the LHC

experiment, beam-beam-effects, operation, collider

2262

G. Sterbini, D. Amorim, H. Bartosik, A. Bertarelli, R. Bruce, X. Buffat, F. Carra, L.R. Carver, G. Cattenoz, E. Effinger, S.D. Fartoukh, N. Fuster-Martínez, M. Gąsior, M. Gonzalez-Berges, A.A. Gorzawski, G.H. Hemelsoet, M. Hostettler, G. Iadarola, O.R. Jones, N. Karastathis, S. Kostoglou, I. Lamas Garcia, T.E. Levens, L.E. Medina Medrano, D. Mirarchi, J. Olexa, S. Papadopoulou, Y. Papaphilippou, D. Pellegrini, M. Pojer, L. Ponce, A. Poyet, S. Redaelli, A. Rossi, B. Salvachua, H. Schmickler, F. Schmidt, K. Skoufaris, M. Solfaroli, R. Tomás, G. Trad, D. Valuch, C. Xu, C. Zamantzas, P. Zisopoulos
CERN, Geneva, Switzerland
D. Amorim
Grenoble-INP Phelma, Grenoble, France
M. Fitterer, A. Valishev
Fermilab, Batavia, Illinois, USA
D. Kaltchev
TRIUMF, Vancouver, Canada
S. Kostoglou
National Technical University of Athens, Zografou, Greece
A.E. Levichev
BINP SB RAS, Novosibirsk, Russia
A. Poyet
Université Grenoble Alpes, Grenoble, France

The compensation of the long-range beam-beam interactions using DC wires is presently under study as an option for enhancing the machine performance in the frame of the High-Luminosity LHC project (HL-LHC). The original idea dates back more than 15 years. After the installation of four wire prototypes in the LHC in 2018, a successful experimental campaign was performed during the last months. The experimental setup and the main results are reported in this paper.

Slides WEYYPLM3 [6.371 MB]

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paper received ※ 06 May 2019 paper accepted ※ 22 May 2019 issue date ※ 21 June 2019

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WEYYPLS3

Development of Methods for Calculation of Bunch Radiation in Presence of Dielectric Objects

radiation, target, vacuum, focusing

2274

A.V. Tyukhtin, E.S. Belonogaya, S.N. Galyamin, V.V. Vorobev
Saint Petersburg State University, Saint Petersburg, Russia

Funding: This work was supported by the Russian Science Foundation (Grant # 18-72-10137).
Radiation of charged particles moving in presence of dielectric targets is of interests for various applications in accelerator and beam physics*. Typically, the size of the target is much larger than the wavelengths under consideration. This fact gives us an obvious small parameter of the problem and allows developing approximate methods of analysis. We develop two methods: "ray-optical method" and "aperture method"**. These methods can be very effective for all situations where we can find the tangential field components on the "aperture" which is an object boundary illuminated by Cherenkov radiation. We apply the aperture method to different dielectric objects including a prism, a cone, and a ball. Electromagnetic field is analyzed on different distances from the objects. The special attention is given to investigation of the field in the far-field (Fraunhofer) area having large importance for various applications. We obtain analytical results for different objects, demonstrate typical radiation patterns and discuss new physical effects, in particular, the phenomenon of concentration of radiation and effect of "Cherenkov spotlight". Prospects of use of aperture method and ray-optical one for other objects are discussed as well.
* R.Kieffer et al, PRL, 121, 054802 (2018).
** E.S.Belonogaya et al, JOSA B, 32, 649 (2015); S.N.Galyamin, A.V.Tyukhtin, PRL, 113, 064802 (2014); A.V.Tyukhtin et al, J. Instrum., 13, C02033 (2018).

Slides WEYYPLS3 [4.063 MB]

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reference for this paper ※ https://doi.org/10.18429/JACoW-IPAC2019-WEYYPLS3

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paper received ※ 14 May 2019 paper accepted ※ 20 May 2019 issue date ※ 21 June 2019

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WEZZPLS3

Longitudinal-Phase-Space Manipulation for Efficient Beam-Driven Structure Wakefield Acceleration

wakefield, linac, electron, acceleration

2296

W.H. Tan, P. Piot
Northern Illinois University, DeKalb, Illinois, USA
P. Piot
Fermilab, Batavia, Illinois, USA
A. Zholents, A. Zholents
ANL, Argonne, Illinois, USA

Funding: This work is funded by the United States Department of Energy awards DE-SC0018656 with Northern Illinois University and DE-AC02-06CH11357 with Argonne National Laboratory.
Collinear beam-driven structure wakefield acceleration (SWFA) is an advanced acceleration technique that could support the compact generation of high-energy beams for future multi-user x-ray free-electron-laser facilities*. Producing an ideal shaped drive beam through phase space manipulation is crucial for an efficient SWFA. Controlling the final longitudinal-phase space of the drive beam necessitate staged beam manipulations during acceleration. This paper describes the preliminary design of an accelerator beamline capable of producing drive beam with tailored current distribution and longitudinal-phase-space correlation. The proposed design is based on simple analytical models combined in a 1-D longitudinal beam-dynamics simulation tracking program supporting forward and backward (time reversal) tracking.
* A. Zholents, et al., Dielectric wakefield accelerator to drive the future FEL light source

Slides WEZZPLS3 [2.869 MB]

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reference for this paper ※ https://doi.org/10.18429/JACoW-IPAC2019-WEZZPLS3

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paper received ※ 14 May 2019 paper accepted ※ 20 May 2019 issue date ※ 21 June 2019

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WEPMP016

The Design and Preliminary Test of a Stripline Kicker for HALS

kicker, impedance, vacuum, high-voltage

2338

W. Liu, F.L. Shang, L. Shang, W.B. Song, Z.B. Sun
USTC/NSRL, Hefei, Anhui, People’s Republic of China

Stripline kicker is an important components of both on-axis longitudinal accumulation and on-axis swap out injection schemes in HALS (Hefei Advanced Light Source). After more than one year of R&D, construction of the first prototype is completed. The kicker performance is simulated by CST. The results show that in the range of 0~1GHz, on differential mode, S11 is less than - 23.7dB. In order to facilitate installation, the extension part and PTFE bracket were designed. The assembly of kicker and feedthrough has been tested with pulse generator and network analyser.

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reference for this paper ※ https://doi.org/10.18429/JACoW-IPAC2019-WEPMP016

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paper received ※ 25 April 2019 paper accepted ※ 20 May 2019 issue date ※ 21 June 2019

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WEPMP017

A New Nonlinear Kicker Design and Measurement

kicker, injection, storage-ring, lattice

2342

W.B. Song, W. Liu, Y. Lu, F.L. Shang, L. Shang, Z.B. Sun
USTC/NSRL, Hefei, Anhui, People’s Republic of China

Funding: Work supported by The National Key Research and Development Program of China(2016YFA0402000) and Pre-research Project of Hefei Advanced Light Source
For the beam injection of HALS, a feasible injection scheme is proposed and a single-pulse nonlinear kicker has been designed for off-axis injection. The kicker has been improved on the basis of the previous designed one, and the structure of the kicker was simulated by OPERA, and the prototype has been processed and measured. The results showed that the kicker designed in this paper has less influence on stored beam and lower difficulty in location.

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reference for this paper ※ https://doi.org/10.18429/JACoW-IPAC2019-WEPMP017

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paper received ※ 26 April 2019 paper accepted ※ 20 May 2019 issue date ※ 21 June 2019

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WEPMP021

Frequency Modulated Capture of Cooled Coasting Ion Beams

emittance, low-level-rf, injection, operation

2356

S.C.P. Albright, M.E. Angoletta
CERN, Geneva, Switzerland

Transverse space charge effects in the Low Energy Ion Ring (LEIR) at CERN have been shown to be a major source of particle losses, which can be mitigated with a larger RMS longitudinal emittance. However, due to electron cooling during the injection plateau, the longitudinal density is very high prior to RF capture. In addition there is an uncontrolled cycle to cycle variation in the revolution frequency of the coasting beam on the flat bottom, which degrades the beam quality at capture. In this paper we show that applying an RF frequency modulation during the capture process allows both a controlled blow-up of the longitudinal emittance and a very good reproducibility in the longitudinal distribution, which in turn improves beam transmission through the machine.

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reference for this paper ※ https://doi.org/10.18429/JACoW-IPAC2019-WEPMP021

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paper received ※ 29 April 2019 paper accepted ※ 20 May 2019 issue date ※ 21 June 2019

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WEPMP022

Design and Construction of the CERN SPS Extraction Protection Elements for LIU

extraction, vacuum, quadrupole, brightness

2359

B. Balhan, C. Baud, J.C.C.M. Borburgh, M.A. Fraser, M. Hourican, L.O. Jorat, F.-X. Nuiry, S. Pianese
CERN, Geneva, Switzerland

At CERN, the SPS synchrotron is equipped with two fast extraction channels towards the LHC. As a part of the LHC injector upgrade project (LIU), the protection devices upstream of the septa in both extraction channels will be upgraded. Various failure scenarios have been studied and presented in the past, but the definitive approach for the equipment protection upgrade for each channel has now been determined. This paper describes the consequences of the most significant failure scenarios and the impact of the heat deposition in the diluter. The resulting material stresses are evaluated. The detailed layout for the extraction protection equipment for each extraction channel is outlined. The final layout consists of a extended diluter in Long Straight Section (LSS) 6 (TPSG6) and the installation of an additional movable absorber (TPSC4) upstream of the quadrupole in front of the existing protection equipment in LSS 4. The detailed mechanical design of the TPSC4 and the construction status of both TPSC4 and TPSG6 are discussed.

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reference for this paper ※ https://doi.org/10.18429/JACoW-IPAC2019-WEPMP022

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paper received ※ 10 May 2019 paper accepted ※ 20 May 2019 issue date ※ 21 June 2019

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WEPMP032

Tracking Simulations of Shadowing Electrostatic Septum Wires by Means of Bent Crystals

extraction, septum, optics, experiment

2395

F.M. Velotti, M.A. Fraser, B. Goddard, V. Kain, L.S. Stoel
CERN, Meyrin, Switzerland

The Super Proton Synchrotron (SPS) slow extraction is a third integer resonant extraction and hence suffers from high losses at the electrostatic septum (ZS). This is one of the main limiting factors for the maximum number of Protons On Target (POT) deliverable from the SPS to the North Area (NA). A concept to significantly reduce the extraction losses via shadowing of the electrostatic septum wires using an upstream bent crystal has been proposed in *, predicting a loss reduction of up to 50% for the prototype system installed in 2018. Following the successful experimental demonstration of the concept with beam **, detailed tracking simulations have been performed to fully understand the results obtained. Further insights, such as the effective ZS width and its alignment, could be deduced by exploiting the response of the extraction loss as a function of the two degrees of freedom of the crystal (position and angle). In this paper, the beam dynamics simulations are discussed together with the implementation of the bent crystal into the simulation framework. A comparison with measurements is presented before proposals for new configurations and parameters are discussed.
* F.M. Velotti, et al., "Reduction of Resonant Slow Extraction Losses…", IPAC’18.
** F.M. Velotti, M.A. Fraser, et al., "Experimental SPS Slow Extraction Loss Reduction…", this conf.

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paper received ※ 15 May 2019 paper accepted ※ 20 May 2019 issue date ※ 21 June 2019

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WEPMP035

Model and Measurements of CERN-SPS Slow Extraction Spill Re-Shaping - the Burst Mode Slow Extraction

extraction, experiment, operation, sextupole

2406

M. Pari, M.A. Fraser, B. Goddard, V. Kain, L.S. Stoel, F.M. Velotti
CERN, Geneva, Switzerland

The ENUBET ("Enhanced NeUtrino BEams from kaon Tagging") Project aims at reaching a new level of precision of the short-baseline neutrino cross section measurement by using an instrumented decay tunnel. The North Area (NA) experimental facility of the Super Proton Synchrotron (SPS) offers the required infrastructure for the experiment. A new slow extraction type, consisting of bursts of many consecutive millisecond spills within one macro spill, has been modeled and tested for the ENUBET Project. The burst-mode slow extraction has been tested for the first time at CERN-SPS, and MADX simulations of the process have been developed. In this paper the experimental results obtained during the test campaign are presented along with the results of the quality of the produced spill and comparing it with predictions from simulations.

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reference for this paper ※ https://doi.org/10.18429/JACoW-IPAC2019-WEPMP035

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paper received ※ 12 May 2019 paper accepted ※ 20 May 2019 issue date ※ 21 June 2019

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WEPMP038

Combined MCNP/Turtle Simulation of the SINQ Beam Line at PSI-HIPA

target, proton, scattering, optics

2410

D. Reggiani, D.C. Kiselev, M. Seidel, V. Talanov, M. Wohlmuther
PSI, Villigen PSI, Switzerland

With a nominal beam power of nearly 1.4 MW, the PSI High Intensity Proton Accelerator (HIPA) complex is currently at the forefront of the high intensity frontier of particle accelerators. A key issue of such facilities is the minimization of beam losses that could lead to excessive activation of beam line components. At HIPA, the SINQ beam line is particularly subject to relatively large losses since it receives the highly divergent beam scattered off a 40 or 60 mm thick muon production graphite target (TE). So far, for HIPA, beam line simulations have been carried out only by means of the matrix multiplication codes TRANSPORT and TURTLE. Although very efficient, such tools do not allow a precise determination of beam losses whenever targets and collimators are substantially affecting the beam optics. A true understanding of how beam halo and the low momentum tail contribute to the measured losses can only be achieved by complementing the traditional simulations techniques by a tool that can transport beam particles in different materials and, at the same time, handle complex geometries like the ones of collimators situated in the beam line. Moreover, such an improved beam line simulation would give a significant contribution in evaluating the feasibility of the SINQ beam rotation system currently under study. In this paper we present a simulation of the SINQ beam line combining MCNP models of TE and collimator sections with the TURTLE computation of the magnetic channel.

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reference for this paper ※ https://doi.org/10.18429/JACoW-IPAC2019-WEPMP038

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paper received ※ 15 May 2019 paper accepted ※ 22 May 2019 issue date ※ 21 June 2019

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WEPMP040

Machine Protection Aspects of High-Voltage Flashovers of the LHC Beam Dump Dilution Kickers

kicker, operation, vacuum, high-voltage

2418

C. Wiesner, W. Bartmann, C. Bracco, M. Calviani, E. Carlier, L. Ducimetière, M.I. Frankl, M.A. Fraser, S.S. Gilardoni, B. Goddard, V. Gomes Namora, T. Kramer, A. Lechner, N. Magnin, M. Meddahi, A. Perillo-Marcone, T. Polzin, L.C. Richtmann, V. Rizzoglio, V. Senaj, J.A.F. Somoza, D. Wollmann
CERN, Geneva, Switzerland

The LHC Beam Dump System is required to safely dispose of the energy of the stored beam. In order to reduce the energy density deposited in the beam dump, a dedicated dilution system is installed. On July 14, 2018, during a regular beam dump at 6.5 TeV beam energy, a high-voltage flashover of two vertical dilution kickers was observed, leading to a voltage breakdown and reduced dilution in the vertical plane. It was the first incident of this type since the start of LHC beam operation. In this paper, the flashover event is described and the implications analysed. Circuit simulations of the current in the magnet coil as well as simulations of the resulting beam sweep pattern are presented and compared with the measurements. The criticality of the event is assessed and implications for future failure scenarios are discussed.

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reference for this paper ※ https://doi.org/10.18429/JACoW-IPAC2019-WEPMP040

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paper received ※ 14 May 2019 paper accepted ※ 20 May 2019 issue date ※ 21 June 2019

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WEPMP042

Reduction of Stored Beam Oscillations During Injection at Diamond Light Source

kicker, injection, storage-ring, timing

2426

R.T. Fielder, M. Apollonio, R. Bartolini, C. Bloomer, I.P.S. Martin
DLS, Oxfordshire, United Kingdom

At Diamond injection is performed by means a of a four kicker off-axis system, relying on a perfect timing and amplitude setting to produce a closed bump. Ageing of some of the kicker vessel components has progressively spoiled the performance of the system, causing oscillations in the stored beam. Various schemes to control these oscillations have been considered including introducing an additional compensating kicker, and installing a non-linear injection kicker. Results of simulations analysing these schemes are presented, along with measurements taken in the storage ring using an existing pinger magnet. The effects of the reduction on the quality of beam seen by beamlines is also considered.

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reference for this paper ※ https://doi.org/10.18429/JACoW-IPAC2019-WEPMP042

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paper received ※ 14 May 2019 paper accepted ※ 23 May 2019 issue date ※ 21 June 2019

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WEPMP045

Higher Multipoles in 3rd Integer Resonance Extraction

extraction, octupole, sextupole, multipole

2437

V.P. Nagaslaev
Fermilab, Batavia, Illinois, USA
K.A. Brown
BNL, Upton, Long Island, New York, USA
M. Tomizawa
KEK, Ibaraki, Japan

The efficiency of slow extraction is becoming a limiting factor, as the demand for delivered beam power is constantly growing. New methods for improving extraction efficiency include folding the extraction separatrix using the higher multipoles. In this report we discuss a simple and effective approach to determine an optimal placement of those multipoles in the storage ring. This allows reduction of the beam losses and therefore, the level of prompt and residual radioactivity in the accelerator components and surrounding buildings by as much as 40% or more. We also explore here manipulating the higher order effects produced in the pure sextupole configurations for the same purpose and demonstrate that similar results can be achieved by only rearranging the sextupole magnets in the lattice.

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reference for this paper ※ https://doi.org/10.18429/JACoW-IPAC2019-WEPMP045

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paper received ※ 10 May 2019 paper accepted ※ 22 May 2019 issue date ※ 21 June 2019

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WEPMP051

Impedance Study of a New Septum Chamber of SPEAR3

impedance, septum, vacuum, storage-ring

2447

K. Tian, J. Langton, J.J. Sebek
SLAC, Menlo Park, California, USA

Funding: Work supported by US Department of Energy Contract DE-AC03-76SF00515.
A new Septum magnet and chamber has been designed for the storage ring as a part of the accelerator improvement plan for operating a lower emittance lattice in SPEAR3. Therefore it is necessary to analyze the impedance effects on the beam from the new Septum chamber. Due to the complex design at the downstream transition of the Septum chamber, the longitudinal impedance is particular of concern. In this paper, we will present numerical simulation results for this particular component as well as the general analysis for the impedance effects of the whole chamber.

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reference for this paper ※ https://doi.org/10.18429/JACoW-IPAC2019-WEPMP051

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paper received ※ 14 May 2019 paper accepted ※ 20 May 2019 issue date ※ 21 June 2019

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WEPGW009

DEVELOPMENT OF THE ELECTRON BEAM PROBE FOR HADRON SYNCHROTRONS.

electron, hadron, proton, experiment

2480

M. Droba, C. Hübinger, O. Meusel, H. Podlech, K.I. Thoma
IAP, Frankfurt am Main, Germany
O.R. Jones, M. Wendt, F. Zimmermann
CERN, Meyrin, Switzerland

Funding: BMBF 05P18RFRB2
Non-invasive diagnostics is essential to get important information about intense hadron beams, e.g. the transverse beam profile, which is indispensable in order to attain high brilliance and luminosity for upgrades on present machines and for future projects. Furthermore, it can be used to optimise parameter settings in environment of the running machine. An electron beam probe (EBP) is a beam diagnostics instrument which scans a low energy, low current electron beam through a hadron beam and obtains information from the detected response. The electrons are shot perpendicular through the hadron beam to be examined, which causes deflection in the beam potential of the intense hadron bunch, that needs to be detected and further analysed. We propose to build the EBP scanning apparatus for synchrotrons under ultra-high vacuum condition. The results of multi particle simulations evaluating limitations the expected measurement potential and limitations are presented. This work will be performed in collaboration with CERN.

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reference for this paper ※ https://doi.org/10.18429/JACoW-IPAC2019-WEPGW009

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paper received ※ 11 May 2019 paper accepted ※ 20 May 2019 issue date ※ 21 June 2019

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WEPGW011

Development of a Silicon Strip Detector for Novel Accelerators at Sinbad

electron, detector, acceleration, linac

2487

S. Jaster-Merz, R.W. Aßmann, F. Burkart, U. Dorda, U. Kraemer, E. Panofski, M. Stanitzki
DESY, Hamburg, Germany

At the SINBAD facility (DESY Hamburg), novel particle acceleration techniques like dielectric laser acceleration (DLA) structures will be tested using the ARES linac. Due to the small size of these structures, the accelerated electron beams only have a very low (sub-pC) charge. To determine the energy distribution of these beams, a silicon strip detector for the ARES linac spectrometer is currently under development. This detector fulfils the requirements of high spatial resolution for low charge density beams. The detector consists of two 1 cm x 1 cm silicon strip sensors and readout components. The design of the detector, its components and an estimate of its behaviour for a specific electron beam distribution are presented and discussed.

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reference for this paper ※ https://doi.org/10.18429/JACoW-IPAC2019-WEPGW011

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paper received ※ 17 April 2019 paper accepted ※ 22 May 2019 issue date ※ 21 June 2019

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WEPGW017

Continuous Bunch-by-Bunch Reconstruction of Short Detector Pulses

detector, bunching, storage-ring, experiment

2501

J.L. Steinmann, M. Brosi, M. Caselle, B. Kehrer, M. Martin, A.-S. Müller, M.M. Patil, P. Schreiber
KIT, Karlsruhe, Germany

Funding: This work is funded by the BMBF contract number: 05K16VKA
The KAPTURE system (KArlsruhe Pulse Taking and Ultrafast Readout Electronics), developed at the Karlsruhe Institute of Technology (KIT), was designed to digitize detector pulses during multi-bunch operation at the KIT storage ring KARA (Karlsruhe Research Accelerator). KAPTURE provides digitization for pulses at rates of 500 MHz using up to 4 sampling points per pulse to record each bunch and each turn for potentially unlimited time. The new KAPTURE-2 system now provides eight sampling points per pulse, including baseline sampling between pulses, which allows improved reconstruction of the pulse shape. The advanced reconstruction of the pulse shape is realized with a highly parallelised implementation on GPU. The system will be used for the investigation on longitudinal beam dynamics e.g. by measuring instability induced CSR fluctuations or arrival time oscillations. This contribution will report on first results of the KAPTURE-2 system at KARA.

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reference for this paper ※ https://doi.org/10.18429/JACoW-IPAC2019-WEPGW017

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paper received ※ 15 May 2019 paper accepted ※ 20 May 2019 issue date ※ 21 June 2019

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WEPGW025

High Level Software for Beam 6D Phase Space Characterization

emittance, diagnostics, gun, quadrupole

2522

V. Martinelli, D. Alesini, M. Ferrario, A. Giribono, S. Pioli, C. Vaccarezza, A. Variola
INFN/LNF, Frascati, Italy
A. Bacci
INFN-Milano, Milano, Italy

Operation of modern particle accelerators require high qualitity beams and conseguently sensitive diagnostic system in order to monitories and characterize the beam during the acceleration and transport. A turn-key high level software BOLINA (Beam Orbit for Linear Accelerators) has been developed to fully characterise the 6D beam phase space in order to help operator during commissioning with an easily scalable suite for any high brightness LINAC. In this work will be presented the diagnostic toolkit is presented as designed for the ELI-NP Gamma Beam System (GBS) a radiation source based on the Compton back scattering effect able to provide tunable gamma rays in the 0.2-20 MeV range with narrow bandwidth (0.3% and a high spectral density (10⁴ photons/sec/eV) by the Compton backscattering effect. BOLINA suite is design to be machine independent, thanks to the file exchanges with the EPICS based control system. Simulation of raw data of the ELI-NP-GBS accelerator has been used to test the capabilities of the diagnostic toolkit.

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reference for this paper ※ https://doi.org/10.18429/JACoW-IPAC2019-WEPGW025

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paper received ※ 15 May 2019 paper accepted ※ 20 May 2019 issue date ※ 21 June 2019

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WEPGW032

Evaluation of 2-D Transverse Beam Profile Monitor Using Gas Sheet at J-PARC LINAC

injection, linac, factory, experiment

2539

J. Kamiya, Y. Hikichi, M. Kinsho, K. Moriya, N. Ogiwara, K. Okabe
JAEA/J-PARC, Tokai-mura, Japan
K. Wada
Tokyo Electronics Co. Ltd., Kokubunji, Tokyo, Japan
I. Yamada
Doshisha University, Graduate School of Engineering, Kyoto, Japan

A transverse beam profile monitor, which detects ions or luminescence generated by the interaction between the beam and the gas molecules distributed in a sheet shape, has been developed in the J-PARC LINAC. To know about the gas density distribution of the sheet-shaped gas, which affects the intensity distribution of the detected signal, the calculation by the Monte Carlo simulation code was performed. The calculation results showed that the gas with a narrow width along beam direction distributes enough uniformly within a realistic beam cross-sectional size. In addition, the unsaturated region against the MCP voltage and the injected gas pressure are evaluated based on the measurement with a beam. The results showed that the measurement in the low injected gas pressure with the appropriate applied voltage range is important to measure the beam profile in the unsaturated region.

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reference for this paper ※ https://doi.org/10.18429/JACoW-IPAC2019-WEPGW032

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paper received ※ 29 April 2019 paper accepted ※ 23 May 2019 issue date ※ 21 June 2019

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WEPGW034

Development of L-band Cavity BPM for STF

cavity, electron, electronics, linac

2547

S.W. Jang, E.-S. Kim
KUS, Sejong, Republic of Korea
H. Hayano
KEK, Ibaraki, Japan

We developed a L-band beam position monitor with position resolution of few hundred nano meter for Superconducting Test Faciliy(STF) in KEK. The L-band BPM was developed to install inside the superconducting cryomodule of STF in KEK and it’s test was performed at Accelerator Test Facility in KEK. The three L-band BPM are fabricated and installed at the end of Linac of ATF. The position resolution measurement was performed with new L-band BPM electronics. In this talk, we will describe about the development of L-band BPM and its beam test results of nano meter level beam position resolution with new electronics system.

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reference for this paper ※ https://doi.org/10.18429/JACoW-IPAC2019-WEPGW034

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paper received ※ 15 May 2019 paper accepted ※ 19 May 2019 issue date ※ 21 June 2019

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WEPGW037

Development of a Dense Gas Sheet Target for a 2D Beam Profile Monitor

electron, experiment, vacuum, target

2554

N. Ogiwara, Y. Hori
J-PARC, KEK & JAEA, Ibaraki-ken, Japan
Y. Hikichi, J. Kamiya, M. Kinsho
JAEA/J-PARC, Tokai-Mura, Naka-Gun, Ibaraki-Ken, Japan
I. Yamada
Doshisha University, Graduate School of Engineering, Kyoto, Japan

We have been developing a dense gas sheet target to realize a non-destructive and fast-response beam profile monitor for the accelerators in J-PARC. The beaming effect in vacuum science and technology has been employed for making a gas sheet. The gas sheet with a thickness of ~ 1 mm and the density of 2 x 10^-4 Pa was successfully obtained. Then, we have successfully measured the profiles of the 400 MeV H⁻ ion beam in J-PARC linac by detecting the ions generated through the collision of this gas sheet to the H⁻ beam. This time, we have developed the gas sheet with the density of more than 10-3 Pa using a circular slit. The details of the new gas sheet generator will be shown.

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reference for this paper ※ https://doi.org/10.18429/JACoW-IPAC2019-WEPGW037

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paper received ※ 20 May 2019 paper accepted ※ 23 May 2019 issue date ※ 21 June 2019

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WEPGW041

Development of a Gas Distribution Measuring System for Gas Sheet Beam Profile Monitor

electron, injection, experiment, detector

2567

I. Yamada
Doshisha University, Graduate School of Engineering, Kyoto, Japan
Y. Hikichi, J. Kamiya, M. Kinsho
JAEA/J-PARC, Tokai-mura, Japan
N. Ogiwara
J-PARC, KEK & JAEA, Ibaraki-ken, Japan

The beam profile monitor is needed for measuring one of the beam parameters of high intensity accelerator to avoid radioactivating the systems. A monitor with sheet-shaped gas that can measure the beam profile nondestructively in two dimensions is developing. One of issues to introduce the monitor in accelerator is that the gas distribution is not uniform. Obtaining correct beam profile data needs to measure the gas distribution data because signal from the monitor is in proportion to beam intensity and gas distribution. A system analyzing distribution of ions produced from the gas using electron beam to measuring gas distribution in three dimensions is developing. An electron gun that produces ideal narrow beam, electrodes that forms parallel electric field toward micro-channel plate(MCP), and phosphor constitute the system. The electron beam that ionizes the gas which needs to be measured, produced ions are induced to MCP, and image on phosphor gives gas distribution data. In preliminary experiment for inspecting the measuring principle, experimental results agreed with simulation. The details of this system and the results of gas measuring experiment are reported.

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reference for this paper ※ https://doi.org/10.18429/JACoW-IPAC2019-WEPGW041

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paper received ※ 28 April 2019 paper accepted ※ 24 May 2019 issue date ※ 21 June 2019

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WEPGW044

Study on the Influence of Beam Transverse Position on the Cavity Bunch Length Measurement

cavity, dipole, electron, laser

2578

Q. Wang, S.M. Jiang, Q. Luo, B.G. Sun
USTC/NSRL, Hefei, Anhui, People’s Republic of China

Funding: Work supported by National Key R&D Program of China (Grant No. 2016YFA0401900 and No. 2016YFA0401903) and The National Natural Science Foundation of China (Grant No. U1832169 and No. 11575181).
Monopole modes in the resonant cavity are wildly used to obtain the beam current and the bunch length, while dipole modes are used to measure the beam transverse position. It is generally recognized that the monopole modes are independent of the beam transverse offset. In this paper, the influence of beam transverse offset on the bunch length measurement using monopole modes is analyzed. The simulation results show that the relative error of the bunch length measurement is less than 1 % when the beam offset is within 1 mm.

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reference for this paper ※ https://doi.org/10.18429/JACoW-IPAC2019-WEPGW044

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paper received ※ 25 April 2019 paper accepted ※ 20 May 2019 issue date ※ 21 June 2019

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WEPGW049

Deep Learning Applied for Multi-Slit Imaging Based Beam Size Monitor

network, SRF, synchrotron, synchrotron-radiation

2587

B. Gao, Y.B. Leng
SSRF, Shanghai, People’s Republic of China
X.Y. Xu
SINAP, Shanghai, People’s Republic of China

In order to satisfy the requirement of high speed measurement and improve the accuracy of BSM (beam size monitor), multi-slit imaging based BSM has been proposed by SSRF at 2017. However, it is very difficult to deconvolve the image and figure out the beam size, which requires dedicated algorithms to solve this issue. Deep learning is one of the most popular algorithms, which can learn to mimic any distribution of data. In the region of Beam instrumentation, they can be taught to deal with many difficult problem. In this paper, multi-layer neural network is used to process the images from the multi-slit imaging system. Training processes, struct of the neural networks and the result of the experiments will be presented.

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reference for this paper ※ https://doi.org/10.18429/JACoW-IPAC2019-WEPGW049

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paper received ※ 15 May 2019 paper accepted ※ 21 May 2019 issue date ※ 21 June 2019

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WEPGW057

Design of Stripline BPM for the SHINE Project

FEL, experiment, diagnostics, beam-diagnostic

2605

T. Wu, B. Gao, L.W. Lai, Y.B. Leng
SSRF, Shanghai, People’s Republic of China
S.S. Cao, J. Chen, Y.M. Zhou
SINAP, Shanghai, People’s Republic of China

As a under-constrution forth-generation light source in China, SHINE(Shanghai HIgh repetition rate XFEL aNd Extreme light facility) is expected to play an important role in basic scientific research in the field of materials and medicine. However, the performance of FEL depends critically on the completeness and quality of their beam diagnostic systems. Since the SHINE project will operate with bunch charge at 100pC, which is only one-quarter of that in the SXFEL, the measurement accuracy requirements for SBPM will increase significantly. On the other hand, the bunch repetition frequency of SHINE reached 1MHz, which shortened the threshold for measuring dead time. Fitting the requirement, the passband and the sampling rate design of stripline BPM is upgraded for the SHINE project. The final design was simulated using the data on the SXFEL, and the some inspiring results have been made.

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reference for this paper ※ https://doi.org/10.18429/JACoW-IPAC2019-WEPGW057

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paper received ※ 15 May 2019 paper accepted ※ 21 May 2019 issue date ※ 21 June 2019

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WEPGW058

Orbit Correction With Machine Learning

lattice, storage-ring, closed-orbit, coupling

2608

D.J. Xiao, C.P. Chu, Y.S. Qiao
IHEP, Beijing, People’s Republic of China

Orbit correction is usually an important task in the operation of accelerators. In practice, due to various errors, many devices can not operate in ideal state. By correcting the errors of magnets with corrector magnets, the beam can return to the correct position to ensure the stable operation of the accelerator. In the process of orbit correction, inaccurate BPM output will lead to incorrect correction magnet strength setting, so that the orbit correction will be impacted. BPM may make mistakes in the process of signal acquisition and current conversion. A BPM anomaly detection and predict method based on machine learning and its using in orbit correction optimization is reported in this paper. This method does not need to observe the details of BPM system, electronics technology and so on. It can monitor and predict the BPM status directly by machine learning with the information of the beam inferred from BPM and others, and optimize the orbit correction.

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reference for this paper ※ https://doi.org/10.18429/JACoW-IPAC2019-WEPGW058

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paper received ※ 15 May 2019 paper accepted ※ 22 May 2019 issue date ※ 21 June 2019

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WEPGW075

Coupling Impedance Studies of the Current Transformers at ALBA

impedance, resonance, cavity, factory

2647

T.F.G. Günzel, U. Iriso, A.A. Nosych
ALBA-CELLS Synchrotron, Cerdanyola del Vallès, Spain

ALBA is equipped with two different current transformers (FCT and DCCT), and a third one (ICT) is now in design stage to be installed in 2019. A comparative study of the different currents transformers was carried out in order to characterize their contribution to longitudinal and transverse impedance. The gap in the vacuum chamber of the current transformers was varied in order to study its effect on the heat deposited by the beam in the corresponding device and on the resonance in the longitudinal impedance spectrum. The simulation results are compared to the experience with the existing current transformers in operation.

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reference for this paper ※ https://doi.org/10.18429/JACoW-IPAC2019-WEPGW075

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paper received ※ 14 May 2019 paper accepted ※ 21 May 2019 issue date ※ 21 June 2019

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WEPGW081

Unsupervised Machine Learning for Detection of Faulty Beam Position Monitors

optics, ISOL, MMI, ECR

2668

E. Fol, J.M. Coello de Portugal, R. Tomás
CERN, Meyrin, Switzerland

Unsupervised learning includes anomaly detection techniques that are suitable for the detection of unusual events such as instrumentation faults in particle accelerators. In this work we present the application of decision trees-based algorithm to faulty BPMs detection at the LHC. This method achieves significant improvements in quality of optics measurements and allows to identify relevant signal properties that contribute to fault detection.

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reference for this paper ※ https://doi.org/10.18429/JACoW-IPAC2019-WEPGW081

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paper received ※ 14 May 2019 paper accepted ※ 21 May 2019 issue date ※ 21 June 2019

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WEPGW083

Quadrated Dielectric-Filled Reentrant Cavity Resonator as a Proton Beam Position Diagnostic

cavity, dipole, pick-up, proton

2676

S. Srinivasan, P.-A. Duperrex, J.M. Schippers
PSI, Villigen PSI, Switzerland

Funding: This project has received funding from the European Union’s Horizon 2020 research and innovation programme under the Marie Sk³odowska-Curie grant agreement No 675265
Low proton beam intensities (0.1-40 nA) are used for medical treatment of tumours at the PROSCAN facility in Paul Scherrer Institut (PSI). A cavity resonator using four quadrants operating in a dipole mode resonance has been developed to measure beam positions at these low intensities. The TM110 resonance frequency of 145.7 MHz is matched to the second harmonic of the beam pulse repetition rate (i.e.72.85 MHz). HFSS (High Frequency Structural Simulator) provides the BPM geometry and important parameters such as pickup position; dielectric dimensions etc. Comparison of test bench measurement and simulation provides good agreement. The measured position and signal sensitivity are limited by the noise, so that a position signal can be derived at beam intensities of at least 10 nA . We will discuss potential methods to increase the sensitivity. The dipole cavity resonator can be a promising candidate as a non-invasive position di-agnostic at the low proton beam intensities used in pro-ton therapy

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reference for this paper ※ https://doi.org/10.18429/JACoW-IPAC2019-WEPGW083

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paper received ※ 14 May 2019 paper accepted ※ 21 May 2019 issue date ※ 21 June 2019

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WEPGW088

Characterisation of Electro-Optic Pickups for High Bandwidth Diagnostics at the High Luminosity LHC

pick-up, proton, luminosity, ECR

2690

A. Arteche, A. Bosco, S.M. Gibson
Royal Holloway, University of London, Surrey, United Kingdom
S.E. Bashforth, A. Bosco, S.M. Gibson, I.S. Penman
JAI, Egham, Surrey, United Kingdom
M. Krupa, T. Lefèvre
CERN, Geneva, Switzerland

Funding: Work supported by UK STFC grants ST/N001583/1, JAI at Royal Holloway University of London and CERN.
A high bandwidth electro-optical beam position monitor is under development for the High Luminosity LHC. A series of measurements of the electro-optic signals were previously obtained by an EO-BPM prototype installed in the SPS. This paper focuses on an advanced design that would further improve the sensitivity of the pick-up by optimising the shape of the metallic electrode mounted onto the crystal. The proposed upgraded electro-optic pickups significantly increase the image field profile of the passing bunch inside a lithium niobate crystal embedded within the pickup. This work is based on parametric studies, performed using CST particle studio, investigating various electro-optic (electrode and crystal) configurations. We present the expected performance of the different designs, alongside with their evaluation on a test bench, highlighting the most relevant choice for a prototype pick-up to be installed on LHC

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reference for this paper ※ https://doi.org/10.18429/JACoW-IPAC2019-WEPGW088

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paper received ※ 22 May 2019 paper accepted ※ 24 May 2019 issue date ※ 21 June 2019

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WEPGW095

Coherent Transition Radiation Spatial Imaging as a Bunch Length Monitor

radiation, electron, detector, focusing

2713

J. Wolfenden, R.B. Fiorito, C.P. Welsch
The University of Liverpool, Liverpool, United Kingdom
M. Brandin, E. Mansten, S. Thorin
MAX IV Laboratory, Lund University, Lund, Sweden
R.B. Fiorito, C.P. Welsch, J. Wolfenden
Cockcroft Institute, Warrington, Cheshire, United Kingdom
B.S. Kyle, T.H. Pacey, T.H. Pacey
UMAN, Manchester, United Kingdom
B.S. Kyle
University of Manchester, Manchester, United Kingdom
E. Mansten
Lund University, Division of Atomic Physics, Lund, Sweden
T.H. Pacey
STFC/DL/ASTeC, Daresbury, Warrington, Cheshire, United Kingdom
A.G. Shkvarunets
UMD, College Park, Maryland, USA

Funding: This work was supported by the EU under Grant Agreement No. 624890 and the STFC Cockcroft Institute core Grant No. ST/G008248/1.
High-resolution bunch length measurement is a key component in the optimisation of beam quality in FELs, storage rings, and plasma-based accelerators. Simulations have shown that the profile of a coherent transition radiation (CTR) image produced by a charged particle beam is sensitive to bunch length and can thus be used as a diagnostic. This contribution presents the development progress of a novel bunch length monitor based on imaging the spatial distribution of CTR. Due to the bunch lengths studied, 10fs-100fs FWHM, the radiation of interest was in the THz range. This led to the development of a THz imaging system, which can be applied to both high and low energy electron beams. The associated benefits of this imaging distribution methodology over the typical angular distribution measurement are discussed. Building upon preliminary multi-shot proof of concept results last year, a new series of experiments have been conducted in the short pulse facility (SPF) at MAX IV. Single-shot measurements have been used to measure the exact point of maximum compression. Analysis from the proof of concept results last year, and initial results from the new measurements this year are discussed.

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reference for this paper ※ https://doi.org/10.18429/JACoW-IPAC2019-WEPGW095

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paper received ※ 14 May 2019 paper accepted ※ 21 May 2019 issue date ※ 21 June 2019

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WEPGW108

Transverse Uncorrelated Emittance Diagnostic for Magnetized Electron Beams

emittance, electron, diagnostics, cathode

2745

M.S. Stefani
ODU, Norfolk, Virginia, USA
F.E. Hannon
JLab, Newport News, Virginia, USA

Funding: This manuscript has been authored by Jefferson Science Associates, LLC under Contract No. DE-AC05-06OR23177 with the U.S. Department of Energy.
The study of magnetized electron beam has become a high priority for its use in ion beam cooling as part of Electron Ion Colliders and the potential of easily forming flat beams for various applications. In this paper, a new diagnostic is described with the purpose of studying transverse magnetized beam properties. The device is a modification to the classic pepper-pot, used in this novel context to measure the uncorrelated components of transverse emittance in addition to the typical effective emittance. The limitations of traditional methods are discussed, and simulated demonstrations of the new technique shown.

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reference for this paper ※ https://doi.org/10.18429/JACoW-IPAC2019-WEPGW108

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paper received ※ 15 May 2019 paper accepted ※ 21 May 2019 issue date ※ 21 June 2019

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WEPGW109

Double Quarter Wave Deflector Cavity Design & Simulation

cavity, coupling, operation, diagnostics

2749

M.S. Stefani
ODU, Norfolk, Virginia, USA
G.-T. Park
JLab, Newport News, Virginia, USA

Funding: This manuscript has been authored by Jefferson Science Associates, LLC under Contract No. DE-AC05-06OR23177 with the U.S. Department of Energy.
A Double Quarter Wave (DQW) Cavity has been designed, tested and installed for use in longitudinal measurements as part of a diagnostic beamline. This report will describe the design and testing used to characterize this cavity before its use in the study of a magnetized electron beam.

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reference for this paper ※ https://doi.org/10.18429/JACoW-IPAC2019-WEPGW109

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paper received ※ 15 May 2019 paper accepted ※ 23 May 2019 issue date ※ 21 June 2019

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WEPGW113

Propose a Non-Destructive Stern-Gerlach Apparatus for Measuring the Spin Polarization of Electron Beam

electron, quadrupole, polarization, software

2763

W. Liu, E. Wang
BNL, Upton, Long Island, New York, USA

Funding: Work supported by Brookhaven Science Associates, LLC under Contract No. DE-AC02-98CH10886 with the U.S. Department of Energy.
Mott polarimeter is used for measuring the spin polarization of <10 MeV electron beam destructively. We propose a nondestructive spin polarization measurement device for electron beam based on Stern-Gerlach effect, which include a magnetic quadrupole, Lorenz force compensated electric quadrupole and Beam position monitor. The magnetic quadrupole provides a spin-magnetic interaction force (or Stern-Gerlach force) for the spin polarized electrons. The electric quadrupole provides an electric field force for electrons to offset the Lorentz force induced by the magnetic quadrupole. So that the polarized electron beam only experience the gradient force in the device, which has ability to split the spin polarized electron beam. By measuring the split spin polarized electrons using high resolution beam position monitor, the polarization of electron beam can be calculated. We will present the theoretical analysis and calculation of electron motion in this device.

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reference for this paper ※ https://doi.org/10.18429/JACoW-IPAC2019-WEPGW113

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paper received ※ 01 May 2019 paper accepted ※ 20 May 2019 issue date ※ 21 June 2019

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WEPRB017

Operational Experiences with X-Ray Tomography for SRF Cavity Shape and Surface Control

cavity, controls, gun, detector

2838

H.-W. Glock, J. Knobloch, A. Neumann, Y. Tamashevich
HZB, Berlin, Germany
M. Böhnel, N. Reims
Fraunhofer IIS EZRT, Fürth, Germany
J. Kinzinger
X-RAY LAB, Sachsenheim, Germany

X-ray tomography has established as a non-destructive three-dimensional analysis tool, commercially offered by industrial vendors. Typical applications cover shape control and failure detection (voids, cracks) deep inside of complicated bulk pieces like engine blocks, bearings, turbine blades etc. We evaluated the applicability of the process for superconducting radio frequency cavities, in particular the 1.4-cell 1.3 GHz BERLinPro electron gun cavity and the 1.5 GHz single-cell VSR cavity prototype. The former experienced severe shape modifications during its tuning process and features a complicated internal stiffening construction. Thus it is a demanding challenge to measure its actual internal cavity surface shape after the complete preparation process with a resolution, sufficiently high (better than 0.2 mm) to serve as input for meaningful comparative field simulations. First tests with a vendor’s on-site X-ray source, operating at X-ray energies up to 590 keV revealed an insufficient resolution of the inner surface, attributed to the unfavorable X-ray damping characteristics of niobium. This was overcome with the aid of an accelerator-based source (X-ray spectrum up to 9 MeV), operated by Fraunhofer IIS, Fürth, Germany. Results both show significant, while understood, shape changes and indicate partial inner surface modifications of the gun cavity. Further the data evaluation process, which was needed to provide input for field simulations, raised issues because of the data set size and complexity, which are discussed in the paper.

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reference for this paper ※ https://doi.org/10.18429/JACoW-IPAC2019-WEPRB017

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paper received ※ 17 May 2019 paper accepted ※ 23 May 2019 issue date ※ 21 June 2019

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WEPRB024

Low Power RF Test of a Quadrupole-free X-Band Mode Launcher for High Brightness Applications

GUI, brightness, quadrupole, electron

2856

G. Torrisi, L. Celona, S. Gammino, O. Leonardi, G. Sorbello
INFN/LNS, Catania, Italy
G. Castorina
Sapienza University of Rome, Rome, Italy
V.A. Dolgashev
SLAC, Menlo Park, California, USA
L. Faillace
INFN-Milano, Milano, Italy
G.S. Mauro
INFN/LNL, Legnaro (PD), Italy
G. Sorbello
University of Catania, Catania, Italy
B. Spataro
INFN/LNF, Frascati, Italy

In this work we present the low power RF characterization of a novel TM01 X-band mode launcher for the new generation of high brightness RF photo-injectors. The proposed mode launcher exploits a fourfold symmetry which minimizes both the dipole and the quadrupole fields in order to mitigate the emittance growth in the early stages of the acceleration process. Two identical aluminum mode launchers have been assembled and measured in back-to-back configurations for three different central waveguide lengths. From the back-to-back results we infer the performance of each mode launcher. The low power RF test, performed at the Istituto Nazionale di Fisica Nucleare Laboratori Nazionali del Sud (INFN-LNS), validate both the numerical simulations and the quality of fabrication. An oxygen-free high-conductivity copper version of the device is being manufactured for high power and ultra high vacuum tests that are planned to be conducted at SLAC

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reference for this paper ※ https://doi.org/10.18429/JACoW-IPAC2019-WEPRB024

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paper received ※ 09 April 2019 paper accepted ※ 20 May 2019 issue date ※ 21 June 2019

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WEPRB026

Simulations of Beam Loading Compensation in a Wideband Accelerating Cavity Using a Circuit Simulator Including a LLRF Feedback Control

controls, cavity, feedback, vacuum

2863

F. Tamura, M. Nomura, T. Shimada, M. Yamamoto
JAEA/J-PARC, Tokai-Mura, Naka-Gun, Ibaraki-Ken, Japan
M. Furusawa, K. Hara, K. Hasegawa, C. Ohmori, Y. Sugiyama, M. Yoshii
KEK, Tokai, Ibaraki, Japan

Magnetic alloy cavities are employed in the J-PARC RCS to generate high accelerating voltages. The cavity, which is driven by a vacuum tube amplifier, has a wideband frequency response and the beam loading in the cavity is multiharmonic. Therefore, the tube must generate a multiharmonic output current. An LTspice circuit model is developed to analyze the vacuum tube operation and the compensation of the multiharmonic beam loading. The model includes the cavity, tube amplifier, beam current, and LLRF feedback control. The feedback control consists of the I/Q demodulator including low pass filters, PI control, and I/Q modulator. In this presentation, we present the implementation of the LLRF functions in the LTspice simulations. The preliminary simulation results are also presented. The simulations fairly agree with the beam test results.

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reference for this paper ※ https://doi.org/10.18429/JACoW-IPAC2019-WEPRB026

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paper received ※ 23 April 2019 paper accepted ※ 20 May 2019 issue date ※ 21 June 2019

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WEPRB027

Electromagnetic Design and Characterization of an S-band 3-Cell RF Accelerating Cavity

cavity, emittance, electron, acceleration

2867

G.R. Montoya Soto
Universidad de Guanajuato, División de Ciencias e Ingenierías, León, Mexico
C. Duarte Galván, C.A. Valerio
ECFM-UAS, Culiacan, Sinaloa, Mexico
B. Yee-Rendón
JAEA/J-PARC, Tokai-mura, Japan

An S-Band (2998 MHz) RF cavity to accelerate electrons was developed taking into account the beam space charge, the relativistic change in velocity of the low energy beam particle distribution through the cavity and the emittance growth. The electromagnetic design and geometry optimization were done using the codes Poisson Superfish and CST Studio. In addition, beam dynamics simulations were done using the program Travel to optimize the emittance and take into account the space charge effect. The machining was done in a CNC machining center. Measurements of the cavity resonance frequencies were carried out and compared with the obtained by the simulations with good agreement between them.

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reference for this paper ※ https://doi.org/10.18429/JACoW-IPAC2019-WEPRB027

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paper received ※ 30 April 2019 paper accepted ※ 20 May 2019 issue date ※ 21 June 2019

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WEPRB029

Design of the Elliptical Superconducting Cavities for the JAEA ADS

cavity, superconducting-cavity, SRF, acceleration

2873

B. Yee-Rendón, Y. Kondo, F.M. Maekawa, S.I. Meigo, J. Tamura
JAEA/J-PARC, Tokai-mura, Japan

The superconducting CW proton linear accelerator for an Accelerator Driven Subcritical System (ADS) proposed by Japan Atomic Energy Agency (JAEA) employs elliptical cavities for the final acceleration of 180 MeV to 1.5 GeV. Since this energy region implies a change of beta from 0.55 to 1, two cavity models were developed using the geometrical betas of 0.68 and 0.89 to improve the acceleration efficiency. The study of the electromagnetic design was simulated using SUPERFISH (SF) code and python program to do variable scan, the results were benchmarked with CST Microwave Studio program (CST).

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reference for this paper ※ https://doi.org/10.18429/JACoW-IPAC2019-WEPRB029

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paper received ※ 18 April 2019 paper accepted ※ 22 May 2019 issue date ※ 21 June 2019

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WEPRB032

Superconducting Elliptical Cavities Developed in IMP for the CiADS

cavity, HOM, multipactoring, operation

2883

Y.L. Huang, Y. He, R. Huang, T.C. Jiang, L.B. Liu, S.H. Liu, T. Tan, R.X. Wang, Z.J. Wang, S.H. Zhang, S.X. Zhang
IMP/CAS, Lanzhou, People’s Republic of China

Multicell superconducting radio frequency (SRF) ellip-tical cavities are proposed for efficient acceleration of proton beam in the Chinese initiative Accelerator Driven Subcritical System (CiADS). Two families of such cavities will be used in the driver SRF Linac, the first family corresponding to βopt=0.62 cavities that will be used to accelerate the H⁺ beam from 175 MeV to 377 MeV and the second family corresponding to βopt=0.82 cavities that will accelerate the H⁺ beam from 377 MeV to 500 MeV, with the possibility to upgrade to 1 GeV and higher. The electromagnetic optimization of the cavities with the HOM, wakefield and multipacting analysis will be dis-cussed in this paper.

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reference for this paper ※ https://doi.org/10.18429/JACoW-IPAC2019-WEPRB032

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paper received ※ 14 May 2019 paper accepted ※ 23 May 2019 issue date ※ 21 June 2019

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WEPRB034

Study on the Design of the X-band Waveguide-damped Structure

wakefield, damping, GUI, HOM

2886

X.X. Huang, W. Fang, Z.T. Zhao
SSRF, Shanghai, People’s Republic of China
A. Grudiev
CERN, Meyrin, Switzerland

The design of waveguide-damped structure is optimized to reduce the magnitudes of surface electromagnetic fields and strongly suppress long-range transverse wakefields of the 380 GeV Compact Linear Collider facility currently under study. The optimization is mainly discussed with the elliptical shape of the iris, the wall shape of the damping waveguides, the position of the high-order-mode damping loads and the widths of the waveguide openings of the entire sequence of damping waveguides.

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reference for this paper ※ https://doi.org/10.18429/JACoW-IPAC2019-WEPRB034

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paper received ※ 13 May 2019 paper accepted ※ 22 May 2019 issue date ※ 21 June 2019

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WEPRB044

Microphonics Simulation and Parameters Design of the SRF Cavities for CiADS

cavity, linac, beam-loading, proton

2903

J.Y. Ma, G. Huang
IMP/CAS, Lanzhou, People’s Republic of China

The CiADS (China initiative Accelerator Driven System) proton Linac is designed to accelerate CW beams of up to 500 MeV and 5mA, which is delivered to the spallation target. Since the beam power will eventually reach 2.5 MW, the beam loss should be restricted, which is sensitive to the SC cavity stability. On CW operating mode, the main perturbation to the cavity is microphonics. This paper will describe a set of tools developed to simulate performance of the cavity and its LLRF control system in order to ensure proper cavity operation under microphonics. The simulation tools describe a relationship between microphonics and the RF parameters. The microphonics effect to the cavity is simulated. The tolerated intensity of microphonics is determined by simulation, in order to satisfy the stability of amplitude and phase with 0.1% and 0.1 degree respectively.

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reference for this paper ※ https://doi.org/10.18429/JACoW-IPAC2019-WEPRB044

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paper received ※ 15 May 2019 paper accepted ※ 22 May 2019 issue date ※ 21 June 2019

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WEPRB045

Suppression of Secondary Electron Yield Effect in the 650MHz/800kW Klystron for CEPC

cavity, klystron, electron, multipactoring

2906

X. He, C. Meng, S. Pei, J.L. Wang, O. Xiao, N. Zhou
IHEP, Beijing, People’s Republic of China

The circular electron positron collider (CEPC) is in pre-research, it will need more than two hundred 650MHz/800kW klystrons. The secondary electron yield (SEY) effect suppression is very important for the klystron working stable. The simulation uses an incident primary electron source and considers all the phases and power levels of the input microwave. Two methods are simulated for the SEY suppression. The groove cutting on the nose of cavities is much simple while the TiN coating can suppress better. The effect after groove cutting on nose is also simulated and the corresponding compensations are adopted. For simplify the fabrication progress as well as some experience that can be referenced, the groove cutting method is adopted finally for the first klystron prototype, which is expected to be available in the summer of 2019.

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reference for this paper ※ https://doi.org/10.18429/JACoW-IPAC2019-WEPRB045

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paper received ※ 13 May 2019 paper accepted ※ 22 May 2019 issue date ※ 21 June 2019

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WEPRB046

Development of Flexible Waveguide for High Power High Vacuum Applications in S-band

GUI, vacuum, factory, linac

2909

X. He, B. Deng, J. Lei, C. Meng, S. Pei
IHEP, Beijing, People’s Republic of China

A novel flexible waveguide is developed for S band 2856 MHz, which is a standard WR284 waveguide. The surface of the flexible waveguide is plated with Oxygen-free High Conductivity (OFHC) copper for the purpose of welding with the stainless steel flange in the vacuum furnace, for the flexible waveguide itself is made of brass. The prototype has got a certain amount of deformation which will be much more convenient for the connection between two hard waveguides. It also has a good measurement results of the lower power microwave test, and the 72 hours vacuum leakage test shows a satisfactory vacuum performance, no obvious surface collapse is observed. The high power test will be conducted after our high power test facility is available, which will tell us the maximal power level of the flexible waveguide prototype.

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reference for this paper ※ https://doi.org/10.18429/JACoW-IPAC2019-WEPRB046

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paper received ※ 13 May 2019 paper accepted ※ 23 May 2019 issue date ※ 21 June 2019

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WEPRB048

Design, Fabricate, and Tuning of X-Band Deflecting Structure for CERN

cavity, GUI, free-electron-laser, electron

2915

J.H. Tan, W. Fang, Q. Gu, X.X. Huang, Z.T. Zhao
SSRF, Shanghai, People’s Republic of China

A 20-cell x-band deflecting structure for CERN has been finished, and now is under high power conditioning at XBOX of CERN.

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reference for this paper ※ https://doi.org/10.18429/JACoW-IPAC2019-WEPRB048

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paper received ※ 14 May 2019 paper accepted ※ 21 May 2019 issue date ※ 21 June 2019

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WEPRB049

HOM Analysis of the 4-cell Superconducting Cavity on CTFEL Facility

HOM, cavity, FEL, electron

2918

X. Luo, T.H. He, C.L. Lao, L.J. Shan, X.M. Shen, D. Wu, K. Zhou
CAEP/IAE, Mianyang, Sichuan, People’s Republic of China
F. Wang
PKU, Beijing, People’s Republic of China

The higher order modes (HOMs) of the 1.3GHz 4-cell cavity on CTFEL facility is analyzed in this paper. The passbands of the HOMs in the 4-cell cavity were simulat-ed, and the most harmful modes were determined. The power of the wakefields was estimated. By microwave test at room temperature, the frequencies of the HOMs were measured, as well as the external Q’s of the HOM cou-plers. Besides, a frequency distribution measurement system was built. The HOM signal excited by beam at 2 K temperature is measured, and some preliminary results are obtained. The measurement techniques and results of the HOM damping performance are presented in this paper.

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reference for this paper ※ https://doi.org/10.18429/JACoW-IPAC2019-WEPRB049

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paper received ※ 14 May 2019 paper accepted ※ 22 May 2019 issue date ※ 21 June 2019

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WEPRB050

Multipacting Studies of the Coaxial Coupler for BNCT DTL

multipactoring, DTL, impedance, neutron

2921

M.X. Fan, A.H. Li, B. Li, J. Peng, P.H. Qu, A.X. Wang, Y. Wang, X.L. Xiaolei
IHEP CSNS, Guangdong Province, People’s Republic of China
Q. Chen, S. Fu, H.C. Liu
IHEP, Beijing, People’s Republic of China
X.L. Wu
DNSC, Dongguan, People’s Republic of China

Funding: Youth Innovation Promotion Association of CAS (2015011) Program for GuangDong Introducting Innovative and Enterpreneurial Teams (2017ZT07S225)
Multipacting is a phenomenon in which electrons grow sharply under certain conditions in a RF structure. It may lead to the breakdown or even damage to the equipment. Therefore, it is very important to calculate the Multipact-ing range in the RF equipment design. Since the phe-nomenon is too complicated to use the formula to fully predict it, numerical simulation is employed. There are many computer codes (such as Track3P, MultiPac, CST PS, etc.) used to simulate the phenomenon, but most of them are not commercial. In this paper, theories used in coaxial line for predicting multipacting are introduced; the CST PS is chosen to simulate the multipacting of coaxial coupler for BNCT DTL; finally, methods of sup-pressing multipacting are discussed.

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reference for this paper ※ https://doi.org/10.18429/JACoW-IPAC2019-WEPRB050

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paper received ※ 11 April 2019 paper accepted ※ 23 May 2019 issue date ※ 21 June 2019

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WEPRB051

MA RF Cavity Design and Simulation for CSNS/RCS Upgrade Project

cavity, experiment, synchrotron, detector

2925

B. Wu
IHEP CSNS, Guangdong Province, People’s Republic of China
X. Li, H. Sun
IHEP, Beijing, People’s Republic of China

The dual harmonic RF system will be adapted for Chi-na Spallation Neutron Source (CSNS) upgrade project. Limited locations in CSNS/RCS are reserved to install additional three 2nd harmonic cavities. The cavity loaded by magnetic alloy (MA) material would be used. Because of the low Q factor of the MA core, the cavity cooling be-comes a very important issue in cavity design. Air-forced, indirect and direct cooling scheme were studied. The fluid thermodynamic of different cooling structure were simu-lated by ANSYS CFX which considered the anisotropy of thermal conductivity of MA core. The limitation of these cooling schemes were discussed in detail based on the simulation results. Indirect cooling experiment was done to assess the cooling efficiency and verify the simulation result. A high power test cavity cooled by water has been designed to estimate the property of the MA core and cooling effectiveness for CSNS/RCS.

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reference for this paper ※ https://doi.org/10.18429/JACoW-IPAC2019-WEPRB051

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paper received ※ 08 May 2019 paper accepted ※ 23 May 2019 issue date ※ 21 June 2019

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WEPRB052

Design of Two Types of X-Band High Power Directional Coupler

GUI, coupling, scattering, operation

2928

G. Wang, X. Lin, Y.G. Tang, C.-F. Wu
USTC/NSRL, Hefei, Anhui, People’s Republic of China

The directional coupler is one of the most widely used components in many microwave systems, which is used to distribute the power of the input microwave signal according to a desired ratio. Directional coupler may be a three-port component or a four-port component with certain specification such as frequencies, bandwidth and structure. To meet the requirements of stable coupling degree and high directivity, we designed two types of directional coupler working at 11.424 GHz with high power handling capacity. One consists of two parallel rectangular waveguides with four holes drilled along the central line of the narrow-wall for coupling the electromagnetic power from the main-waveguide to the sub-waveguide which is called H-plane directional coupler. Simulations show that the coupling degree of H-face directional coupler is 49.9 dB and the directivity is 54.5 dB .The peak electric field is about 29MV/m while operating at 200 MW peak power. The other consists of a circular main-waveguide transmitting TM01 mode and a rectangular sub-waveguide transmitting TE10 mode, called circular-rectangle waveguide directional coupler. These two waveguide are connected by six holes drilled on the side of the circular main-waveguide and along the central line of the wide-wall of the sub-waveguide. The coupling degree of this directional coupler is 50.14 dB and the directivity is 37.93 dB due to the simulation. The bandwidth is about 800MHz. The peak electric field is 404.5V/m while operating at 200 MW peak power. Comparing with the H-plane directional coupler, peak electric field of this directional coupler is lower. Low peak electric field can reduce the risk of RF breakdown and the Multipactor effect, which ensures the stable high power operation of the directional coupler.

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reference for this paper ※ https://doi.org/10.18429/JACoW-IPAC2019-WEPRB052

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paper received ※ 27 April 2019 paper accepted ※ 22 May 2019 issue date ※ 21 June 2019

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WEPRB055

Design of 3 MeV S-band Electron Linac Structure With 2.5 Bunching Cells

electron, bunching, linac, coupling

2934

Y. Joo, P. Buaphad, H.R. Lee
University of Science and Technology of Korea (UST), Daejeon, Republic of Korea
Y. Kim
KAERI, Daejon, Republic of Korea
J.Y. Lee, S. Lee
Korea Atomic Energy Research Institute (KAERI), Daejeon, Republic of Korea

Funding: UST (University of Science and Technology), KAERI (Korea Atomic Energy Research Institute)
The Korea Atomic Energy Research Institute (KAERI) has been designing several 3 MeV S-band RF electron linear accelerators (linacs) for non-destructive testing. Until now, the bunching cell of the linac has a full-cell geometry. However, to maximize the acceleration of electrons after emission from the electron gun, the geometry of the first bunching cell is modified from a full-cell to a half cell. To accelerate electron beams more gently, recently, we increased the total number of bunching cells from 1.5 to 2.5. In this paper, we describe design concepts and detailed optimization processes of a 3 MeV linac with the 2.5 bunching cells to optimize RF parameters such as the quality factor, resonance frequency, and uniformity of electric field distribution along the linac. Lastly, we will discuss the application of 3 MeV linac.

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reference for this paper ※ https://doi.org/10.18429/JACoW-IPAC2019-WEPRB055

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paper received ※ 04 June 2019 paper accepted ※ 16 June 2019 issue date ※ 21 June 2019

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WEPRB056

Design Study of 325MHz RF Power Coupler for Superconducting Cavity

cavity, impedance, superconducting-cavity, resonance

2937

J.Y. Yoon, H.J. Cha, S.W. Jang, E.-S. Kim, K.R. Kim, C.S. Park, S.H. Park
KUS, Sejong, Republic of Korea
J. Bahng
Korea University Sejong Campus, Sejong, Republic of Korea
K.R. Kim
PAL, Pohang, Kyungbuk, Republic of Korea

We present the design study of the RF input power coupler for 325 MHz superconducting cavities. The power coupler, based on a conventional coaxial transmission line, provides RF powers to the cavity up to 12kW in CW mode. The thermal interceptors are considered as 4.5 K and 40 K or 4.5 K and 77 K corresponding to the usage of liquid Helium only or both liquid Helium and Nitrogen for cryogenic temperature to reduce the thermal load. The transition box (T-box), which is assembled with power coupler, is designed and applied for impedance matching and inner conductor cooling.

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reference for this paper ※ https://doi.org/10.18429/JACoW-IPAC2019-WEPRB056

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paper received ※ 14 May 2019 paper accepted ※ 23 May 2019 issue date ※ 21 June 2019

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WEPRB058

Combined Field Emission and Multipactor Simulation in High Gradient RF Accelerating Structures

electron, multipactoring, cavity, GUI

2940

D. Banon-Caballero
IFIC, Valencia, Spain
N. Catalán Lasheras, K.T. Szypula, W. Wuensch
CERN, Geneva, Switzerland
A. Faus-Golfe
LAL, Orsay, France
B. Gimeno
UVEG, Burjasot (Valencia), Spain

Field emitted electrons have important consequences in the operation of high-gradient RF accelerating structures both by generating so-called dark currents and initiating RF breakdown. The latter is an important limitation of the performance in such devices. Another kind of vacuum discharge that primarily affects the operation of lower-field RF components, for example those used in space applications, is multipactor. Theoretical simulations using CST Particle Studio, show that field emitted electrons generated in the high field regions of high-gradient accelerating cavities migrate to low field regions under ponderomotive forces potentially triggering multipactor there. This phenomenon is an interplay between high field and low field processes which may have as a consequence that multipactor actually affects to the performance of high-gradient cavities because field emitted electrons might reduce the timescales for the onset of multipactor.

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reference for this paper ※ https://doi.org/10.18429/JACoW-IPAC2019-WEPRB058

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paper received ※ 27 April 2019 paper accepted ※ 21 May 2019 issue date ※ 21 June 2019

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WEPRB060

HOM Damped Normal Conducting 1.5 GHz Cavity Design Evolution for the 3rd Harmonic System of the ALBA Storage Ring

cavity, GUI, HOM, insertion

2948

A. Salom, J.M. Alvarez, B. Bravo, F. Pérez
ALBA-CELLS Synchrotron, Cerdanyola del Vallès, Spain

In a collaboration framework with CERN, ALBA has designed a normal conducting active 1.5 GHz cavity which could serve as main RF system for the Damping Ring of CLIC and as an active third harmonic cavity for the ALBA Storage Ring. The third harmonic cavity at ALBA will be used to increase the bunch length in order to improve the beam lifetime and increase the beam stability thresholds. The main advantage of an active third harmonic cavity is that optimum conditions can be reached for any beam current. This paper presents the evolution of the preliminary design of this cavity and its trans-dampers: high order modes coaxial dampers with waveguide transitions to N, which allows extracting the power of the high order modes induced by the beam outside of the cavity and to dissipate it using standard loads. This approach has two main advantages: no ferrites brazing is needed and they provide a diagnostic to analyze the beam dynamics. The new features of the design, together with electromagnetic simulations, mechanical and thermal stress analysis will be presented in this paper as well as the first stages of the prototype production status.

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reference for this paper ※ https://doi.org/10.18429/JACoW-IPAC2019-WEPRB060

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paper received ※ 15 May 2019 paper accepted ※ 23 May 2019 issue date ※ 21 June 2019

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WEPRB064

High Power Conditioning of X-Band Variable Power Splitter and Phase Shifter

klystron, GUI, ISOL, operation

2964

V. del Pozo Romano, H. Bursali, N. Catalán Lasheras, A. Grudiev, S. Pitman, I. Syratchev
CERN, Meyrin, Switzerland
C. Serpico
Elettra-Sincrotrone Trieste S.C.p.A., Basovizza, Italy
M. Volpi
The University of Melbourne, Melbourne, Victoria, Australia

The three X-band test facilities currently at CERN aim at qualifying CLIC structures prototypes but are also exten- sively used to qualify X-band components operation at high power. In order to upgrade one of the facilities from a single test line to a double test line facility, a high power variable splitter and variable phase shifter have been designed and manufactured at CERN. They have been power tested, ﬁrst in a dedicated test and also in their ﬁnal conﬁguration, to en- sure stable power operation before installing them together with an accelerating structure. In this paper, we broadly describe the RF and mechanical design, manufacturing and low power measurements agreement with simulations. We report the high power qualiﬁcation of both components and their suitability to be used in existing and planned X-band facilities.

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reference for this paper ※ https://doi.org/10.18429/JACoW-IPAC2019-WEPRB064

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paper received ※ 10 May 2019 paper accepted ※ 22 May 2019 issue date ※ 21 June 2019

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WEPRB080

Optimization of RF Cavities Using MOGA for ALS-U

cavity, impedance, controls, gun

3007

H.Q. Feng, K.M. Baptiste, D. Li, T.H. Luo
LBNL, Berkeley, California, USA
H.Q. Feng, W.-H. Huang, Z.N. Liu, C.-X. Tang
TUB, Beijing, People’s Republic of China

Funding: Director of Office of Science of the U.S. Department of Energy under Contract No. DE-AC02-05CH11231
A multi-objective genetic algorithm-based optimiza-tion process has been applied to optimize the RF design of a 500 MHz main cavity and a 1.5 GHz Higher Harmon-ic Cavity (HHC) for the Advanced Light Source upgrade (ALS-U) in Lawrence Berkeley National Laboratory (LBNL). For the main cavity, a significant improvement, compared with the existing ALS cavity, has been achieved in cavity shunt impedance and power loss den-sity simultaneously. The field strengths and distribution of the optimized structure are analysed for further re-search. For the HHC, a cavity with low R/Q has been pre-liminary designed to mitigate the beam instability. This study also serves as an example of how a genetic algo-rithm can be used for optimizing RF cavities.

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reference for this paper ※ https://doi.org/10.18429/JACoW-IPAC2019-WEPRB080

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paper received ※ 16 May 2019 paper accepted ※ 22 May 2019 issue date ※ 21 June 2019

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WEPRB081

Design Study on Higher Harmonic Cavity for ALS-U

cavity, impedance, higher-order-mode, wakefield

3011

H.Q. Feng, K.M. Baptiste, S. De Santis, D. Li, T.H. Luo
LBNL, Berkeley, California, USA
H.Q. Feng, W.-H. Huang, Z.N. Liu, C.-X. Tang
TUB, Beijing, People’s Republic of China

Funding: Director of Office of Science of the U.S. Department of Energy under Contract No. DE-AC02-05CH11231
The ALS upgrade (ALS-U) to a diffraction-limited light source [1] depends on the ability to lengthen the stored bunches to limit the emittance growth and increase the beam life time. Higher harmonic cavities (HHCs), also known as Landau cavities, have been proposed to in-crease beam lifetime and Landau damping by lengthen-ing the bunch. We present an optimized 1.5 GHz normal conducting HHC design for the ALS-U with a supercon-ducting-like geometry using multi-objective genetic algorithm (MOGA) for lower R/Q. The optimization goal is to reach the required shunt impedance while maintain-ing a relatively high Q value of the cavities. To minimize the coupled bunch instabilities, higher-order mode (HOM) of the HHC as well as corresponding impedance are explored and characterized.

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reference for this paper ※ https://doi.org/10.18429/JACoW-IPAC2019-WEPRB081

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paper received ※ 16 May 2019 paper accepted ※ 21 May 2019 issue date ※ 21 June 2019

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WEPRB095

Microbunching Plasma-Cascade Instability

plasma, electron, bunching, focusing

3035

V. Litvinenko
Stony Brook University, Stony Brook, USA
T. Hayes, Y.C. Jing, D. Kayran, J. Ma, T.A. Miller, G. Narayan, I. Pinayev, F. Severino, G. Wang
BNL, Upton, Long Island, New York, USA
I. Petrushina
SUNY SB, Stony Brook, New York, USA
K. Shih
SBU, Stony Brook, New York, USA

Funding: Work supported by Brookhaven Science Associates, LLC under Contract No. DE-AC02-98CH10886 with the U.S. Department of Energy and NSF Grant No. PHY-141525
We present a new type of longitudinal microbunching instability entitled ’Plasma-Cascade Instability’. This instability could occur in beams propagating along a straight section with external focusing elements. We present a theoretical description of this instability as well as self-consistent 3D simulations. Finally, we present results of experimental observation of Plasma-Cascade Instability at frequencies up to 10 THz using SRF linear accelerator built for Coherent electron Cooling experiment *.
* Commissioning of FEL-based Coherent electron Cooling system, V.N. Litvinenko et al., In proc. of 38th Int. Free Electron Laser Conf.(FEL’17), Santa Fe, NM, USA, August 20-25, 2017, p. 132

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reference for this paper ※ https://doi.org/10.18429/JACoW-IPAC2019-WEPRB095

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paper received ※ 18 May 2019 paper accepted ※ 23 May 2019 issue date ※ 21 June 2019

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WEPRB099

Status Update of a Harmonic Kicker Development for JLEIC

kicker, multipole, cavity, coupling

3047

G.-T. Park, J. Guo, J. Henry, M. Marchlik, F. Marhauser, R.A. Rimmer, H. Wang, S. Wang
JLab, Newport News, Virginia, USA

Funding: Authored by Jefferson Science Associates, LLC under U.S. DOE Contract No. DE-AC05-06OR23177.
An effort to develop the second prototype of the harmonic kicker for the Circulator Cooler Ring (CCR) of the Jefferson Lab Electron-Ion Collider (JLEIC) is under way. After beam dynamics studies and completion of a conceptual RF design of the kicker [1], further progress has been made toward the final mechanical design including the input power coupler (loop) design, tuner ports, multipacting studies. Furthermore, concerning the kicker’s compatibility with beam dynamics, the impact of RF multipole components was investigated and a scheme was developed to cancel out detrimental beam effects.
1. G. Park, et al, The Development of a New Fast Harmonic Kicker for the JLEIC Circulator Cooler Ring, TUPAL068, proceedings of IPAC 2018.

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reference for this paper ※ https://doi.org/10.18429/JACoW-IPAC2019-WEPRB099

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paper received ※ 15 May 2019 paper accepted ※ 23 May 2019 issue date ※ 21 June 2019

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WEPRB105

Design of an X-Band Constant Impedance LINAC for Compact Light Project

linac, quadrupole, impedance, framework

3055

J.M. Arnesano, A. Mostacci, L. Palumbo
Sapienza University of Rome, Rome, Italy
M. Diomede, M. Marongiu
INFN/LNF, Frascati, Italy
L. Ficcadenti
INFN-Roma, Roma, Italy

Within the framework of Horizon 2020 project, Compact Light, in order to provide a high performance, high-gradient X-band technology, for the new generation of hard X-ray FEL, a travelling wave (TW) Linac, working on 2pi/3 mode at 11.9952 GHz, fed by two types of asymmetrically couplers, has been designed. The design was performed using CST Microwave Studio frequency domain solver. First, simulations have been conduct in order to obtain the best trade-off between single cell’s parameters, varying iris aperture. Then, the both couplers, with and without pumping port, has been tuned to avoid reflections at the input port. Finally, the entire structure, with 5 cells, was simulated. The main structure parameters will be present and we will also show and discuss the acceleranting gradient obtained vary with linac lenght and input power.

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reference for this paper ※ https://doi.org/10.18429/JACoW-IPAC2019-WEPRB105

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paper received ※ 15 May 2019 paper accepted ※ 24 May 2019 issue date ※ 21 June 2019

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WEPRB106

Simulation of the Transition Radiation Transport Through an Optic System

radiation, electron, optics, diagnostics

3059

M. Marongiu, A. Mostacci, L. Palumbo
Sapienza University of Rome, Rome, Italy
F.G. Bisesto, E. Chiadroni, G. Di Pirro, G. Franzini, A. Giribono, V. Shpakov, A. Stella, A. Variola
INFN/LNF, Frascati, Italy
A. Cianchi
Università di Roma II Tor Vergata, Roma, Italy
A. Mostacci, L. Palumbo
INFN-Roma, Roma, Italy

Optical Transition Radiation (OTR) screens are widely used for beam profile measurements. The radiation is emitted when a charged particle beam crosses the boundary between two media with different optical properties. The main advantages of OTR are the instantaneous emission process allowing fast single shot measurements (i.e. bunch by bunch measurements in a multi bunch machine), and the good linearity with the beam charge (if coherent effects can be neglected). Furthermore, OTR angular distribution strongly depends on beam energy. Since OTR screens are typically placed in several positions along the Linac to monitor beam envelope, one may perform a distributed energy measurement along the machine: this will be useful, for instance, during the commissioning phase of a machine. This paper deals with the studies of an algorithm to optimize the generation and the transport of the transition radiation through an optic system using the simulation tool Zemax. The algorithm, in combination with a particle tracking code (i.e. Elegant), will allow to simulate the radiation generated by a beam and, so, to take into account beam divergence and energy spread or chromatic effects in the optic system.

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reference for this paper ※ https://doi.org/10.18429/JACoW-IPAC2019-WEPRB106

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paper received ※ 08 May 2019 paper accepted ※ 21 May 2019 issue date ※ 21 June 2019

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WEPTS002

Study of a Proton Therapy Beamline for Eye Treatment with Beam Delivery Simulation (BDSIM) and an In-House Tracking Code

scattering, proton, neutron, site

3088

E. Gnacadja, C. Hernalsteens, N. Pauly, R. Tesse
ULB - FSA - SMN, Bruxelles, Belgium
S.T. Boogert, L.J. Nevay, W. Shields
JAI, Egham, Surrey, United Kingdom

The complete modelling of passive scattering proton therapy systems is challenging and requires simulation tools that have capabilities in both beam transport and in the detailed description of particle-matter interactions. Beam Delivery Simulation (BDSIM) allows the seamless simulation of the transport of particles in a beamline and its surrounding environment. A complete 3D model can be built from Geant4, CLHEP and ROOT to provide a complete analysis of the primary beam tracking. This capability is applied to the eye treatment proton therapy machine part of the IBA Proteus Plus product line. Those simulations are compared with a fast in-house particle tracking code with a semi-analytical model of Multiple Coulomb Scattering. The preliminary results leading to the detailed knowledge of the beamline performance are discussed in detail.

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reference for this paper ※ https://doi.org/10.18429/JACoW-IPAC2019-WEPTS002

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paper received ※ 15 May 2019 paper accepted ※ 23 May 2019 issue date ※ 21 June 2019

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WEPTS011

Intra-Beam Scattering Effect in the SOLEIL Storage Ring Upgrade

emittance, lattice, coupling, cavity

3106

A. Vivoli, A. Bence, P. Brunelle, A. Gamelin, L. Hoummi, A. Loulergue, L.S. Nadolski, R. Nagaoka, M.-A. Tordeux
SOLEIL, Gif-sur-Yvette, France

As the work on the design of the upgrade of SOLEIL storage ring advances, the study of the impact of Intra-Beam Scattering (IBS) on the equilibrium emittance is also progressing, showing a significant contribution of this effect. Different measures can be taken to mitigate the emittance dilution, like operating the machine with full transverse coupling and using harmonic cavities to increase bunch length. The calculation of the IBS effect needs then to take into account the different beam dynamics and its effect on the particle distribution. In this paper the current state of the ongoing study is presented, reporting on the results obtained for the different options considered, and comparing the results of different codes and their implicit assumptions.

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reference for this paper ※ https://doi.org/10.18429/JACoW-IPAC2019-WEPTS011

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paper received ※ 14 May 2019 paper accepted ※ 18 May 2019 issue date ※ 21 June 2019

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WEPTS012

RF Design Studies of a 1.3 GHz Normal Conducting CW Buncher for European X-FEL

multipactoring, impedance, coupling, cavity

3109

S. Lal, Y. Chen, H.J. Qian, H. Shaker, G. Shu, F. Stephan
DESY Zeuthen, Zeuthen, Germany
V.V. Paramonov
RAS/INR, Moscow, Russia

A CW upgrade of European XFEL is under consideration, and CW electron injector is under R&D at DESY. One of the injector solutions is the LCLS-II like injector based on a normal conducting CW gun and buncher. RF design of a 1.3 GHz normal conducting buncher structure with accelerating voltage of ~ 400 kV, for such a CW injector is carried out at DESY Zeuthen site. The buncher structures with different geometrical shapes and numbers of cells are studied. The designs are optimized to have higher shunt impedance, higher mode separation and lower thermal power density for CW operation. Multipacting analysis and beam dynamics simulations are also presented.

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reference for this paper ※ https://doi.org/10.18429/JACoW-IPAC2019-WEPTS012

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paper received ※ 12 May 2019 paper accepted ※ 22 May 2019 issue date ※ 21 June 2019

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WEPTS015

Synchronous Measurements of Electron Bunches Under the Influence of the Microbunching Instability

synchrotron, radiation, bunching, storage-ring

3119

M. Brosi, T. Boltz, E. Bründermann, S. Funkner, B. Kehrer, A.-S. Müller, M.J. Nasse, G. Niehues, M.M. Patil, P. Schreiber, P. Schönfeldt, J.L. Steinmann
KIT, Karlsruhe, Germany

Funding: This work has been supported by the German Federal Ministry of Education and Research (Grant No. 05K16VKA). We acknowledge the support by the Helmholtz International Research School for Teratronics.
The microbunching instability is a longitudinal collective instability which occurs for short electron bunches in a storage ring above a certain threshold current. The instability leads to a charge modulation in the longitudinal phase space. The resulting substructures on the longitudinal bunch profile vary over time and lead to fluctuations in the emitted power of coherent synchrotron radiation (CSR). To study the underlying longitudinal dynamics on a turn-by-turn basis, the KIT storage ring KARA (Karlsruhe Research Accelerator) provides a wide variety of diagnostic systems. By synchronizing the single-shot electro-optical spectral decoding setup (longitudinal profile), the bunch-by-bunch THz detection systems (THz power) and the horizontal bunch size measurement setup (energy spread), three important properties of the bunch during this instability can be measured at every turn for long time scales. This allows a deep insight into the dynamics of the bunch under the influence of the microbunching instability. This contribution will discuss effects like the connection between the emitted CSR power and the deformations in the longitudinal bunch profile on the time scale of the instability.

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paper received ※ 14 May 2019 paper accepted ※ 20 May 2019 issue date ※ 21 June 2019

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WEPTS016

Longitudinal Beam Manipulation by RF Phase Modulation at the Karlsruhe Research Accelerator

experiment, synchrotron, cavity, beam-loading

3123

A. Mochihashi, E. Blomley, T. Boltz, E. Huttel, B. Kehrer, A.-S. Müller, M. Schuh
KIT, Karlsruhe, Germany
D. Teytelman
Dimtel, San Jose, USA

At the storage ring KARA (Karlsruhe Research Accelerator) of the Karlsruhe Institute of Technology (KIT) we have installed a function for the RF phase modulation to the low-level RF system. By choosing proper conditions of the modulation, the electron distribution on the longitudinal phase space can be changed in a large range. There are several applications of this longitudinal manipulation to the accelerator operation: an improvement of the beam lifetime and suppression of collective instabilities. We have performed tracking simulations for the longitudinal beam manipulation by the RF phase modulation. The results have implied that the longitudinal phase space distribution strongly depends on the modulation frequency. We have also performed experiments, which aimed at improving the beam lifetime in 2.5 GeV KARA multi-bunch operations. In this contribution, the low-level RF system at KARA, the simulation and experimental results under the RF phase modulation will be presented. As one of the options of the modulation, we consider manipulation of the internal fine structure in the longitudinal phase space by the modulation.

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reference for this paper ※ https://doi.org/10.18429/JACoW-IPAC2019-WEPTS016

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paper received ※ 15 May 2019 paper accepted ※ 23 May 2019 issue date ※ 21 June 2019

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WEPTS017

Synchrotron Radiation Module in OCELOT Toolkit

electron, undulator, radiation, FEL

3127

S. Tomin, G. Geloni
EuXFEL, Hamburg, Germany

Synchrotron radiation (SR) sources based on single-pass accelerators (e.g. linacs, plasma accelerators) have to cope with electron beams with a rather complicated phase space distribution. In this case, the convolution method usually employed to calculate radiation properties can give poor accuracy or be not applicable at all. Moreover, dynamical effects can also play a role in the emission mechanism. This happens when the beam parameters (e.g. beam current) significantly change during the passage through the undulator. In this work, we present a dedicated SR module of the OCELOT toolkit, which is well suited to deal with these situations.

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reference for this paper ※ https://doi.org/10.18429/JACoW-IPAC2019-WEPTS017

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paper received ※ 13 May 2019 paper accepted ※ 23 May 2019 issue date ※ 21 June 2019

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WEPTS024

Tune Shifts and Optics Modulations in the High Intensity Operation at J-PARC MR

space-charge, betatron, sextupole, quadrupole

3148

T.Y. Yasui
The University of Tokyo, Graduate School of Science, Tokyo, Japan
S. Igarashi, T. Koseki, K. Ohmi, Y. Sato, K. Satou
KEK, Ibaraki, Japan

Funding: This study is supported by the MEXT program "Advanced Leading Graduate Course for Photon Science (ALPS)"
J-PARC Main Ring (MR) is the intensity-frontier proton accelerator. The beam intensity of 2.6×10¹⁴ protons per pulse has been achieved for the current user operation. In this high-intensity operation, the tune spread caused by the space-charge is one of the main reasons for beam loss. The modulation of the betatron function and the tune shift were simulated with a PIC algorithm calculation code*. The simulation results showed that the space-charge effects were dominant in small particle action, and the sextupole fields effects were dominant in large particle action. Because sextupole strength is large in MR, sextupole fields induce substantial tune shifts. At the benchmark of the space-charge simulation, the simulation results matched the analytical space-charge calculations performed without sextupoles. It was found that the betatron function was modulated at most 6% by the space-charge effects and at most 8% by the effects of sextupoles in J-PARC MR. These effects to the injection beam optics matching and to the beam aperture will be investigated.
* K. Ohmi et al., "Study of Halo Formation in J-PARC MR", Proceedings of the 22nd Particle Accelerator Conf. (PAC’07), Albuquerque, NM, USA, Jun. 2007, paper THPAN040, pp. 3318-3320.

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paper received ※ 15 May 2019 paper accepted ※ 21 May 2019 issue date ※ 21 June 2019

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WEPTS025

MiniScatter, a Simple Geant4 Wrapper

target, detector, interface, plasma

3152

K.N. Sjobak, H. Holmestad
University of Oslo, Oslo, Norway

Funding: Research Council of Norway, project 255196
In order to estimate what happens to particle beams when they hit windows, gas, and various other targets, a simple tool has been developed based on Geant4. This tool wraps geometry setup, primary beam generation from Twiss parameters, visualization, and automatic analysis and plots in a simple-to-use command-line tool. Furthermore, a Jupyter-friendly Python interface for running simulations and parallelized parameter scans is included. The code, its interface, and a few selected examples will be presented.

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reference for this paper ※ https://doi.org/10.18429/JACoW-IPAC2019-WEPTS025

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paper received ※ 14 May 2019 paper accepted ※ 22 May 2019 issue date ※ 21 June 2019

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WEPTS033

A High-performance Code for Beam Dynamics Simulation of Synchrotrons

extraction, synchrotron, sextupole, proton

3170

H.J. Yao, X. Guan, G.R. Li, P.F. Ma, X.W. Wang, Q. Zhang, S.X. Zheng
TUB, Beijing, People’s Republic of China

This paper introduces a high-performance code Li-track for beam dynamics simulation of synchrotrons. It is a parallel multi-particle tracking program written entirely in C++ and therefore has a high computational speed. The overall design of Li-track is based on object-oriented mode, and the implemented element model can be easily reused to build different synchrotron lattice. The symplectic integral algorithm is used to ensure there are no physical errors in a long-term simulation. This code has been used for the slow extraction simulation of XiPAF synchrotron and the results will be given in this paper.

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reference for this paper ※ https://doi.org/10.18429/JACoW-IPAC2019-WEPTS033

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paper received ※ 30 April 2019 paper accepted ※ 23 May 2019 issue date ※ 21 June 2019

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WEPTS034

Generation of Sub-Femtosecond Electron Beams and Electron Bunch Trains With High Form Factor Using Wake Field Structures

electron, wakefield, bunching, space-charge

3174

Z. Dong, H. Chen, X.J. Deng, Y.C. Du, Z. Zhou
TUB, Beijing, People’s Republic of China

In this paper, we propose two beam manipulation methods with wakefield structures in a photo-injector. First, we propose a simple scheme to compensate non-linear effects during ballistic bunching by using a wakefield structure. Simulations have shown beams of 1 pC charge can be compressed to 1.56 fs rms, and even shorter beams (a few hundred attoseconds) can be obtained with bunch charge well below 1 pC. In the second part, a method of producing bunch trains with high form factor is proposed by using multiple wake-field structures. Simulation results have shown the production of a train with a form factor of 0.5 using a 1 nC beam at few-MeV energy.

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reference for this paper ※ https://doi.org/10.18429/JACoW-IPAC2019-WEPTS034

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paper received ※ 11 May 2019 paper accepted ※ 23 May 2019 issue date ※ 21 June 2019

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WEPTS037

DC Beam Space-Charge Modeling for OpenXAL

space-charge, LEBT, solenoid, GUI

3177

B.E. Bolling, N. Milas
ESS, Lund, Sweden

OpenXAL is an open source multi-purpose accelerator physics software platform based on a pure Java open source development environment used for creating accelerator physics applications, scripts and services. Currently, the software has been used with an ellipsoidal (bunched) beam to account for space-charge effects. Applications developed so far for ESS, such as the Virtual Machine for the ESS Low Energy Beam Transport (LEBT) section, would profit from a DC beam description. In this paper, the space-charge component for a continuous beam is derived taking into account beams with different transverse charge distributions (uniform, gaussian, etc). The implementation in OpenXAL and a comparison with other simulation codes is also presented.

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reference for this paper ※ https://doi.org/10.18429/JACoW-IPAC2019-WEPTS037

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paper received ※ 14 May 2019 paper accepted ※ 20 May 2019 issue date ※ 21 June 2019

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WEPTS038

New RFQ and Field Map Model for the ESS Linac Simulator

rfq, linac, space-charge, cavity

3181

J.F. Esteban Müller, E. Laface
ESS, Lund, Sweden

The Java ESS Linac Simulator (JELS) is an extension of the Open XAL online model that is a fundamental part of the accelerator control system. The model is used by high-level physics applications for commissioning, tuning, and machine development activities at the European Spallation Source (ESS). This paper summarizes the upgrades done to JELS during the last year. An RFQ model is under development. The RFQ was the only element of the linac missing in the online model. The electromagnetic field map model has been refactored to ease implementation of new elements (rf cavities and magnets), and to allow the superposition of more than one field map and other elements. Further improvements have also been done in the treatment of corrector magnets and space charge for continuous beam in the Low-Energy Beam Transport (LEBT). Finally, the machine description can now include arbitrary aperture definitions.

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reference for this paper ※ https://doi.org/10.18429/JACoW-IPAC2019-WEPTS038

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paper received ※ 14 May 2019 paper accepted ※ 22 May 2019 issue date ※ 21 June 2019

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WEPTS039

Momentum Slip-Stacking in CERN SPS for the Ion Beams

cavity, optics, operation, emittance

3184

T. Argyropoulos, T. Bohl, A. Lasheen, G. Papotti, D. Quartullo, E.N. Shaposhnikova
CERN, Geneva, Switzerland

The LHC Injectors Upgrade (LIU) project at CERN aims at doubling the total intensity of the lead ion beam for the High-Luminosity (HL) LHC. Achieving this goal requires using momentum slip-stacking in the SPS, the LHC injector. Slip-stacking will be applied on an intermediate energy plateau to interleave two batches, reducing the bunch spacing from 100 ns to 50 ns and thus increasing the total number of bunches injected into the LHC. Realistic macro-particle simulations, with the present SPS impedance model are used to study and design this complicated beam manipulation. Slip-stacking can be tested experimentally only after the upgrade of the SPS 200 MHz RF system, in 2021. Preliminary, slip-stacking related beam measurements were performed at the end of 2018. In this paper both macro-particle simulations and beam measurements are reported with emphasis given on optimisation of the process, crucial to achieve the required HL-LHC parameters (bunch lengths, beam losses).

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reference for this paper ※ https://doi.org/10.18429/JACoW-IPAC2019-WEPTS039

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paper received ※ 15 May 2019 paper accepted ※ 23 May 2019 issue date ※ 21 June 2019

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WEPTS042

Detailed Characterisation of the LEIR Intensity Limitations for a Pb Ion Beam

emittance, resonance, injection, sextupole

3196

Á. Saá Hernández, H. Bartosik, N. Biancacci, S. Hirlaender, D. Moreno Garcia, M. Zampetakis
CERN, Meyrin, Switzerland

The equilibrium emittance of the Pb beam in the CERN Low Energy Ion Ring (LEIR) results from the interplay of electron cooling and heating processes, as intra-beam scattering and space charge. In this paper we present the measurements of the emittance evolution as a function of intensity, working point and resonance excitation, and compare them with the simulations of the heating processes. Optimum settings for normal and skew sextupoles have been found for the compensation of resonances excited by the lattice.

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reference for this paper ※ https://doi.org/10.18429/JACoW-IPAC2019-WEPTS042

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paper received ※ 18 April 2019 paper accepted ※ 22 May 2019 issue date ※ 21 June 2019

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WEPTS043

SixTrack Version 5: Status and New Developments

electron, scattering, collimation, HOM

3200

R. De Maria, J. Andersson, L. Field, M. Giovannozzi, P.D. Hermes, N. Hoimyr, G. Iadarola, S. Kostoglou, E.H. Maclean, E. McIntosh, A. Mereghetti, J. Molson, V.K.B. Olsen, D. Pellegrini, T. Persson, M. Schwinzerl
CERN, Geneva, Switzerland
B. Dalena, T. Pugnat
CEA-IRFU, Gif-sur-Yvette, France
K.N. Sjobak
University of Oslo, Oslo, Norway
I. Zacharov
EPFL, Lausanne, Switzerland

SixTrack Version 5 is a major SixTrack release that introduces new features, with improved integration of the existing ones, and extensive code restructuring. New features include dynamic-memory management, scattering-routine integration, a new initial-condition module, and reviewed post-processing methods. Existing features like on-line aperture checking and Fluka-coupling are now enabled by default. Extensive performance regression tests have been developed and deployed as part of the new-release generation. The new features of the tracking environment developed for the massive numerical simulations will be discussed as well.

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reference for this paper ※ https://doi.org/10.18429/JACoW-IPAC2019-WEPTS043

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paper received ※ 17 April 2019 paper accepted ※ 22 May 2019 issue date ※ 21 June 2019

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WEPTS044

Instability Latency in the LHC

octupole, experiment, feedback, damping

3204

S.V. Furuseth, D. Amorim, S.A. Antipov, X. Buffat, N. Mounet, E. Métral, B. Salvant
CERN, Geneva, Switzerland
S.V. Furuseth, T. Pieloni, C. Tambasco
EPFL, Lausanne, Switzerland

The Large Hadron Collider (LHC) has experienced multiple instabilities that occur between minutes and hours after the last modification of the machine settings. The existence of instabilities with high latency has been reproduced also in simulations. Dedicated experiments, injecting a controlled noise into the beam, have now been performed to discover the dependence of this latency on key parameters. The results seem compatible with a mechanism linked to a steady and slow modification of the transverse beam distribution leading to a loss of Landau damping.

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reference for this paper ※ https://doi.org/10.18429/JACoW-IPAC2019-WEPTS044

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paper received ※ 30 April 2019 paper accepted ※ 21 May 2019 issue date ※ 21 June 2019

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WEPTS045

High-Performance Scheduling of Multi-Beam Multi-Bunch Simulations

wakefield, collider, site, hadron

3208

S.V. Furuseth, X. Buffat
CERN, Geneva, Switzerland
S.V. Furuseth
EPFL, Lausanne, Switzerland

Coherent multi-bunch interactions through beam-beam forces or wake fields can cause severe impacts on the beams in circular colliders, if not well understood and countered for. COMBI is a parallel multiparticle tracking code developed to study such interactions. Its implementation greatly limits its efficiency when considering realistic configurations featuring effects with different computational requirements, such as the multi-bunch interaction through wake fields, beam-beam interactions, transverse feedback and lattice non-linearities. A new parallel scheduling method, pipelining the effects for each bunch, has greatly sped up the code. The new version of the code, COMBIp, is presented here.

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reference for this paper ※ https://doi.org/10.18429/JACoW-IPAC2019-WEPTS045

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paper received ※ 06 May 2019 paper accepted ※ 21 May 2019 issue date ※ 21 June 2019

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WEPTS047

Space Charge Driven Resonances in the CERN PS

resonance, space-charge, brightness, lattice

3216

F. Asvesta
NTUA, Athens, Greece
H. Bartosik, A. Huschauer, Y. Papaphilippou
CERN, Geneva, Switzerland

In the CERN Proton Synchrotron space charge driven resonances are excited around the operational working point due to the periodicity of the optics functions. In this paper, the resonances are studied using analytical methods, i.e. the evaluation of the resonance driving terms connected to the space charge potential of Gaussian distributions. Furthermore, the resonances are characterized in measurements and simulations for various beams. The beams considered are different in terms of brightness, in order to study the dependence of the resonance strength on the space charge force.

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reference for this paper ※ https://doi.org/10.18429/JACoW-IPAC2019-WEPTS047

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paper received ※ 17 April 2019 paper accepted ※ 21 May 2019 issue date ※ 21 June 2019

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WEPTS048

Electron Beam Dynamics Simulation for Electron Lenses

electron, gun, cathode, experiment

3220

S. Sadovich, A. Rossi
CERN, Meyrin, Switzerland
G. Stancari
Fermilab, Batavia, Illinois, USA

A test stand is under construction at CERN to study high perveance electron guns, electron beam dynamics, and electron beam diagnostics for electron lenses. It will be used to test electron guns for the Hollow Electron Lenses under consideration for beam halo control for High Luminosity LHC (CERN), and for the Space Charge Compensation at SIS18 (GSI) in the frame of the EU funded ARIES project. In order to prepare for this test stand, simulations will be presented and compared with experiments undertaken at the Fermilab (FNAL) electron lens test stand. These were conducted using a hollow electron gun, with the magnetic field configuration and beam current varied to study their effect. The impact of imperfections on the beam dynamics and overall quality of the electron beam will be discussed. A method for comparing experimental data with simulation is also presented to allow bench-marking of the computer models and simulation tools that will later be applied to the analysis of measurements performed at CERN.

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reference for this paper ※ https://doi.org/10.18429/JACoW-IPAC2019-WEPTS048

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paper received ※ 15 May 2019 paper accepted ※ 23 May 2019 issue date ※ 21 June 2019

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WEPTS049

Flat-Bottom Instabilities in the CERN SPS

impedance, HOM, feedback, LLRF

3224

M. Schwarz, K. Iliakis, A. Lasheen, G. Papotti, J. Repond, E.N. Shaposhnikova, H. Timko
CERN, Meyrin, Switzerland

At beam intensities of 2.6·10¹¹ protons per bunch, required at SPS injection for the High Luminosity LHC beam, longitudinal instabilities can degrade the beam quality delivered by the SPS, the LHC injector at CERN. In this paper, we concentrate on beam instability at flat bottom. The dependence of the instability threshold on longitudinal emittance and LLRF system settings was measured, to help identify the impedance driving this instability. While reducing the longitudinal emittance reduces the losses at injection, it can drive the beam unstable. The LLRF system of the SPS (partially) compensates beam loading, but also affects the instability. The effect of the different LLRF systems (feedback, feedforward, phase loop and longitudinal damper) and fourth harmonic RF system on the instability was investigated. The measurements are compared with simulations performed with the longitudinal tracking code BLonD.

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reference for this paper ※ https://doi.org/10.18429/JACoW-IPAC2019-WEPTS049

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paper received ※ 10 May 2019 paper accepted ※ 19 May 2019 issue date ※ 21 June 2019

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WEPTS050

Multi-Species Electron-Ion Simulations and their Application to the LHC

electron, operation, beam-losses, space-charge

3228

L. Mether, G. Iadarola, K.L. Poland, G. Rumolo, G. Skripka
CERN, Meyrin, Switzerland

During operation in 2017 and 2018, the LHC suffered from recurrent beam aborts associated with beam losses in one of its arc cells in correlation with quickly developing transverse coherent oscillations. The events are thought to have been caused by a localised high gas density resulting from the phase transition of a macro-particle that has entered the beam. In order to model the observed coherent effects through the interaction of the beam with the induced pressure bump, novel modelling capabilities have been implemented that allow for the simulation of multiple clouds of different particle species and their interaction with the beam. In this contribution the simulation model and its application are described.

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reference for this paper ※ https://doi.org/10.18429/JACoW-IPAC2019-WEPTS050

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paper received ※ 13 May 2019 paper accepted ※ 21 May 2019 issue date ※ 21 June 2019

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WEPTS051

Comparison of Electron Cloud Build-Up Simulations Against Heat Load Measurements for the LHC Arcs With Different Beam Configurations

electron, operation, synchrotron-radiation, radiation

3232

G. Skripka, G. Iadarola, L. Mether, G. Rumolo, E.G.T. Wulff
CERN, Meyrin, Switzerland
P. Dijkstal
PSI, Villigen PSI, Switzerland

Electron cloud effects are among the main performance limitations for the operation of the Large Hadron Collider (LHC) with 25 ns bunch spacing. A large number of electrons impacting on the beam screens of the cold magnets induces significant heat load, reaching values close to the full cooling capacity available from the cryogenic system. Interestingly, it is observed that parts of the machine that are by design identical show very different heat loads. We used numerical simulations to investigate the possibility that these differences are induced by different surface properties, in particular maximum Secondary Electron Yield (SEY) for the different cryomagnets. Using the PyECLOUD code, the electron cloud build-up was simulated assuming different values of SEY in the LHC cold magnets. Comparing the measured heat loads to the simulation results for the 25 ns beams at 450 GeV we have identified the SEY values that match the observations in these conditions. These SEY values were found to be in good agreement with the heat loads measured with different beam configurations (changing the bunch pattern, the bunch intensity and the beam energy).

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reference for this paper ※ https://doi.org/10.18429/JACoW-IPAC2019-WEPTS051

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paper received ※ 13 May 2019 paper accepted ※ 22 May 2019 issue date ※ 21 June 2019

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WEPTS052

Electron Cloud Build-Up Simulations in the Two-Beam Common Chamber of the HL-LHC TDIS With Nonuniform Surface Properties

electron, injection, vacuum, operation

3236

G. Skripka, C. Bracco, G. Iadarola, A. Perillo-Marcone
CERN, Meyrin, Switzerland

The segmented injection protection absorber (TDIS) foreseen for the High-Luminosity Large Hadron Collider (HL-LHC) project is designed to protect the machine in case of injection kicker malfunctioning. Since the current LHC injection protection absorber has suffered from vacuum issues possibly induced by electron multipacting, numerical studies were done to estimate the electron flux expected on the internal surfaces of the TDIS. This device will consist of three pairs of movable absorbing blocks above and below one beam and a beam screen surrounding the second circulating beam. The build-up of electron cloud in the TDIS was simulated accounting for the presence of two counter-rotating beams, for the configuration of the jaws and for the different materials used for the different surfaces in the device. The simulation studies have also investigated the possibility of coating the most critical surfaces with amorphous carbon in order to mitigate the multipacting.

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reference for this paper ※ https://doi.org/10.18429/JACoW-IPAC2019-WEPTS052

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paper received ※ 13 May 2019 paper accepted ※ 20 May 2019 issue date ※ 21 June 2019

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WEPTS054

Pyg4ometry : A Tool to Create Geometries for Geant4, BDSIM, G4Beamline and FLUKA for Particle Loss and Energy Deposit Studies

interface, detector, shielding, cavity

3244

S.T. Boogert, A. Abramov, J. Albrecht, G. D’Alessandro, L.J. Nevay, W. Shields, S.D. Walker
JAI, Egham, Surrey, United Kingdom

Studying the energy deposits in accelerator components, mechanical supports, services, ancillary equipment and shielding requires a detailed computer readable description of the component geometry. The creation of geometries is a significant bottleneck in producing complete simulation models and reducing the effort required will provide the ability of non-experts to simulate the effects of beam losses on realistic accelerators. The paper describes a flexible and easy to use Python package to create geometries usable by either Geant4 (and so BDSIM or G4Beamline) or FLUKA either from scratch or by conversion from common engineering formats, such as STEP or IGES created by industry standard CAD/CAM packages. The conversion requires an intermediate conversion to STL or similar triangular or tetrahedral tessellation description. A key capability of pyg4ometry is to mix GDML/STEP/STL geometries and visualisation of the resulting geometry and determine if there are any geometric overlaps. An example conversion of a complex geometry used in Geant4/BDSIM is presented.

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reference for this paper ※ https://doi.org/10.18429/JACoW-IPAC2019-WEPTS054

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paper received ※ 19 May 2019 paper accepted ※ 23 May 2019 issue date ※ 21 June 2019

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WEPTS055

Energy Modulation of Electron Beam in Corrugated Dielectric Waveguide

experiment, wakefield, acceleration, electron

3248

A. Lyapin, S.T. Boogert, S.M. Gibson, K. Lekomtsev
JAI, Egham, Surrey, United Kingdom
A. Aryshev, N. Terunuma, J. Urakawa
KEK, Ibaraki, Japan
A.A. Tishchenko
MEPhI, Moscow, Russia
A.A. Tishchenko
NRC, Moscow, Russia

Energy modulated electron beams have a wide range of applications in accelerator physics, for example they can serve as drivers in resonant wakefield acceleration schemes. A strong wakefield induced energy modulation can be produced using a dielectric lined waveguide, the resultant micro-bunched beam is capable of producing coherent terahertz radiation *. We report on observation of energy modulation due to self-wakefields in a few picosecond duration and ~1 nC charge electron bunches of LUCX facility at KEK. To produce the modulation, we used a corrugated dielectric waveguide with an inner radius of 2 mm and a period of corrugation of 10 mm. In this case, the period of corrugation is longer than the wavelength of the main accelerating mode. We show electromagnetic simulations of on-axis electric fields leading to an optimisation of the corrugation period allowing to enhance the accelerating/decelerating fields compared to dielectric lined waveguides with a constant inner radius.
* S. Antipov et al., Experimental observation of energy modulation in electron beams passing though terahertz dielectric wakefield structures, PRL 108, 144801 (2012).

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reference for this paper ※ https://doi.org/10.18429/JACoW-IPAC2019-WEPTS055

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paper received ※ 15 May 2019 paper accepted ※ 23 May 2019 issue date ※ 21 June 2019

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WEPTS057

Recent Studies of the Resonances at a Cell Tune of 0.25 Using the Ibex Paul Trap

resonance, experiment, emittance, space-charge

3255

L. Martin, S.L. Sheehy
JAI, Oxford, United Kingdom
D.J. Kelliher
STFC/RAL/ASTeC, Chilton, Didcot, Oxon, United Kingdom

We use the IBEX linear Paul trap to study the resonance at a cell tune of \frac{1}{4} with both equal and unequal transverse tunes, at a range on intensities. We compare this experimental result to simulation using the PIC code Warp. We find that the experimental result differs from the simulation, which may be explained by the ion loss in the IBEX experiment, which more closely replicates a real accelerator. Knowledge of the tune corresponding to greatest beam loss is important for the design of future high intensity machines.

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reference for this paper ※ https://doi.org/10.18429/JACoW-IPAC2019-WEPTS057

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paper received ※ 30 April 2019 paper accepted ※ 21 May 2019 issue date ※ 21 June 2019

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WEPTS058

BDSIM: Recent Developments and New Features Beyond V1.0

detector, radiation, site, experiment

3259

L.J. Nevay, A. Abramov, J. Albrecht, S.E. Alden, S.T. Boogert, H. Garcia Morales, S.M. Gibson, W. Shields, S.D. Walker
JAI, Egham, Surrey, United Kingdom
J. Snuverink
PSI, Villigen PSI, Switzerland

BDSIM is a program that creates a 3D model of an accelerator from an optical beam line description using a suite of high energy physics software including Geant4, CLHEP and ROOT. In one single simulation the passage of particles can be tracked accurately through an accelerator including the interaction with the accelerator material and subsequent secondary radiation production and transport. BDSIM is regularly used to simulate beam loss and energy deposition as well as machine detector interface studies. In this paper we present the latest developments beyond BDSIM V1.0 added for ongoing studies. For simulation of collimation systems several new additions are described including new element geometry, enhanced sensitivity and output information. The output has been further enhanced with aperture impact information and dose information from scoring meshes. As well as supporting the full suite of Geant4 physics lists, a new user interface is described allowing custom physics lists and user components to be easily included in BDSIM. New undulator, crystal collimator and wire-scanner elements are also described.

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reference for this paper ※ https://doi.org/10.18429/JACoW-IPAC2019-WEPTS058

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paper received ※ 15 May 2019 paper accepted ※ 22 May 2019 issue date ※ 21 June 2019

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WEPTS060

Multi-objective Optimization of 3D Beam Tracking in Electrostatic Beamlines

experiment, quadrupole, lattice, storage-ring

3263

V. Rodin, J.R. Hunt, J. Resta-López, B. Veglia, C.P. Welsch
Cockcroft Institute, Warrington, Cheshire, United Kingdom
J.R. Hunt, J. Resta-López, V. Rodin, B. Veglia, C.P. Welsch
The University of Liverpool, Liverpool, United Kingdom

Funding: *This project has received funding from the European Union’s Horizon 2020 research and innovation programme under the Marie Skłodowska-Curie grant agreement No 721559.
After CERN’s Long Shutdown 2 (LS2) the Extra Low Energy Antiproton (ELENA) ring will begin providing extremely low energy (100 keV) antiproton beams to the antimatter experiments in the AD hall. To allow for simultaneous operation and guarantee maximum efficiency, all transfer lines will be based on electrostatic optics and short pulse (∼100 ns) deflectors. Currently, only a limited number of simulation codes allow a realistic representation of these elements, limiting the capabilities for beam quality optimization. In this contribution methods for modelling realistic electrostatic optical elements and perform 3D tracking studies through these are presented. A combination of finite element methods and experimental measurements are used along with a modified version of the G4Beamline and BMAD codes. Multi-objective optimization techniques are then applied to optimize beam transfer and beam quality at various points along the transfer lines.

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reference for this paper ※ https://doi.org/10.18429/JACoW-IPAC2019-WEPTS060

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paper received ※ 14 May 2019 paper accepted ※ 21 May 2019 issue date ※ 21 June 2019

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WEPTS066

Suppression of Correlated Energy Spread Using Emittance Exchange

cavity, linac, controls, electron

3275

J. Seok, M. Chung
UNIST, Ulsan, Republic of Korea
M.E. Conde, G. Ha, J.G. Power
ANL, Argonne, Illinois, USA

An emittance exchange (EEX) provides a precise longitudinal phase space manipulation of electron bunch. It has been studied for an easy and precise control of temporal distribution, but controls of energy distribution have not been explored. Since the energy control using EEX is under the identical principle to the temporal control, the EEX beamline can control a correlated energy spread of the electron bunch. This would benefit accelerator facilities requiring a low energy spread such as X-ray Free Electron Laser Oscil-lator (XFELO). In this paper, we present principle and preliminary simulation work on the suppression of correlated energy spread using the EEX beamline. ing the EEX beamline.

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reference for this paper ※ https://doi.org/10.18429/JACoW-IPAC2019-WEPTS066

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paper received ※ 21 May 2019 paper accepted ※ 23 May 2019 issue date ※ 21 June 2019

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WEPTS068

A Novel S-Based Symplectic Algorithm for Tracking With Space Charge

space-charge, resonance, optics, proton

3279

J.P. Edelen, D.T. Abell, D.L. Bruhwiler, N.M. Cook, C.C. Hall, S.D. Webb
RadiaSoft LLC, Boulder, Colorado, USA

Funding: This material is based upon work supported by the U.S. Department of Energy, Office of Science, Office of High Energy Physics under Award Number DE-SC0011340
Traditional finite-difference particle-in-cell methods for modeling self-consistent space charge introduce non-Hamiltonian effects that make long-term tracking in storage rings unreliable. Foremost of these is so-called grid heating. Particularly for studies where the Hamiltonian invariants are critical for understanding the beam dynamics, such as nonlinear integrable optics, these spurious effects make interpreting simulation results difficult. To remedy this, we present a novel symplectic spectral space charge algorithm that is free of non-Hamiltonian numerical effects and, therefore, suitable for long-term tracking studies. Results presented here include a detailed study of the solver’s performance under a range of conditions. First, we show benchmarking and convergence studies for different particle shapes and different particle distributions. Then we demonstrate the solver’s ability to preserve Hamiltonian structure by studying the formation of space-charge driven resonances using both our algorithm and traditional PIC.

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reference for this paper ※ https://doi.org/10.18429/JACoW-IPAC2019-WEPTS068

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paper received ※ 14 May 2019 paper accepted ※ 23 May 2019 issue date ※ 21 June 2019

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WEPTS069

The Effects of Stochastic Space Charge in High Brightness Photolectron Beamlines for Ultrafast Electron Diffraction

space-charge, electron, emittance, cathode

3283

M.A. Gordon, Y.K. Kim
University of Chicago, Chicago, Illinois, USA
J.M. Maxson
Cornell University, Ithaca, New York, USA
J.M. Maxson
Cornell University (CLASSE), Cornell Laboratory for Accelerator-Based Sciences and Education, Ithaca, New York, USA

Funding: This work was supported by the U.S. National Science Foundation under award PHY-1549132, the Center for Bright Beams.
As we move to ultra-high brightness photocathodes and ultra-cold beams, we may become more sensitive to stochastic, point-to point effects such as disorder induced heating and the Boersch effect, given the failure of Debye screening. In this study, we explore the effects of stochastic scattering. Modern beam dynamics codes often approximate point to point interactions with a potential created by smoothing the charge over space, removing sensitivity to stochastic effects. This approximation is often used in beamline optimization, because it is much faster. We study the limits of validity of this approximation. In particular, we will simulate effects of stochastic space charge on a high brightness photoemission beamline, an ultrafast electron diffraction beamline with a photocathode temperature of 5 meV with a final beam energy of 225 keV. Emittance dilution in the transverse plane and transverse beam size relative to smooth space charge simulations will be presented.

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reference for this paper ※ https://doi.org/10.18429/JACoW-IPAC2019-WEPTS069

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paper received ※ 13 May 2019 paper accepted ※ 22 May 2019 issue date ※ 21 June 2019

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WEPTS073

Beam-Beam Effect: Crab Dynamics Calculation in JLEIC

luminosity, collider, electron, cavity

3293

H. Huang, F. Lin, V.S. Morozov, Y. Roblin, A.V. Sy, Y. Zhang
JLab, Newport News, Virgina, USA
I. Neththikumara, S. Sosa, B. Terzić
ODU, Norfolk, Virginia, USA

The electron and ion beams of a future Electron Ion Collider (EIC) must collide at an angle for detection, machine and engineering design reasons. To avoid associated luminosity reduction, a local crabbing scheme is used where each beam is crabbed before collision and de-crabbed after collision. The crab crossing scheme then provides a head-on collision for beams with a non-zero crossing angle. We develop a framework for accurate simulation of crabbing dynamics with beam-beam effects by combining symplectic particle tracking codes with a beam-beam model based on the Bassetti-Erskine analytic solution. We present simulation results using our implementation of such a framework where the beam dynamics around the ring is tracked using Elegant and the beam-beam kick is modeled in Python.

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reference for this paper ※ https://doi.org/10.18429/JACoW-IPAC2019-WEPTS073

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paper received ※ 16 May 2019 paper accepted ※ 22 May 2019 issue date ※ 21 June 2019

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WEPTS075

Effect of Beam-Beam Kick on Electron Beam Quality in First Bunched Electron Cooler

electron, solenoid, alignment, focusing

3297

S. Seletskiy, M. Blaskiewicz, A.V. Fedotov, D. Kayran, J. Kewisch
BNL, Upton, Long Island, New York, USA

The low energy RHIC electron cooler (LEReC) currently under commissioning at BNL is going to be the first non-magnetized bunched electron cooler (EC). For successful cooling LEReC requires that the electrons in the cooling section (CS) have small angles with respect to co-propagating ions. Since there is no strong magnetic field in the CS, the effects of ions on both the trajectory and focusing of the e-bunches is critical. In this paper we consider the ion beam kick on the electron bunches and derive requirements to the respective alignment of electron and ion beams in non-magnetized coolers.

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reference for this paper ※ https://doi.org/10.18429/JACoW-IPAC2019-WEPTS075

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paper received ※ 08 April 2019 paper accepted ※ 22 May 2019 issue date ※ 21 June 2019

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WEPTS078

Chaos Indicators for Studying Dynamic Aperture in the IOTA Ring with Protons

space-charge, dynamic-aperture, lattice, betatron

3301

K. Hwang, C.E. Mitchell, R.D. Ryne
LBNL, Berkeley, California, USA

The Integrable Optics Test Accelerator (IOTA) is a novel storage ring under commissioning at Fermi National Accelerator Laboratory designed (in part) to investigate the dynamics of beams in the presence of highly nonlinear transverse focusing fields that generate integrable single-particle motion. In this study, we explore the sensitivity of the lattice dynamic aperture to the presence of nonlinear space charge. For this purpose, two distinct chaos indicators are compared (frequency map analysis and forward-backward integration). Because the integrability of motion requires integer betatron tune advance between passes through the nonlinear magnetic element, a large role is played by space-charge-induced tune spread. As a result, these tools are also applied to a toy model of the IOTA lattice to investigate the sensitivity of dynamic aperture to violations of the integer tune advance condition.

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reference for this paper ※ https://doi.org/10.18429/JACoW-IPAC2019-WEPTS078

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paper received ※ 14 May 2019 paper accepted ※ 22 May 2019 issue date ※ 21 June 2019

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WEPTS079

Analysis of Particle Noise in a Gridless Spectral Poisson Solver for Symplectic Multiparticle Tracking

space-charge, focusing, emittance, plasma

3304

C.E. Mitchell, J. Qiang
LBNL, Berkeley, California, USA

Funding: This work was was supported by the Director, Office of Science, Office of High Energy Physics, of the U.S. Department of Energy under Contract No. DE-AC02-05CH11231.
Gridless symplectic methods for self-consistent modeling of space charge in intense beams possess several advantages over traditional momentum-conserving particle-in-cell methods, including the absence of numerical grid heating and the presence of an underlying multi-particle Hamiltonian. Despite these advantages, there remains evidence of irreversible emittance growth due to numerical particle noise. For a class of such algorithms, a first-principles kinetic model of the numerical particle noise is obtained and applied to gain insight into noise-induced entropy growth and thermal relaxation.

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reference for this paper ※ https://doi.org/10.18429/JACoW-IPAC2019-WEPTS079

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paper received ※ 14 May 2019 paper accepted ※ 22 May 2019 issue date ※ 21 June 2019

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WEPTS083

Multipass Simulations of Space Charge Compensation using Electron Columns at IOTA

space-charge, electron, cavity, proton

3313

C.S. Park, E.G. Stern
Fermilab, Batavia, Illinois, USA
S. Chattopadhyay, B.T. Freemire
Northern Illinois University, DeKalb, Illinois, USA
C.E. Mitchell, R.D. Ryne
LBNL, Berkeley, California, USA

Defocusing repulsive forces due to self space charge fields lead to degradation of high-intensity particle beams. Being of particular concern for low- and medium-energy proton beams, they result in emittance growth, beam halo formation, and beam loss. They set stringent limits on the intensity of frontier accelerators; therefore, the mitigation of space charge effects is a crucial challenge to improve proton beam intensity. The space charge effects in a positively charged proton beam can be effectively compensated using negatively charged electron columns. In this paper, we present the results of simulations using Synergia of the Electron Column lattice for IOTA. Beam loss due to space charge effects and aperture restrictions have been studied, as well as bunch formation and matching using an adiabatic ramp of the RF cavity. The results show the need for space charge compensation, and provide the basis for integration of the Synergia and Warp codes in order to form a complete simulation of space charge compensation using an Electron Column in IOTA.

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reference for this paper ※ https://doi.org/10.18429/JACoW-IPAC2019-WEPTS083

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paper received ※ 16 May 2019 paper accepted ※ 22 May 2019 issue date ※ 21 June 2019

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WEPTS088

Integration of Cavity Design and Beam Dynamics Simulation Using the Parallel IMPACT and the ACE3P Codes

cavity, emittance, electron, gun

3317

J. Qiang, D.A. Bizzozero
LBNL, Berkeley, California, USA
L. Ge, Z. Li, C.-K. Ng, L. Xiao
SLAC, Menlo Park, California, USA

Funding: This work was supported by the U.S. Department of Energy under Contract No. DE-AC02-05CH11231 and DE-AC02-76SF00515,
The 3D parallel code suite IMPACT has been extensively used in the beam dynamics study of photoinjectors while the 3D parallel code ACE3P has been extensively used in the RF cavity design. In this paper, we propose integrating the ACE3P cavity design and the IMPACT beam dynamics simulation into a single work flow. Such a workflow enables efficient simulation of 3D effects(e.g. RF coupler) on high performance computers.

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reference for this paper ※ https://doi.org/10.18429/JACoW-IPAC2019-WEPTS088

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paper received ※ 07 May 2019 paper accepted ※ 22 May 2019 issue date ※ 21 June 2019

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WEPTS090

Suppression of Microbunching Instability Through Dispersive Lattice

bunching, electron, linac, quadrupole

3325

J. Qiang, B. Li
LBNL, Berkeley, California, USA

Funding: This work was supported by the U.S. Department of Energy under Contract No. DE-AC02-05CH11231 and used computer resources at the National Energy Research Scientific Computing Center.
The microbunching instability from the initial small modulation such as shot-noise can be amplified by longitudinal space-charge force and causes significant electron beam quality degradation at the exit of accelerator for the next generation x-ray free electron laser. In the paper, we present analytical and numerical simulation studies of a novel method using dispersion leakage from some quadrupoles inside a chicane.

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reference for this paper ※ https://doi.org/10.18429/JACoW-IPAC2019-WEPTS090

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paper received ※ 26 April 2019 paper accepted ※ 23 May 2019 issue date ※ 21 June 2019

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WEPTS092

3d Start-to-End Simulations of the Coherent Electron Cooling

electron, FEL, plasma, kicker

3329

J. Ma, V. Litvinenko, G. Wang
BNL, Upton, Long Island, New York, USA
V. Litvinenko
Stony Brook University, Stony Brook, USA

Coherent electron cooling (CeC) is a novel technique for rapidly cooling high-energy, high-intensity hadron beam. Two designs of coherent electron cooler, with a free electron laser (FEL) amplifier and a plasma-cascade micro-bunching amplifier, are cost effective and don’t require separation of hadrons and electrons. These schemes are used for the demonstration experiment in the Relativistic Heavy Ion Collider (RHIC) at Brookhaven National Laboratory (BNL). SPACE, a parallel, relativistic 3D electromagnetic Particle-in-Cell (PIC) code, has been used for simulation studies of these two coherent electron cooler systems.

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reference for this paper ※ https://doi.org/10.18429/JACoW-IPAC2019-WEPTS092

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paper received ※ 15 April 2019 paper accepted ※ 22 May 2019 issue date ※ 21 June 2019

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WEPTS100

The ESR Closed Orbit Calculation and Simulation

controls, electron, experiment, MMI

3349

S. Dastan, S. Dastan, R. Saffari
University of Guilan, Rasht, Iran
S. Dastan, J. Rahighi
ILSF, Tehran, Iran
S. Livinov, M. Steck
GSI, Darmstadt, Germany

The commissioning of the ESR with a new control system based on the LSA (LHC System Architecture) has started recently. This new control system is under development and considers all aspects of the expected functionality to operate the GSI/FAIR accelerators and incorporates the present GSI controls infrastructure*. Two years ago, the old control system which was based on outdated computers and operating system, was discontinued. So, both the heavy ion synchrotron SIS-18 and the Experimental Storage Ring (ESR) operation from now on have to be performed with the new FAIR control system. In order to introduce an improved model to the control system change, new calculations and simulations for SIS and ESR are necessary. In this paper we summarize the results of closed orbit calculations for the ESR which are done with three different codes, namely: ELEGANT*, MAD-X and MIRKO. Also, because the results of ELEGANT and MAD-X in this issue are similar to each other, we present ELEGANT results in the report.
* R. Bär, DEVELOPMENT OF A NEW CONTROL SYSTEM FOR THE FAIR ACCELERATOR COMPLEX AT GSI. Kobe.
** Borland, M., elegant: A Flexible SDDS-Compliant Code for Accelerator Simulation.

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reference for this paper ※ https://doi.org/10.18429/JACoW-IPAC2019-WEPTS100

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paper received ※ 29 April 2019 paper accepted ※ 22 May 2019 issue date ※ 21 June 2019

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WEPTS101

A General Comparison on Impedance Theory and CST Simulation of Discontinuities

impedance, vacuum, coupling, storage-ring

3352

N. Khosravi, E. Ahmadi, M. Akhyani, S. Dastan, A.M. Mash’al
ILSF, Tehran, Iran
H. Karimi
Isfahan University of Technology, Isfahan, Iran

Inhomogeneity of vacuum chamber components is the main source of coupling impedance. Nowadays, wake potential is mostly predictable by 3D codes. Analytical prediction of impedance theories can be helpful as a side solution. On the other hand, some asymmetries in the geometry of components might make troubles and lead to imprecise numerical results in 3D simulations. Analytical approximation of discontinuities, holes, and grooves can give us an estimation of expected results and can be used as a benchmark in the case that we do not have any experimental data. To clarify the validity of theoretical expressions, general discontinuities are simulated in CST. The comparison of final results is presented here. At last, resistive wall impedance and some general discontinuities of components at ILSF storage ring are compared from the theoretical and simulation point of view.

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reference for this paper ※ https://doi.org/10.18429/JACoW-IPAC2019-WEPTS101

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paper received ※ 01 May 2019 paper accepted ※ 24 May 2019 issue date ※ 21 June 2019

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WEPTS105

Simulation of Sirius Booster Commissioning

MMI, injection, booster, closed-orbit

3366

M.B. Alves, L. Liu, F.H. de Sá
LNLS, Campinas, Brazil

Sirius is the new 3 GeV fourth-generation low emittance light source under construction at the Brazilian Synchrotron Light Laboratory. In order to study strategies forthe commissioning, different scenarios were studied by tracking simulations on lattice models with realistic alignment and magnet excitation errors, taking into account the finite precision of the beam diagnostic devices. We developed a commissioning algorithm that provides an efficient adjustment of the on-axis injection parameters, trajectory and closed orbit corrections and tuning of the RF parameters. With this algorithm it was possible to obtain a stable beam for thousands of turns in all the random machines simulated. The algorithms allows for partially automated commissioning procedures.

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reference for this paper ※ https://doi.org/10.18429/JACoW-IPAC2019-WEPTS105

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paper received ※ 15 May 2019 paper accepted ※ 22 May 2019 issue date ※ 21 June 2019

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WEPTS108

Emittance Exchange in MICE

emittance, experiment, collider, factory

3378

C. Brown
STFC/RAL/ISIS, Chilton, Didcot, Oxon, United Kingdom
C.G. Whyte
USTRAT/SUPA, Glasgow, United Kingdom

Funding: STFC, NSF, DOE, INFN, CHIPP and more
The Muon Ionization Cooling Experiment, MICE, has demonstrated transverse emittance reduction through ionization cooling. Transverse ionization cooling can be used either to prepare a beam for acceleration in a neutrino factory or for the initial stages of beam cooling in a muon collider. Later stages of ionization cooling in the muon collider require the longitudinal emittance to be manipulated using emittance exchange and reverse emittance exchange, where emittance is exchanged from and to longitudinal phase space respectively. A wedge absorber within the MICE cooling channel has been used to experimentally demonstrate reverse emittance exchange in ionization cooling. Parameters for this test have been explored in simulation and applied to experimental configurations using a wedge absorber when collecting data in the MICE beam. This analysis of reverse emittance exchange is presented in detail.

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reference for this paper ※ https://doi.org/10.18429/JACoW-IPAC2019-WEPTS108

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paper received ※ 14 May 2019 paper accepted ※ 21 May 2019 issue date ※ 21 June 2019

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THPMP014

2D TRACKING CODE FOR DRIFT TUBE LINAC

DTL, linac, focusing, drift-tube-linac

3482

A. Yamaguchi, K. Nakayama, K. Okaya, K. Sato
Toshiba, Yokohama, Japan
N. Hayashizaki
RLNR, Tokyo, Japan
Y. Iwata, S. Yamada
NIRS, Chiba-shi, Japan
T. Takeuchi
Toshiba Energy Systems & Solutions Corporation, Keihin Product Operations, Yokohama, Japan

A 2D tracking code has been developed for Alternating-Phase-Focusing drift tube linacs (APF-DTL). This code can design DTLs with a 2D electric field simulation and particle tracking by approximate equations. In this paper, we describe an outline of the 2D tracking code and a comparison of 2D tracking results and 3D simulation.

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reference for this paper ※ https://doi.org/10.18429/JACoW-IPAC2019-THPMP014

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paper received ※ 15 May 2019 paper accepted ※ 22 May 2019 issue date ※ 21 June 2019

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THPMP020

Single-Shot Cascade High Energy Electron Radiography based on Strong Permanent Magnet Quadrupole Composed Imaging Lens

electron, experiment, quadrupole, optics

3491

Z. Zhou, Y.-C. Du, W.-H. Huang
TUB, Beijing, People’s Republic of China

High energy electron imaging, an extension of conventional transmission electron microscopy, is suitable for imaging of thicker objects and expected to be a promising tool for diagnostics of high energy density physics (HEDP). A cascade high energy electron imaging system using two-stage imaging lenses based on strong permanent magnet quadrupoles is designed, optimized and finally installed at Tsinghua university. Encouraging result of 1.6-μm space resolution is obtained in our primary experiments, along with the clear imaging of a spherical capsule as a substitute of the targets used in inertial confinement fusion. Successful implement of cascade high energy electron imaging system is necessary for reaching better resolving power of the imaging system, and well matching of design, simulation with experimental results paves the way to high energy electron microscopy to provide full capacities for diagnostics of HEDP with sub-um and picosecond spatiotemporal resolutions.

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reference for this paper ※ https://doi.org/10.18429/JACoW-IPAC2019-THPMP020

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paper received ※ 07 May 2019 paper accepted ※ 21 May 2019 issue date ※ 21 June 2019

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THPMP021

X-ray Dose Rate of 6/4 MeV European S-band Linac Structure for Industrial Application at RTX

target, electron, linac, operation

3494

P. Buaphad, I.G. Jeong, Y. Joo, H.R. Lee
University of Science and Technology of Korea (UST), Daejeon, Republic of Korea
I.G. Jeong, J.Y. Lee
Korea Atomic Energy Research Institute (KAERI), Daejeon, Republic of Korea
Y. Joo, Y. Kim, H.R. Lee
KAERI, Daejon, Republic of Korea
H.D. Park, S. Song
RTX, Daejeon, Republic of Korea

Recently, RTX has been developing a 6/4 MeV European S-band (= 2998 MHz) industrial linac by using a magnetron with a low RF power of about 3 MW for container inspection system (CIS). Its accelerating structure is designed to operate in π/2 mode by coupling 6 accelerating cells together through 5 side-coupled cells. In CIS, high dose rate X-rays from MeV-energy electron beam has been used to detect the possible presence of contrabands in cargoes or truck containers. To determine a dose rate output, the X-ray dose rate can be simulated by using FLUKA Monte Carlo simulation. The aim of this work was to study the effects of thickness of X-ray target on dose rate as well as X-ray dose map at 1.0 m away from the X-ray target. This study gives the thickness of target in which the dose rate can be highest and electron beam current can be lowest.

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reference for this paper ※ https://doi.org/10.18429/JACoW-IPAC2019-THPMP021

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paper received ※ 24 May 2019 paper accepted ※ 24 May 2019 issue date ※ 21 June 2019

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THPMP033

Beam Characterisation Using MEDIPIX3 and EBT3 Film at the Clatterbridge Proton Therapy Beamline

proton, detector, radiation, experiment

3510

J.S.L. Yap, J. Resta-López, R. Schnuerer, C.P. Welsch
Cockcroft Institute, Warrington, Cheshire, United Kingdom
N.J.S. Bal
ASI, Amsterdam, The Netherlands
N.J.S. Bal, M. Fransen, F. Linde
NIKHEF, Amsterdam, The Netherlands
A. Kacperek
The Douglas Cyclotron, The Clatterbridge Cancer Centre NHS Foundation Trust, Wirral, United Kingdom
J.L. Parsons
Cancer Research Centre, University of Liverpool, Liverpool, United Kingdom
J. Resta-López, R. Schnuerer, C.P. Welsch
The University of Liverpool, Liverpool, United Kingdom

Funding: EU FP7 grant agreement 215080, H₂020 Marie Skłodowska-Curie grant agreement No 675265 - Optimization of Medical Accelerators (OMA) project and the Cockcroft Institute core grant STGA00076-01.
The Clatterbridge Cancer Centre (CCC) in the UK is a particle therapy facility providing treatment for ocular cancers using a 60 MeV passively scattered proton therapy beam. A model of the beamline using the Monte Carlo Simulation toolkit Geant4 has been developed for accurate characterisation of the beam. In order to validate the simulation, a study of the beam profiles along the delivery system is necessary. Beam profile measurements have been performed at multiple positions in the CCC beam line using both EBT3 GAFchromic film and Medipix3, a single quantum counting chip developed specifically for medical applications, typically used for x-ray detection. This is the first time its performance has been tested within a clinical, high proton flux environment. EBT3 is the current standard for conventional radiotherapy film dosimetry and was used to determine the dose and for correlation to fluence measured by Medipix3. The count rate linearity and doses recorded with Medipix3 were evaluated across the full range of available beam intensities, up to 3.12 x 10¹⁰ protons/s. The applicability of Medipix3 for proton therapy dosimetry is discussed and compared against the performance of EBT3.

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reference for this paper ※ https://doi.org/10.18429/JACoW-IPAC2019-THPMP033

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paper received ※ 14 May 2019 paper accepted ※ 22 May 2019 issue date ※ 21 June 2019

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THPMP034

Simulating Matter Interactions of Partially Stripped Ions in BDSIM

electron, target, hadron, dipole

3514

A. Abramov, S.T. Boogert, L.J. Nevay
JAI, Egham, Surrey, United Kingdom

Acceleration and storage of beams of relativistic partially stripped ions is more challenging than in the case of fully stripped ions because the interactions with matter, such as those with residual gas and collimators can strip electrons via ionisation. BDSIM is a code for the simulation of energy deposition and charged particle backgrounds in accelerators that uses the Geant4 physics library. Geant4 includes a broad range of ion elastic and inelastic interactions and allows the definition of partially stripped ion beams. However, no models are currently available to handle in-flight interactions involving the bound electrons. In this paper we present a semi-empirical model of beam ion stripping by material atoms that is implemented in BDSIM as an extension of Geant4’s existing physics processes and is fully integrated into a comprehensive set of matter interactions for partially stripped ions. The stripping cross-section for select cases and results from comprehensive simulations are presented.

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reference for this paper ※ https://doi.org/10.18429/JACoW-IPAC2019-THPMP034

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paper received ※ 15 May 2019 paper accepted ※ 23 May 2019 issue date ※ 21 June 2019

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THPMP042

Performance Optimization of Ion Beam Therapy

proton, FEL, diagnostics, medical-accelerators

3537

C.P. Welsch
Cockcroft Institute, Warrington, Cheshire, United Kingdom
C.P. Welsch
The University of Liverpool, Liverpool, United Kingdom

Funding: This project has received funding from the European Union’s Horizon 2020 research and innovation programme under the Marie SkłodowskaCurie grant agreement No 675265.
Proton beam therapy promises significant advantages over other forms of radiation therapy. However, to assure the best possible cancer care for patients further R&D into novel beam imaging and patient diagnostics, enhanced biological and physical models in Monte Carlo codes, as well as clinical facility design and optimization is required. Within the pan-European Optimization of Medical Accelerators (OMA) project collaborative research is being carried out between universities, research and clinical facilities, and industry in all of these areas. This contribution presents results from studies into low-intensity proton beam diagnostics, prompt gamma-based range verification in proton therapy, as well as prospects for a new proton irradiation facility for radiobiological measurements at an 18 MeV cyclotron within OMA. These results are then connected to the wider project aims of enhancing ion beam therapy. A summary of past and future events organised by the OMA consortium is also given.

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reference for this paper ※ https://doi.org/10.18429/JACoW-IPAC2019-THPMP042

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paper received ※ 10 May 2019 paper accepted ※ 23 May 2019 issue date ※ 21 June 2019

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THPMP046

Knowledge Exchange Within the Particle Accelerator Community via Cloud Computing

GUI, software, HOM, electron

3548

D.L. Bruhwiler, D.T. Abell, N.M. Cook, C.C. Hall, M.V. Keilman, P. Moeller, R. Nagler, B. Nash
RadiaSoft LLC, Boulder, Colorado, USA

Funding: Work supported by US Department of Energy under Award Nos. DE-SC0011237, DE-SC0011340, DE-SC0018719, DE-SC0015212, DE-SC0017181 and DE-SC0017162.
The development, testing and use of particle accelerator modeling codes is a core competency of accelerator research laboratories around the world, and likewise for synchrotron radiation and X-ray optics codes at lightsource facilities. Such codes require time and training to learn a command-line workflow involving multiple input and configuration files, execution on a high-performance server or cluster, post-processing with specialized software and finally visualization. Such workflows are error prone an difficult to reproduce. Cloud computing and UI design are core competencies of RadiaSoft LLC, where the Sirepo* framework is being developed to make state of the art codes available in the browser of any desktop, laptop or tablet. We present our initial successes as real world examples of knowledge exchange (KE) between industry and the research community. This work is leading to broader knowledge exchange throughout the community by facilitating education of students and enabling instantaneous sharing of simulation details between colleagues. Sirepo design objectives include: seamless integration with legacy codes, low barrier to entry for new users, configuration transfer to command line mode, catalog of provenance to aid reproducibility, and simplified collaboration through multimodal sharing. The Sirepo Scientific Gateway** allows users to directly test the software. The combination of intuitive browser-based GUIs and Sirepo’s server-side application container technology enables simplified computational archiving and reproducibility. If embraced by the community, this could become an important asset for the design, commissioning and future upgrade of particle accelerator and X-ray beamline facilities.
* Sirepo cloud computing framework, https://github.com/radiasoft/sirepo
** Sirepo Scientific Gateway, https://sirepo.com

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reference for this paper ※ https://doi.org/10.18429/JACoW-IPAC2019-THPMP046

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paper received ※ 21 May 2019 paper accepted ※ 23 May 2019 issue date ※ 21 June 2019

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THPMP047

Advanced Modeling and Optimization of Thermionic Energy Converters

interface, cathode, framework, diagnostics

3552

J.P. Edelen, N.M. Cook, C.C. Hall, Y. Hu
RadiaSoft LLC, Boulder, Colorado, USA
J.-L. Vay
LBNL, Berkeley, California, USA

Funding: This material is based upon work supported by the U.S. Department of Energy, Office of Science, Office of High Energy Physics under Award Number DE-SC0017162
Thermionic energy converters (TEC) are a class of thermoelectric devices, which promise improvements to the efficiency and cost of both small- and large-scale electricity generation. A TEC is comprised of a narrowly-separated thermionic emitter and an anode. Simple structures are often space-charge limited as operating temperatures produce currents exceeding the Child-Langmuir limit. We present results from 3D simulations of these devices using the particle-in-cell code Warp, developed at Lawrence Berkeley National Lab. We demonstrate improvements to the Warp code permitting high fidelity simulations of complex device geometries. These improvements include modeling of non-conformal geometries using mesh refinement and cut-cells with a dielectric solver, in addition to importing geometries directly from standard CAD output. In this paper we showcase some of these new features and demonstrate their use.

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reference for this paper ※ https://doi.org/10.18429/JACoW-IPAC2019-THPMP047

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paper received ※ 14 May 2019 paper accepted ※ 22 May 2019 issue date ※ 21 June 2019

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THPMP050

Progress on the Optics Modeling of BMI’s Ion Rapid-Cycling Medical Synchrotron at BNL

dipole, optics, focusing, GUI

3561

F. Méot, P.N. Joshi, N. Tsoupas
BNL, Upton, Long Island, New York, USA
J.P. Lidestri
Best Medical International, Springfield, USA

Funding: A project funded by Best Medical International, in the framework of a Technical Services Agreement (No. TSA-NF-18-50) with Brookhaven National Laboratory.
The Brookhaven National Laboratory continues to provide technical support and guidance to Best Medical International to build and test a 60 degree magnetic arc of a rapid-cycling ion synchrotron for cancer treatment. The 60 degree magnetic sector on its guirder has undergone field measurements, including the production of partial 3D field maps. Concurrently, OPERA field map computations as well as lattice and beam dynamics simulations have been performed, aimed at both preparing and analyzing the field measurements. Contingency responses aimed at adapting to non-ideal orbit and optics have been devised. These works and their outcomes are summarized here.

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reference for this paper ※ https://doi.org/10.18429/JACoW-IPAC2019-THPMP050

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paper received ※ 14 May 2019 paper accepted ※ 22 May 2019 issue date ※ 21 June 2019

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THPGW002

A Passive Plasma Beam Dump Study with Application to EuPRAXIA

plasma, wakefield, electron, laser

3581

R.P. Nunes
UFRGS, Porto Alegre, Brazil
A. Bonatto
University of Manchester, Manchester, United Kingdom
G.X. Xia
UMAN, Manchester, United Kingdom

Funding: The author R. P. Nunes acknowledges the financial support provided by FAPERGS.
This work presents a study about a passive dumping scheme applied to the beam generated by the accelerator stage of the EuPraxia experiment. Particle-in-cell simulations have been carried out and its results are compared with analytical estimates, showing a reasonable agreement.

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reference for this paper ※ https://doi.org/10.18429/JACoW-IPAC2019-THPGW002

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paper received ※ 05 May 2019 paper accepted ※ 22 May 2019 issue date ※ 21 June 2019

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THPGW003

Energy Loss of an Electron Beam with Gaussian Density Profile Propagating in a Passive Plasma Beam Dump

plasma, wakefield, electron, laser

3584

A. Bonatto
University of Manchester, Manchester, United Kingdom
R.P. Nunes
UFRGS, Porto Alegre, Brazil
G.X. Xia
UMAN, Manchester, United Kingdom

Funding: CNPq, and FAPERGS, from Brazil.
A semi-analytical 1D model is derived for the total energy loss of an electron beam with Gaussian density profile undergoing a passive plasma beam dump. The model is compared to a previous one, obtained for a half-sine longitudinal density profile. It is shown that both models agree if the beam density profiles are properly matched, and if their sizes are small in comparison to the length of wakefield decelerating length. The beam energy obtained from both models is compared to 1D PIC simulation results.

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reference for this paper ※ https://doi.org/10.18429/JACoW-IPAC2019-THPGW003

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paper received ※ 09 May 2019 paper accepted ※ 23 May 2019 issue date ※ 21 June 2019

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THPGW004

The Use of an RF Undulator in the Design of an Accelerating Structure

proton, acceleration, focusing, undulator

3587

N.V. Avreline
TRIUMF, Vancouver, Canada
P.G. Alexey, S.M. Polozov
MEPhI, Moscow, Russia

The idea of accelerating a beam in the accelerating structures based on an RF undulator poses great advantages in high current proton and ions accelerators. The accelerating structure based on an RF undulator uses a combinational wave that consists of the zeroth and the first harmonics for acceleration and focusing. This paper presents the development of this accelerating structure for acceleration of a beam. In particular, we show that this structure is an H-type resonator composed from five coupled sections.

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reference for this paper ※ https://doi.org/10.18429/JACoW-IPAC2019-THPGW004

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paper received ※ 01 May 2019 paper accepted ※ 21 May 2019 issue date ※ 21 June 2019

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THPGW005

Recent Developments of the 520 MeV Cyclotron’s High-Power RF System at TRIUMF

cyclotron, operation, rf-amplifier, coupling

3591

N.V. Avreline, Y. Bylinskii, D. Gregoire, B. Jakovljevic, R.E. Laxdal, X. Wang, B.S. Waraich, V. Zvyagintsev
TRIUMF, Vancouver, Canada

520 MeV Cyclotron’s High-Power RF System has been in the state of continuous operation for over 50 years since its commissioning. This paper describes the recent upgrades of the RF System, the main goal of which was to improve reliability. Specially, we discuss the upgrades done to the RF Transmission Line (TL), the RF Power Amplifier (PA) components and their diagnostics tools. We upgraded the structure of Intermediate Power Amplifier (IPA), installed Solid State (SS) driver and are in the process of replacing tubes with a SS option for IPA and PA.

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reference for this paper ※ https://doi.org/10.18429/JACoW-IPAC2019-THPGW005

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paper received ※ 08 May 2019 paper accepted ※ 20 May 2019 issue date ※ 21 June 2019

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THPGW012

Wake-T: A Fast Particle Tracking Code for Plasma-Based Accelerators

plasma, emittance, electron, laser

3601

A. Ferran Pousa, R.W. Aßmann, A. Martinez de la Ossa
DESY, Hamburg, Germany
A. Ferran Pousa
University of Hamburg, Institut für Experimentalphysik, Hamburg, Germany

The design and study of plasma-based accelerators relies typically on costly 3D Particle-In-Cell (PIC) simulations due to the complexity of the laser-plasma and beam-plasma interactions. However, under certain assumptions, more efficient and simple models can be implemented to describe the dynamics of the accelerated beams. Wake-T (Wakefield particle Tracker) is a new code for analytical and numerical particle tracking in plasma-based accelerators which is orders of magnitude faster than conventional PIC codes. This allows for fast parameter scans and is well suited for the initial design and optimization of these novel accelerators.

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reference for this paper ※ https://doi.org/10.18429/JACoW-IPAC2019-THPGW012

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paper received ※ 24 April 2019 paper accepted ※ 21 May 2019 issue date ※ 21 June 2019

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THPGW014

Tolerance Studies and Limitations for Photonic Bandgap Fiber Accelerators

laser, acceleration, photon, electron

3605

L. Genovese, R.W. Aßmann, U. Dorda, M. Kellermeier, W. Kuropka, F. Lemery, F. Mayet
DESY, Hamburg, Germany
W. Kuropka, F. Mayet
University of Hamburg, Institut für Experimentalphysik, Hamburg, Germany

Laser-driven hollow core photonic bandgap (PBG) fibers were proposed by Lin in 2001 as high-gradient accelerators. The central defect in the transversely periodic lattice supports an accelerating mode for synchronous acceleration in the ultra-relativistic regime. The optical frequencies in such dielectric laser accelerators motivate a sensitivity and tolerance study to overcome manufacturing imperfections. Finally we discuss the propagation characteristics of Lin-fibers and find that small-bandwidth (~ns) pulses would be needed for efficient acceleration over longer distances.

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reference for this paper ※ https://doi.org/10.18429/JACoW-IPAC2019-THPGW014

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paper received ※ 16 May 2019 paper accepted ※ 22 May 2019 issue date ※ 21 June 2019

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THPGW017

Self-Modulation Instability of Electron Beams in Plasma Channels of Variable Length

plasma, wakefield, laser, electron

3616

O. Lishilin, Y. Chen, J.D. Good, M. Groß, I.I. Isaev, C. Koschitzki, M. Krasilnikov, G. Loisch, A. Oppelt, H.J. Qian, F. Stephan
DESY Zeuthen, Zeuthen, Germany
R. Brinkmann, A. Martinez de la Ossa, J. Osterhoff
DESY, Hamburg, Germany
F.J. Grüner
Center for Free-Electron Laser Science, Universität Hamburg, Hamburg, Germany
T.J. Mehrling, C.B. Schroeder
LBNL, Berkeley, USA

The self-modulation instability (SMI) of long (in respect to the plasma wavelength) charged particle beams passing through plasma enables the use of currently existing high energy charged particle beams as drivers for plasma wakefield accelerators. At the Photo Injector Test facility at DESY in Zeuthen (PITZ) the SMI of electron beams is studied *, **. An enhanced experimental setup includes a plasma channel of variable length which allows to investigate in details the development stages of the SMI by measuring the instability growth rate and phase velocity as a function of propagation distance in the plasma. In this contribution we present the experimental setup improvements, first measurement results and supporting beam dynamics simulations.
* M. Gross, et al., Phys. Rev. Lett., vol. 120, p. 144802, 2018.
** G. Loisch, et al., Plasma Physics and Controlled Fusion, vol. 61(4), p. 045012, 2019

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reference for this paper ※ https://doi.org/10.18429/JACoW-IPAC2019-THPGW017

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paper received ※ 11 May 2019 paper accepted ※ 23 May 2019 issue date ※ 21 June 2019

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THPGW039

Moderation of Positive Muons by Helium Gas

proton, experiment, scattering, vacuum

3667

Y. Li, Y. Bao, R. Fan, X. Li, X. Tong
IHEP, Beijing, People’s Republic of China
C.J. Ning, P.C. Wang
IHEP CSNS, Guangdong Province, People’s Republic of China

Funding: This work is supported by CAS, National Natural Science Foundation of China (Grant No. 11875281), and China Postdoctoral Science Foundation (Grant No. 2019M650845)
Efficiently creating beams of spin-polarized positive muons with energies between eV and keV (so-called slow muon beams) is important for further development and application of muon spin rotation, relaxation, and resonance techniques. One existing moderation method involves the use of wide-band-gap materials as moderators such as rare gas solids and solid nitrogen thin films (band-gap energy between 11 eV and 22 eV). Based on this moderation method, we have studied the use of helium gas as a moderator, with the goal of producing the slow muon beam more efficiently. Because of helium’s high (24.6 eV) ionization energy and because the cross section for muonium formation is suppressed in helium gas, we expect the production of slow muons using helium gas to be highly efficient.

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reference for this paper ※ https://doi.org/10.18429/JACoW-IPAC2019-THPGW039

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paper received ※ 01 May 2019 paper accepted ※ 23 May 2019 issue date ※ 21 June 2019

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THPGW040

Decay Muon Beamline Design for EMuS

target, proton, solenoid, dipole

3670

Y.P. Song, Y. Bao, C. Meng, J.Y. Tang
IHEP, Beijing, People’s Republic of China
Y.K. Chen, H.T. Jing
IHEP CSNS, Guangdong Province, People’s Republic of China

Funding: This work is supported by the Chinese Academy of Sciences.
The beamline design philosophies and simulation re-sults of the decay muon on Experimental Muon Source (EMuS) are reported in this paper. The beamline is com-posed of solenoids to keep large acceptance, and has been optimized for 45, 150 and 450 MeV/c decay muon re-spectively according to the π spectra optimization results from target station. Decay muons from 45 to 150 MeV/c are designed for μSR applications, and 150 to 450 MeV/c are designed for muon imaging, which is unique on the high momentum perspective. Negative muons from 45 to 150 MeV/c are designed for muonic applications. The momentum range of decay muon is tuneable between 45 and 450 MeV/c.

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reference for this paper ※ https://doi.org/10.18429/JACoW-IPAC2019-THPGW040

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paper received ※ 01 May 2019 paper accepted ※ 23 May 2019 issue date ※ 21 June 2019

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THPGW064

Commissioning Results of the Tertiary Beam Lines for the CERN Neutrino Platform Project

MMI, target, experiment, positron

3738

M.S. Rosenthal, N. Charitonidis, E.M. Nowak, I. Ortega Ruiz
CERN, Geneva, Switzerland
A.C. Booth
University of Sussex, Brighton, United Kingdom
Y. Chatzidaki
National Technical University of Athens, Zografou, Greece
Y. Karyotakis
IN2P3-LAPP, Annecy-le-Vieux, France
P.R. Sala
INFN-Milano, Milano, Italy

For many decades the CERN North Area facility at the Super Proton Synchrotron (SPS) has delivered secondary beams to various fixed target experiments and test beams. In 2018, two new tertiary extensions of the existing beam lines, designated "H2-VLE" and "H4-VLE", have been constructed and successfully commissioned. These beam lines have been designed to provide charged particles of both polarities in the momentum range from 0.3 GeV/c to 12 GeV/c. During the design phase, multiple simulation tools and techniques have been employed to optimize the tertiary beam line layout in terms of particle production, transverse beam dynamics and particle identification on an event-by-event basis. In this paper, a comparison of the simulated performance and the first measurement results obtained during the commissioning phase are presented.

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reference for this paper ※ https://doi.org/10.18429/JACoW-IPAC2019-THPGW064

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paper received ※ 24 April 2019 paper accepted ※ 18 May 2019 issue date ※ 21 June 2019

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THPGW069

Implementation of CERN Secondary Beam Lines T9 and T10 in BDSIM

target, optics, secondary-beams, software

3746

G. D’Alessandro, S.T. Boogert, S.M. Gibson, L.J. Nevay, W. Shields
JAI, Egham, Surrey, United Kingdom
J. Bernhard, A. Gerbershagen, M.S. Rosenthal
CERN, Geneva, Switzerland

CERN has a unique set of secondary beam lines, which deliver particle beams extracted from the PS and SPS accelerators after their interaction with a target, reaching energies up to 400 GeV. These beam lines provide a crucial contribution for test beam facilities and host several fixed target experiments. A correct operation of the beam lines requires precise simulations of the beam optics and studies on the beam-matter interaction, radiation protection, beam equipment survival etc. BDSIM combines tracking studies with energy deposition and beam-matter interaction simulations within one software framework. This paper presents studies conducted on secondary beams with BDSIM for the beam lines T9 and T10. We report the tracking analysis and the energy deposition along the beam line. Tracking analysis validation is demonstrated via comparison to existing code.

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reference for this paper ※ https://doi.org/10.18429/JACoW-IPAC2019-THPGW069

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paper received ※ 30 April 2019 paper accepted ※ 21 May 2019 issue date ※ 21 June 2019

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THPGW072

Seeded Self-Modulation of Transversely Asymmetric Long Proton Beams in Plasma

plasma, wakefield, proton, focusing

3757

T.A. Perera, C.P. Welsch
The University of Liverpool, Liverpool, United Kingdom
P. Muggli
MPI-P, München, Germany
T.A. Perera, C.P. Welsch
Cockcroft Institute, Warrington, Cheshire, United Kingdom

Funding: This work is supported by Science and Technology Facilities Council grant ST/P006752/1.
The AWAKE experiment at CERN recently demonstrated the world’s first acceleration of electrons in a proton-driven plasma wakefield accelerator*. Such accelerators show great promise for a new generation of linear e-p colliders using ~1-10 GV/m accelerating fields. Effectively driving a wakefield requires 100-fold self-modulation of the 12 cm Super Proton Synchrotron (SPS) proton beam using a plasma-driven process which must be care-fully controlled to saturation. Previous works have modelled this process assuming azimuthal symmetry of the transverse spatial and momentum profiles **, ***. In this work, 3D particle-in-cell simulations are used to model the self-modulation of such non-round beams. Implications of such effects for efficiently sustaining resonant wakefields are examined.
* Adli, E., et. al. (2018). Nature, 561(7723), 363-367.
** Lotov, K. V. (2015). Physics of Plasmas, 22(10), 103110.
*** Schroeder, C. B., et. al. (2011). Phys. Rev. Lett., 107(14).

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reference for this paper ※ https://doi.org/10.18429/JACoW-IPAC2019-THPGW072

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paper received ※ 15 May 2019 paper accepted ※ 23 May 2019 issue date ※ 21 June 2019

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THPGW078

Prototyping of Brazed mm-Wave Accelerating Structures

cavity, resonance, GUI, RF-structure

3764

M.A.K. Othman, B.J. Angier, A.A. Haase, E.A. Nanni, M.R. Roux, A.V. Sy
SLAC, Menlo Park, California, USA

Funding: This work was supported by Department of Energy contract DE-AC02-76SF00515. This work was also supported by NSF grants PHY-1734015.
Advanced fabrication and prototyping of metallic RF structures play a fundamental role in advancing accelerator technologies particularly at mm-wave and THz frequencies. With the scaling of the RF structure up to these frequencies, conventional fabrication techniques do not achieve the required accuracy and tolerances. Improved manufacturing techniques including diffusion bonding, brazing or clamping split-block geometries produce high quality structures when successfully implemented. However, in most schemes the resulting gap and irregularities at the iris result in a local field enhancement which is not desirable for high-gradient operation. Development of advanced split-block braze technique for THz accelerators was required for high quality miniature accelerators. A new braze technique was developed for W-band structures to control the flow of braze alloy, enabling fabrication of the first high-gradient brazed structures at mm-wave frequencies. This fabrication process has the potential to overcome consistent fabrication defects around the cell iris. Thin spacers were used to set the final gap between blocks during the braze process; while braze foil thickness is varied with minimal impact on the resulting frequency. To demonstrate the robustness of this technique, testing after the various manufacturing steps was done to monitor and track frequency change throughout the process. This technique is further pushed to produce G-band RF structures, operating at 300 GHz.

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reference for this paper ※ https://doi.org/10.18429/JACoW-IPAC2019-THPGW078

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paper received ※ 15 May 2019 paper accepted ※ 22 May 2019 issue date ※ 21 June 2019

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THPGW095

Characterization of REX/HIE-ISOLDE RFQ Longitudinal Acceptance and Transmission

rfq, ISOL, detector, linac

3789

N. Bidault, E. Matli, J.A. Rodriguez
CERN, Meyrin, Switzerland

The Isotope mass Separator On-Line DEvice (ISOLDE) based at CERN, is a Radioactive Ion Beam (RIB) facility where rare isotopes are produced from 1.4 GeV-proton collisions onto a target then are manipulated and transported to user experimental stations for studies, notably in the domain of nuclear physics. The RIB of interest is delivered to a dedicated experimental station either at low (up to 60 keV) or high energy (MeV/u range) after acceleration through the recently completed REX/HIE-ISOLDE linac upgrade. The first stage of the linac consists of normal-conducting IH and spiral-resonators and is preceded by a Radio-Frequency Quadrupole (RFQ). A description of the experimental setup and the specifications of the RFQ will serve as an introduction for the presentation of recent results about the transmission efficiency of the RFQ. Furthermore, a newly developed technique will be demonstrated, that allow the capture of ion beam intensities below the femto-Ampere range. In fine, a measurement of the longitudinal acceptance of the RFQ will be included.

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reference for this paper ※ https://doi.org/10.18429/JACoW-IPAC2019-THPGW095

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paper received ※ 13 May 2019 paper accepted ※ 23 May 2019 issue date ※ 21 June 2019

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THPRB011

Norm-optimal Iterative Learning Control to Cancel Beam Loading Effect on the Accelerating Field

controls, beam-loading, cavity, feedback

3824

Z. Shahriari, K. Fong
TRIUMF, Vancouver, Canada
G.A. Dumont
UBC, Vancouver, Canada

Iterative learning control (ILC) is an open loop control strategy that improves the performance of a repetitive system through learning from previous iterations. ILC can be used to compensate for a repetitive disturbance like the beam loading effect in resonators. In this work, we aim to use norm-optimal ILC to cancel beam loading effect. Norm-optimal ILC updates the control signal with the goal of minimizing a performance index, which results in monotonic convergence. Simulation results show that this controller improves beam loading compensation compared to a PI controller.

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reference for this paper ※ https://doi.org/10.18429/JACoW-IPAC2019-THPRB011

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paper received ※ 14 May 2019 paper accepted ※ 19 May 2019 issue date ※ 21 June 2019

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THPRB019

Collimation of Target Induced Halo Following MAGIX at MESA

target, beam-losses, experiment, cryomodule

3839

B. Ledroit
IKP, Mainz, Germany
K. Aulenbacher
KPH, Mainz, Germany
K. Aulenbacher
GSI, Darmstadt, Germany
K. Aulenbacher
HIM, Mainz, Germany

Funding: Supported by the DFG through GRK 2128
The Mainz Energy-recovering Superconducting Accelerator (MESA) will be an electron accelerator allowing operation in energy-recovery linac (ERL) mode. It provides the opportunity to operate scattering experiments at energies of ~100 MeV with thin gas-targets. The MESA Internal Gas Target Experiment (MAGIX) aims to operate windowless jet targets and different gases up to Xenon to search for possible dark photon interactions, to precisely measure the magnetic proton radius and astrophysical S-factors. Investigations on the impact of the target on beam dynamics and beam losses are required for machine safety and to examine limits to ERL operation. The goal of this work is to understand target induced halo in the different experimental setups, track halo particles through downstream sections to examine beam losses and include a suitable collimation system and shielding into the accelerator layout to protect the machine from direct and indirect damage through beam losses and radiation. The present status of the investigations is presented.

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reference for this paper ※ https://doi.org/10.18429/JACoW-IPAC2019-THPRB019

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paper received ※ 30 April 2019 paper accepted ※ 22 May 2019 issue date ※ 21 June 2019

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THPRB022

Sensitivity Analysis of Feedforward Beam Current Compensation for Improved Beam Loading Robustness

cavity, emittance, controls, injection

3850

D. Mihailescu Stoica, D. Domont-Yankulova
RMR, TU Darmstadt, Darmstadt, Germany
D. Domont-Yankulova, H. Klingbeil
TEMF, TU Darmstadt, Darmstadt, Germany
H. Klingbeil, D.E.M. Lens
GSI, Darmstadt, Germany

The planned SIS100 heavy ion synchrotron at the Facility for Antiproton and Ion Research (FAIR) in Darmstadt, Germany will possess twenty ferrite accelerating cavities in its final stage of extension. During the intended acceleration cycles, the cavities will encounter significant beam loading effects, which have to be handled by the control systems. As both the generator- and beam-current act on the same system input, a feedforward disturbance compensation can be a promising approach to improve beam qualities and suppress instabilities induced by the beam current. Particle tracking simulations, incorporating twenty ferrite cavities and their attached LLRF control systems, are performed to analyse the sensitivity of the beam quality with respect to errors in the feedforward beam current compensation. The main focus lies on the time after injection from a pre-accelerator, where most cavities in the SIS100 do not provide any gap voltage and thus are particularly sensitive to induced voltages by beam currents if the cavities are not or only partly short-circuited.

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reference for this paper ※ https://doi.org/10.18429/JACoW-IPAC2019-THPRB022

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paper received ※ 10 May 2019 paper accepted ※ 22 May 2019 issue date ※ 21 June 2019

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THPRB026

A 300 mm Long Prototype Strip-Line Kicker for the Heps Injection System

kicker, vacuum, injection, impedance

3864

L. Wang, J. Chen, L. Huo, P. Liu, H. Shi, X.L. Shi, G. Wang, N. Wang
IHEP, Beijing, People’s Republic of China

In the High Energy Photon Source (HEPS), the dynamic aperture of machine is not large enough for off-axis injec-tion for its baseline 7BA lattice design. So, a group of superfast kickers with about 12 ns pulse bottom width are needed for on-axis swap out injection scheme. The design about a couple sets of 300 mm long strip-line kickers is presented. Five kickers as a module are placed in a stain-less steel vacuum vessel to solve the problem of longitu-dinal space restriction in injection area. So far, the proto-type development of strip-line kicker was completed. The results of time-domain reflectometer (TDR) test and high voltage pulse test show that the strip-line kicker can meet the requirement of the HEPS.

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reference for this paper ※ https://doi.org/10.18429/JACoW-IPAC2019-THPRB026

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paper received ※ 06 May 2019 paper accepted ※ 21 May 2019 issue date ※ 21 June 2019

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THPRB043

Design and Simulation of Thin Eddy-Current Septum for Injection of Diffraction Limited Storage Ring

septum, injection, HOM, storage-ring

3908

J. Tong, M. Gu, B. Liu, Y.F. Liu, R. Wang
SINAP, Shanghai, People’s Republic of China

Funding: Work supported by the National Key Research and Development Program of China(Grant No.2016YFA0402002)
Ultra-low emittance in Diffraction Limited Storage Ring (DLSR) usually has small Dynamic Aperture (DA), which makes the traditional off-axis injection inadequate. Fast kickers together with thin septum magnets or direct current lambertsons could support on-axis injection for closely-spaced bunches with small DA. Thin eddy-current septum prototype had been designed for injection with laminated silicon steel sheets as magnet core. Theoretical analysis and transient simulation had been carried out within OPERA software. Due to the minimum thickness of the septa is only 1 mm , several optimization approaches had been applied, such as shielding with strongly paramagnetic material and exciting with full cycle driving pulse, to satisfy the requirement that the leakage field is less than 0.1% with respect to the main one.

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reference for this paper ※ https://doi.org/10.18429/JACoW-IPAC2019-THPRB043

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paper received ※ 29 April 2019 paper accepted ※ 21 May 2019 issue date ※ 21 June 2019

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THPRB049

MODELING AND SIMULATION FOR MULTI-FEEDING CAVITY WITHOUT BEAM LOADING

cavity, electron, impedance, beam-loading

3921

K. Liu, Q. Gu, L. Li, Ch. Wang, M.H. Zhao
SINAP, Shanghai, People’s Republic of China
Q. Gu
SSRF, Shanghai, People’s Republic of China

The Multi-feeding cavity usually be applied in super-conducting and normal-conducting RF cavity. The differences between multiple input couplers in coupler coefficient, incident power and phase will cause the cavity field stabilities can not meet the requirements. For explore the influences of these differences and develop equations for measurement, a multi-feeding LCR transient model was developed. As two-feeding cavity, the VHF photocathode electron gun was model and simulated in this paper.

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reference for this paper ※ https://doi.org/10.18429/JACoW-IPAC2019-THPRB049

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paper received ※ 06 May 2019 paper accepted ※ 22 May 2019 issue date ※ 21 June 2019

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THPRB056

Dose Measurement Experiments for Single and Composite Targets in 6 Mev Linear Accelerators

target, site, electron, experiment

3937

Z.H. Wang, J.Y. Liu, J. Shi, H. Zha
TUB, Beijing, People’s Republic of China

The target in electron linear accelerator plays an im-portant role in the production of photon. Targets of different materials and thicknesses have different X-ray yields. In this study, experiments were carried out to measure the dose rates of single targets and composite targets of different thicknesses for 6 MeV linear accel-erators utilizing ionization chamber. The electron ener-gy spectrum at the outlet of accelerating tube was de-tected with magnetic analyser. The experimental results show consistent rules with Monte Carlo simulations. Composite material target of 1.2 mm tungsten and 2 mm copper can deliver 1242 rad/min/100uA dose rate at 1 meter in front of the target. Dose rates of tungsten- rhenium alloy(74%W-26%rhenium) targets were exam-ined too.

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reference for this paper ※ https://doi.org/10.18429/JACoW-IPAC2019-THPRB056

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paper received ※ 14 May 2019 paper accepted ※ 21 May 2019 issue date ※ 21 June 2019

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THPRB062

New Orbit Correction Method Based on SVDC Algorithm for Ring Based Light Sources

feedback, lattice, controls, photon

3943

X.Y. Huang, J.S. Cao, Y.Y. Du, Y.H. Lu, H.Z. Ma, Y.F. Ma, Y.F. Sui, S.J. Wei, Y. Wei, Q. Ye, X.E. Zhang, D.C. Zhu
IHEP, Beijing, People’s Republic of China

Funding: Union Foundation of excellent post-doctoral of China
Orbit feedback system is essential for realizing the exceeding beam stability in modern ring based light sources. Most advanced light sources adopt the global correction scheme by using singular value decomposition (SVD) algorithm. In this paper, a new SVD with constraints method (SVDC) is proposed to correct the global and local orbit simultaneously. Numerical simulations are presented with the case of High Energy Light Source (HEPS) by comparing classic algorithms. The results show that SVDC is very effective for orbit correction and very easy to implement.

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reference for this paper ※ https://doi.org/10.18429/JACoW-IPAC2019-THPRB062

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paper received ※ 09 May 2019 paper accepted ※ 22 May 2019 issue date ※ 21 June 2019

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THPRB074

Studies Towards the New Beam Screen System of the LHC Injection Kicker Magnet for HL-LHC Operation

kicker, injection, operation, vacuum

3982

V. Vlachodimitropoulos, M.J. Barnes, A. Chmielinska, L. Ducimetière, L. Vega Cid, W.J.M. Weterings
CERN, Geneva, Switzerland
A. Chmielinska
EPFL, Lausanne, Switzerland
L. Vega Cid
ETSII UPM, Madrid, Spain

Although no heating issues were observed in the Large Hadron Collider’s (LHC) injection kicker magnets (MKIs) during Run 2, simulations suggest that for operation with the high intensity beams of the High Luminosity LHC (HL-LHC) project, the magnet’s ferrite yokes will reach their Curie temperature, thus leading to long turnaround times before a new beam can be safely injected into the machine. To safely enter the HL-LHC era, a campaign to redesign the kicker’s beam screen was launched. An improved beam-screen has already been implemented in an upgraded MKI, that was installed in the LHC tunnel in the Year End Technical Stop (YETS) 17/18, and has been successfully tested during 2018 operation. However, the improved design alone is not expected to be enough for HL-LHC operation, and further modifications are required. In this work, the approach to the design from an electromagnetic point of view is presented and different considered options are reported, emphasising the final design of the new beam screen system that is currently being implemented.

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reference for this paper ※ https://doi.org/10.18429/JACoW-IPAC2019-THPRB074

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paper received ※ 14 May 2019 paper accepted ※ 23 May 2019 issue date ※ 21 June 2019

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THPRB075

Transverse Impedance Measurements and Simulations of the LHC Injection Kicker Magnet

impedance, kicker, injection, coupling

3986

V. Vlachodimitropoulos, M.J. Barnes, A. Chmielinska, L. Ducimetière
CERN, Geneva, Switzerland
A. Chmielinska
EPFL, Lausanne, Switzerland

Kicker magnets contribute significantly to the total impedance budget of many accelerators. Of particular interest, from a beam stability point of view, is the transverse beam coupling impedance (TBCI) that is used to determine intensity limitations of a machine. Until recently, no conclusive TBCI data for the Large Hadron Collider (LHC) injection kicker magnets (MKIs) was available. However, in view of the upgrade of the MKIs for the High-Luminosity LHC (HL-LHC) project, the TBCI of the existing design needed to be estimated to be used as reference for an upgraded version. To that end, electromagnetic simulations were carried out to determine the dipolar and quadrupolar components of the TBCI in the two transverse planes. To validate the simulations, test bench measurements were performed using standard RF measurement techniques. In the present work, the results from TBCI simulations and measurements are reported and compared. Detailed descriptions of the methods and techniques used as well as the realization of the experimental set-up are also given.

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reference for this paper ※ https://doi.org/10.18429/JACoW-IPAC2019-THPRB075

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paper received ※ 14 May 2019 paper accepted ※ 22 May 2019 issue date ※ 21 June 2019

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THPRB077

Optics Corrections Using Machine Learning in the LHC

optics, network, quadrupole, controls

3990

E. Fol, J.M. Coello de Portugal, R. Tomás
CERN, Meyrin, Switzerland
G. Franchetti
GSI, Darmstadt, Germany

Optics corrections in the LHC are based on a response matrix approach between available correctors and observables. Supervised learning has been applied to quadrupole error prediction at the LHC giving promising results in simulations and surpassing the performance of the traditional approach. A comparison of different algorithms is given and it is followed by the presentation of further possible concepts to obtain optics corrections using machine learning.

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reference for this paper ※ https://doi.org/10.18429/JACoW-IPAC2019-THPRB077

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paper received ※ 14 May 2019 paper accepted ※ 21 May 2019 issue date ※ 21 June 2019

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THPRB078

Performance Validation of the Existing and Upgraded PS Injection Kicker

kicker, injection, flattop, operation

3994

A. Ferrero Colomo, N. Ayala, A. Chmielinska, V. Forte, M.A. Fraser, T. Kramer, L. Sermeus
CERN, Geneva, Switzerland

The CERN PS injection kicker KFA45 will be upgraded in the framework of the LHC Injector Upgrade (LIU) project to allow for injection of 2 GeV proton beams. This paper summarizes the recent efforts to validate beam based waveform measurements, Pspice simulations and current waveform measurements by direct magnetic field measurements in the aperture of the existing system. The magnetic probe, associated measurement hardware design and measurements results are discussed. The paper concludes with a performance comparison and an outlook to future waveform tuning possibilities.

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reference for this paper ※ https://doi.org/10.18429/JACoW-IPAC2019-THPRB078

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paper received ※ 14 May 2019 paper accepted ※ 22 May 2019 issue date ※ 21 June 2019

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THPRB080

Automatisation of the SPS ElectroStatic Septa Alignment

alignment, extraction, operation, septum

4001

S. Hirlaender
ATI, Vienna, Austria
M.A. Fraser, B. Goddard, V. Kain, J. Prieto, L.S. Stoel, F.M. Velotti
CERN, Geneva, Switzerland
M. Szakaly
Wigner Research Centre for Physics, Institute for Particle and Nuclear Physics, Budapest, Hungary

An electrostatic septum composed of 5 separate tanks is used to slow-extract the 400 GeV proton beam resonantly on the third integer resonance from the CERN SPS. The septa are all mounted on a single support structure that can move the ensemble coherently and, in addition, the internal anode and cathode of each tank can be moved independently. The septum is aligned to the beam by measuring and minimising the induced beam loss signals in the extraction region following an alignment procedure that is usually carried out manually at the beginning of each year. The large number of positional degrees of freedom complicates the procedure and until recently each tank was aligned one after the other semi-manually, typically requiring 8 hours. It is not uncommon that the septum has to be re-aligned later in the run taking time away from physics programme. To tackle this issue, a simplified beam dynamics and scattering simulation routine was developed to permit error studies with a large number of seeds to be carried out in a reasonable computation time. In this contribution, the simulation model will be described before the results of its exploitation to understand the efficacy of alignment procedures based on different optimization algorithms are discussed and compared to the present operational procedure. The effort culminated with the implementation of an automated alignment procedure based on a Powell optimisation algorithm that reduced the time needed to align the septum by over an order of magnitude.

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reference for this paper ※ https://doi.org/10.18429/JACoW-IPAC2019-THPRB080

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paper received ※ 14 May 2019 paper accepted ※ 22 May 2019 issue date ※ 21 June 2019

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THPRB094

Study of the System Stability for the Digital Low Level RF System Operated at High Beam Currents

cavity, LLRF, controls, feedback

4042

Z.K. Liu, F.Y. Chang, L.-H. Chang, M.H. Chang, S.W. Chang, L.J. Chen, F.-T. Chung, Y.T. Li, M.-C. Lin, C.H. Lo, Ch. Wang, M.-S. Yeh, T.-C. Yu
NSRRC, Hsinchu, Taiwan

The purpose of a Low-Level Radio Frequency (LLRF) system is to control the amplitude and phase of the field in the accelerating cavity. A digital LLRF (DLLRF) system will be installed in the Taiwan Photon Source (TPS) storage ring in 2019. The system stability depends much on the feedback parameters. An instability of the cavity voltage controlled by a DLLRF was observed during machine tests with high beam current and low feedback gain. A simulation model for the digital LLRF system with beam-cavity interaction was developed to investigate this instability and simulations and machine test results will be presented here.

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reference for this paper ※ https://doi.org/10.18429/JACoW-IPAC2019-THPRB094

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paper received ※ 07 May 2019 paper accepted ※ 23 May 2019 issue date ※ 21 June 2019

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THPRB095

A Simulation Framework for Photon-Particle Interactions for Laserwires and Further Applications

laser, photon, electron, scattering

4045

S.E. Alden, S.M. Gibson, L.J. Nevay
JAI, Egham, Surrey, United Kingdom

A model has been developed for simulating photon-particle interactions with Beam Delivery Simulation (BDSIM). BDSIM is a high energy physics program that utilises the Geant4, CLHEP, and ROOT libraries to seamlessly track particles through an accelerator. The photon-particle interactions introduce the capability for modelling a range of applications in accelerator physics. One such application is a laserwire which is a minimally invasive diagnostic technique to measure beam profiles and emittance. In this paper we describe the recent implementation of inverse Compton scattering and electron stripping of Hydrogen ions. This is demonstrated on an example beamline.

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reference for this paper ※ https://doi.org/10.18429/JACoW-IPAC2019-THPRB095

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paper received ※ 15 May 2019 paper accepted ※ 22 May 2019 issue date ※ 21 June 2019

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THPRB100

A Generic Software Platform for Rapid Prototyping of Online Control Algorithms

controls, software, interface, EPICS

4063

C.J.R. Duncan, M.B. Andorf, I.V. Bazarov, I.V. Bazarov, C.M. Gulliford, V. Khachatryan, J.M. Maxson, D.L. Rubin
Cornell University (CLASSE), Cornell Laboratory for Accelerator-Based Sciences and Education, Ithaca, New York, USA
I.V. Bazarov
Cornell University, Ithaca, New York, USA

Funding: US Department of Energy DE-SC 0013571
Algorithmic control of accelerators is an active area of research that promises significant improvements in machine performance. To facilitate rapid algorithm prototyping, we have developed a generic interface between accelerator controls, beam physics modelling software and modern scripting languages. The work-flow of a project using this interface begins with testing algorithms of choice offline in simulation. After off-line testing, the same code can be deployed on real machines via the Experimental Physics and Industrial Control System (EPICS) API. We include noise in our simulations in order to mimic realistic accelerator behaviour and to evaluate robustness of algorithms to experimental uncertainties and long-term drifts. The results of test cases of using this framework are presented, including emittance tuning of the Cornell Electron Storage Ring (CESR), correction of diurnal drift in CESR steering and orbit correction on CESR and the Cornell-BNL ERL Test Accelerator (CBETA).

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reference for this paper ※ https://doi.org/10.18429/JACoW-IPAC2019-THPRB100

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paper received ※ 14 May 2019 paper accepted ※ 23 May 2019 issue date ※ 21 June 2019

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THPRB102

Monte Carlo Optimization of Fast Beam Loss Monitors for LCLS-II

detector, target, photon, electron

4066

M. Santana-Leitner, C.I. Clarke, A.S. Fisher, A.M. Harris, C. Hast, T.T. Liang
SLAC, Menlo Park, California, USA
E. Griesmayer
CIVIDEC Instrumentation, Wien, Austria

Funding: Work supported by U.S. Department of Energy contract DE-AC02-76SF00515
Commissioning of the LCLS-II hard X-ray FEL is starting at SLAC National Accelerator Laboratory. This facility will ultimately accelerate electrons to 8 GeV, with beams of 375 kW at 1 MHz. At such high-powers, errant beams will need to be detected very fast -200 μs- to limit exposure and to protect beam-line and safety components. Currently, LCLS-I uses ion chambers both as Point Beam Loss Monitors (PBLM) by collimators, dumps, septa, etc., and also as Long Beam Loss Monitors (LBML) that provide detection coverage in extended areas where the accelerator enclosure is not sufficiently thick to shield full beam losses. But due to the finite ion mobility and related screening effects, ion chambers are not fast enough, and their response would not be linear at high charge rates. LCLS-II will use synthetic mono-crystalline diamond chips as PBLMs, as those offer nanosecond time resolution due to the high mobility of holes generated in the valence band by charged particles. LBLMs will be 200 m-long optical fibers, with photomultipliers to detect Cerenkov photons produced by charged particles in the fibers. Use of these technologies requires tests and models to correlate their response to different beam losses. Response functions for these detectors have been developed for the FLUKA Monte Carlo code. After benchmarking the models, these have been applied to place PBLMs at locations where signal is relatively insensitive to beam-strike uncertainties and sufficiently above electronic noise, while keeping lifetime to radiation-damage long. Also, topologies where found were one PBLM can protect several components, resulting in cost reductions. As for LBLMs, the existing model helps scale signals for different beam loss configurations as a function of the fiber position.

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reference for this paper ※ https://doi.org/10.18429/JACoW-IPAC2019-THPRB102

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paper received ※ 14 May 2019 paper accepted ※ 22 May 2019 issue date ※ 21 June 2019

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THPRB108

LBNF Hadron Absorber: Updated Mechanical Design and Analysis for 2.4 MW Operation

operation, hadron, site, shielding

4078

A. Deshpande, K. Anderson, K.E. Gollwitzer, B.D. Hartsell, J. Hylen, V.I. Sidorov, S. Tariq
Fermilab, Batavia, Illinois, USA

The Long-Baseline Neutrino Facility (LBNF) Hadron Absorber is located downstream of the decay pipe. It consists of actively cooled aluminum and steel blocks surrounded by steel and concrete shielding. Majority of the beam power is deposited in the absorber core which is water cooled. The surrounding steel and concrete shielding are air-cooled. The absorber provides radiation protection to personnel and keeps soil and ground activation levels to below allowable limits. It is designed for 2.4 MW beam operations. The total heat load deposited into the absorber is approximately 400 kW. The current design considers the longer 4-interaction length target of the optimized beam design. In addition, the ‘bafflette’ around the target reduces the energy deposited into the absorber. For this reason, the sculpting in the aluminum core blocks, which was in the previous design, was removed, making the design uniform and less complicated. In addition, the uniformity of the absorber makes it easier to understand the muon monitor data. Steady state thermal, structural, and Computational Fluid Dynamics (CFD) analysis of critical absorber aluminum and steel components during steady state operations is discussed herein. A similar analysis for a 120 GeV, 10 µs pulse, accident condition is also discussed. A preliminary design for the accident pulse prevention system that protects the absorber is also described.

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reference for this paper ※ https://doi.org/10.18429/JACoW-IPAC2019-THPRB108

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paper received ※ 30 April 2019 paper accepted ※ 23 May 2019 issue date ※ 21 June 2019

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THPTS007

MYRRHA 80 kW CW RF Coupler Design

cavity, multipactoring, electron, vacuum

4115

Y. Gómez Martínez, M.A. Baylac, D. Bondoux, F. Bouly, P.-O. Dumont
LPSC, Grenoble Cedex, France
S. Blivet, C. Joly, J. Lesrel, H. Saugnac
IPN, Orsay, France
W. Kaabi
LAL, Orsay, France

MYRRHA [1] (Multi Purpose Hybrid Reactor for High Tech Applications) is an Accelerator Driven System (ADS) project. Its superconducting linac will provide a 600 MeV - 4 mA proton beam. The first project phase based on a 100 MeV linac is launched. The Radio-Frequency (RF) couplers have been designed to handle 80 kW CW at 352.2 MHz. This paper describes the thermal, mechanical and RF studies leading to the final design of the RF coupler.

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reference for this paper ※ https://doi.org/10.18429/JACoW-IPAC2019-THPTS007

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paper received ※ 10 May 2019 paper accepted ※ 23 May 2019 issue date ※ 21 June 2019

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THPTS009

High-Current Emittance Measurements at MAMI

emittance, quadrupole, electron, experiment

4121

S. Heidrich, K. Aulenbacher, M. Dehn, P. Heil
IKP, Mainz, Germany
M.W. Bruker
HIM, Mainz, Germany

Funding: Work supported by BMBF-Verbundforschung Verbundprojekt 05H2015UMRB1, R&D Beschleuniger (Positronenquellen)
The effects of high beam currents and different types of electron sources on the emittance of the beam at the 3.5 MeV beamline of the Mainzer Microtron MAMI were observed. A thermionic BaO source and a GaAs-based photo-source that allows spin polarization were used. In order to measure the beam size, a new type of wire scanner was utilized. The results show maximum normalized emittance values in the order of a few hundred nmrad for both sources, which lies distinctly within the acceptance of the higher energy stages of the accelerator.

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reference for this paper ※ https://doi.org/10.18429/JACoW-IPAC2019-THPTS009

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paper received ※ 14 May 2019 paper accepted ※ 23 May 2019 issue date ※ 21 June 2019

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THPTS013

Further Designs of HOM Couplers for Superconducting 400 MHz RF Cavities

cavity, HOM, impedance, proton

4132

N.F. Petry, M. Busch, K. Kümpel, O. Meusel, H. Podlech
IAP, Frankfurt am Main, Germany

The Future Circular Collider (FCC) is one possible future successor of the Large Hadron Collider (LHC) at CERN. The proton-proton collider center-of-mass collision energy is set to 100 TeV with a beam current of 0.5 A. To achieve this energy a stable acceleration is critical and therefore higher order modes (HOM) need to be damped. HOM dampers, further characterized as couplers, need to fulfill several criteria to be efficient. As a first property the couplers should assure a longitudinal impedance of higher order modes of below 10 kW. Furthermore, the loaded Q-factor should be below 1000 and the corresponding R/Q value should be in the range of 10 Ω. Besides the Hook-type and Probe-type HOM coupler two additional designs were simulated. The recent results of the different couplers attached to a superconducting 400 MHz RF cavity will be presented.

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reference for this paper ※ https://doi.org/10.18429/JACoW-IPAC2019-THPTS013

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paper received ※ 09 May 2019 paper accepted ※ 23 May 2019 issue date ※ 21 June 2019

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THPTS014

Visual Inspection of Curved Particle Accelerator Beam Pipes with a Modular Robot

controls, dipole, experiment, vacuum

4135

N. Schweizer
RMR, TU Darmstadt, Darmstadt, Germany
I. Pongrac
GSI, Darmstadt, Germany

Inspecting ultra-high vacuum pipe systems of particle accelerators without disassembling the beam pipes is a complex challenge. In particular, curved sections of particle accelerators require a unique approach for the examination of the interior. For the planned heavy ion synchrotron SIS100 at FAIR, an inspection robot is currently under development, featuring an optical imaging system with which the robot can be navigated through the beam pipe. We present the current prototype, which is based on a modular snake-like robot with active wheels and joints. Due to the stipulated low movement velocity, it can be shown that a kinematic model is sufficient to control the robot whereas dynamical effects can be neglected. This concept is proven in experiments with the prototype. At the current development status, the robot is controlled manually by setting the velocity of the first module and its desired turning angle. In simulations we include a CAD model of a dipole chamber of the SIS100 and let an operator successfully navigate the robot through the beam pipe while only observing the camera image.

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reference for this paper ※ https://doi.org/10.18429/JACoW-IPAC2019-THPTS014

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paper received ※ 14 May 2019 paper accepted ※ 21 May 2019 issue date ※ 21 June 2019

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THPTS019

Design of Beam Position Monitoring System for IPM Low Energy Electron LINAC

cavity, electron, software, linac

4394

N. Messbah, F. Abbasi Davani
Shahid Beheshti University, Tehran, Iran
S. Ahmadiannamin
ILSF, Tehran, Iran
H. Shaker, M. Shirshekan
IPM, Tehran, Iran

A beam position monitor (BPM) is a common device used in particle accelerators to measure the position of a beam of charged-particles. The goal of this project is to simulate and build prototype of different parts to be used for IPM low energy electron Linac being developed at Institute for Research in Fundamental Sciences. The IPM low energy electron Linac will initially be operated at a 7𝜇sec pulse duration and 250 Hz repetition rate with 2.998 GHz bunching frequency. A 4.5-MeV electron beam will be available in the second phase of commissioning. The device is composed of two pickup S-band cavities and a detection circuit to read out the electron beam’s position. The electrode pickup sensors will sense the mode strength generated by the passing beam of electrons. The working modes are TM110 (dipole) for the so called position cavity and TM010 (monopole) for the reference cavity. When the beam crosses the two cavity gaps it induces signals proportional to the product of charge and position offset in the position cavity, and to the charge only in the reference cavity. the position cavity has four rectangular waveguides that couple to the dipole mode while rejecting the monopole mode that would otherwise limit the resolution of the electronics. This signal will be input to a detection circuit that will be used to calculate the signals detected by four antennas arranged. A 180 degree hybrid at the first stage reduce the monopole and a heterodyne receiver principle was used to down-convert the signal frequency in about MHz IF frequency. These signals can then be used to determine the beam’s displacement from the center.

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reference for this paper ※ https://doi.org/10.18429/JACoW-IPAC2019-THPTS019

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paper received ※ 15 May 2019 paper accepted ※ 24 May 2019 issue date ※ 21 June 2019

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THPTS031

Simulations of the Activation of a Proton Therapy Facility Using a Complete Beamline Model With BDSIM

proton, neutron, shielding, experiment

4176

R. Tesse, E. Gnacadja, C. Hernalsteens, N. Pauly
ULB - FSA - SMN, Bruxelles, Belgium
S.T. Boogert, L.J. Nevay, W. Shields
JAI, Egham, Surrey, United Kingdom
C. Hernalsteens
IBA, Louvain-la-Neuve, Belgium

A detailed model of the IBA Proteus One compact gantry system has been created with BDSIM (Beam Delivery Simulation) that has been validated against experimental data. Results regarding activation studies have been obtained for the first time using seamless simulations of the transport of protons in the beamline and their interactions with the environment. The activation of the concrete shielding of the system is estimated after a period of 20 years of operation. These main results are presented and discussed in detail.

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reference for this paper ※ https://doi.org/10.18429/JACoW-IPAC2019-THPTS031

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paper received ※ 15 May 2019 paper accepted ※ 22 May 2019 issue date ※ 21 June 2019

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THPTS034

Design and Progress of Mechanical Support in HEPS

alignment, storage-ring, synchrotron, emittance

4180

C.H. Li, Y. Jiao, M.X. Li, H. Wang, Z. Wang, L. Wu, N. Zhou
IHEP, Beijing, People’s Republic of China

HEPS is a new generation synchrotron facility on construction with very low emittance. Stringent requirements are proposed to the design of mechanical support. The alignment error between girders should be less than 50μm. Based on that, the adjusting resolution of the girder are required to be less than 5μm in both transverse and vertical directions. Besides, the Eigen frequency of magnet & girder assembly should be higher than 54Hz to avoid the amplification of ground vibrations. To fulfill these requirements, studies on mechanical support design is now being carried out in HEPS. This paper will describe the design and progress of those work.

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reference for this paper ※ https://doi.org/10.18429/JACoW-IPAC2019-THPTS034

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paper received ※ 14 May 2019 paper accepted ※ 23 May 2019 issue date ※ 21 June 2019

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THPTS037

The Deformation-Stress Simulation and Measurement of Titanium Foil Strip for Hadron Monitor

electron, experiment, hadron, ECR

4187

A.X. Wang, J.X. Chen, H.Y. He, L. Liu, X.J. Nie, C.J. Ning, J.L. Sun, G.Y. Wang, J.B. Yu, Y.J. Yu, J.S. Zhang, D.H. Zhu
IHEP CSNS, Guangdong Province, People’s Republic of China
L. Kang
IHEP, Beijing, People’s Republic of China

The measurement of beam profile by hadron monitor is in fact the measurement of the positive current after the secondary electrons escaped. According to the situation that the number of beam particles is small and the current signal is weak, the material titanium with high secondary electron generation rate is select by material comparison, and the foil strip type is used to increase the cross section area to obtain lager current level. On account of dead weight itself, as well as thermal expansion and contraction, the foil strip shall be loose. The loosen strip will deviate from its theoretical position, and cause the measuring error. Therefore, the deformation-stress of Ti foil strip (1000*50*0.1) was simulated under the pretension (10~90N) with the finite element software ANSYS. A set of experiment device with pretension adjustment and heating for the foil strip was designed, and then the deformation-stress was tested by a high precision 3-D imaging measurement system. Compared with the simulation results, the pretension would better set at about 50N.

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reference for this paper ※ https://doi.org/10.18429/JACoW-IPAC2019-THPTS037

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paper received ※ 12 May 2019 paper accepted ※ 19 May 2019 issue date ※ 21 June 2019

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THPTS038

There-Dimensional Simulation of a C-Band 32-Beam Klystron

klystron, electron, cavity, bunching

4190

Z.N. Liu, H.B. Chen, J. Shi, H. Zha
TUB, Beijing, People’s Republic of China

A 32-beam klystron working at 5.712 GHz has been designed with efficiency of 70% and output power of 3.4 MW. Core oscillations method (COM) is chosen to bunch electrons. The code KlyC is used for 1-D and 1.5-D calculation and a series of parameters are given after optimizing, including the position, frequency, R/Q, Q₀ and Qe of cavities. CST/PIC is used to make the final design and coaxial cavities are used. This paper describes 1-D, 1.5-D and 3-D beam dynamics of the klystron, compares their differences, and analyses effect of these differences on efficiency.

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reference for this paper ※ https://doi.org/10.18429/JACoW-IPAC2019-THPTS038

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paper received ※ 15 May 2019 paper accepted ※ 22 May 2019 issue date ※ 21 June 2019

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THPTS043

PRELIMINARY MAGNETIC FIELD CALCULATION OF A 30-DEGREE DIPOLE MAGNET

dipole, proton, operation, laser

4204

H. Liang, J. Huang, C. Jiang, T. Liu, B. Qin, K. Tang, J. Yang, J.Q. Ye
HUST, Wuhan, People’s Republic of China
Y. Xie, T. Yu
Huazhong University of Science and Technology, State Key Laboratory of Advanced Electromagnetic Engineering and Technology,, Hubei, People’s Republic of China

Preliminary design and field calculation of a 30-degree H-type dipole which can be applied to the beamline is introduced in this paper. According to the phys-ical requirements, 2D and 3D models are built and ana-lysed using OPERA. For achieving the magnetic field specifications, air slots are adopted, and trapezoidal shim on pole surface is used to improve the magnetic field error. Rogowski curve and harmonic shim at the pole end is used to reduce the integral magnetic field error and the higher order harmonic field error.

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reference for this paper ※ https://doi.org/10.18429/JACoW-IPAC2019-THPTS043

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paper received ※ 13 May 2019 paper accepted ※ 23 May 2019 issue date ※ 21 June 2019

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THPTS046

The Limited B-Field Integral of Superconducting Longitudinal Gradient Bend Magnet

emittance, storage-ring, synchrotron-radiation, radiation

4213

C. Chen, L. Wang, H.R. Zhang, T. Zhang
USTC/NSRL, Hefei, Anhui, People’s Republic of China

The National Synchrotron Radiation Laboratory (NSRL) is planning a fourth generation diffraction-limited light source–Hefei Advanced Light Source (HALS), it is based on a seven-bend achromat lattice providing an ultralow natural emittance of 34 pm rad. The emittance can be even lower with the use of longitudinal gradient bends (LGBs) and anti-bends (ABs). The designed energy for HALS is 2.4 GeV, superconducting LGB might be employed instead of normal bending magnet since it can improve radiated beam critical energy to hard x-ray regions without using up any straight sections. To get a peak field about 6 T and small B-field profile full width half maximum, SLS-2 type LGB is considered. In this paper, the limited B-field integral (along the beam path) is trying to be find with some restrictions.

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reference for this paper ※ https://doi.org/10.18429/JACoW-IPAC2019-THPTS046

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paper received ※ 12 May 2019 paper accepted ※ 21 May 2019 issue date ※ 21 June 2019

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THPTS052

Beam Loss Suppression by Beam Matching in Klystron

klystron, gun, beam-losses, injection

4218

S.J. Park, Y.J. Park
PAL, Pohang, Kyungbuk, Republic of Korea
S.C. Cha, D.H. Kim, D.H. Yu
VITZRONEXTECH, Ansan-si, Gyeonggi-do, Republic of Korea
J.H. Hwang
POSTECH, Pohang, Kyungbuk, Republic of Korea

Funding: The work was supported by the National R&D Program (grant number: 2016R1A6B2A01016828) through the National Research Foundation of Korea (NRF) funded by the Ministry of Science and ICT in Korea.
High power klystrons usually employ large cathodes to generate high currents which are compressed inside the gun to provide optimum beam sizes at the cavity section. We compress the beam by using electrostatic and magnetostatic focusing fields which are established by gun electrodes and external magnets respectively. The geometry of the gun elecrodes and the external magnet is carefully designed to meet the matching condition which results in scalloping-free beam. We have established a systematic design procedures to achieve the beam matching condition at arbitrary beam sizes. In this article we report on the beam-matching design and simulation results with an example case of the 80-MW S-band klystron in the Pohang Accelerator Laboratory.

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reference for this paper ※ https://doi.org/10.18429/JACoW-IPAC2019-THPTS052

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paper received ※ 15 May 2019 paper accepted ※ 23 May 2019 issue date ※ 21 June 2019

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THPTS055

Design and Construction of 3D Helmholtz Coil System to Calibrate 3D Hall Probes

HOM, alignment, controls, dipole

4228

J. Marcos, J. Campmany, A. Fontanet, V. Massana, L.R.M. Ribó
ALBA-CELLS Synchrotron, Cerdanyola del Vallès, Spain

In this paper we present the design of a system of 3D Helmholtz coils aimed to generate a magnetic field in any direction in a controlled way. The system is intended to be applied to the detailed characterisation of the response of 3D Hall probes as a function of the orientation of the measured field. The system will generate magnetic fields of up to 5 mT with an expected angular precision of 0.2 mrad.

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reference for this paper ※ https://doi.org/10.18429/JACoW-IPAC2019-THPTS055

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paper received ※ 26 April 2019 paper accepted ※ 23 May 2019 issue date ※ 21 June 2019

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THPTS062

Alternative Proposal for FCC-hh Extraction Septa

septum, extraction, quadrupole, vacuum

4248

A. Sanz Ull, M.G. Atanasov, B. Balhan, J.C.C.M. Borburgh
CERN, Geneva, Switzerland

Challenging requirements are set for the FCC extraction septa magnets, notably for the magnetic field level, the septum thickness and the leak field. An alternative to the baseline FCC extraction layout with normal conducting Lambertson septa is proposed, consisting of a Superconducting Shield (SuShi) stage and a Truncated Cosine theta septa stage with the aim of reducing the necessary number of septa and installed length. The principal parameters of the septa are described and the feasibility discussed. Areas for study improvement are identified.
This paper is intended for publication in the PRAB special edition.

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reference for this paper ※ https://doi.org/10.18429/JACoW-IPAC2019-THPTS062

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paper received ※ 13 May 2019 paper accepted ※ 22 May 2019 issue date ※ 21 June 2019

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THPTS064

Sub-Picosecond X-Ray Streak Camera using High-Gradient RF Cavities

electron, cathode, photon, gun

4256

F. Toufexis, V.A. Dolgashev
SLAC, Menlo Park, California, USA

Funding: This project was funded by U.S. Department of Energy under Contract No. DE-AC02-76SF00515.
We are developing an ultrafast diagnostic system for X-ray beams from Synchrotron Light Sources and Free-Electron Lasers. In this system, the X-ray beam is focused on the photocathode of a high-gradient radio-frequency cavity that accelerates the photo-emitted electrons to a few MeV while preserving their time structure. The accelerated electron beam is streaked by radio-frequency deflectors and then imaged on a screen. This approach will allow orders of magnitude improvement in time resolution over traditional streak cameras and could potentially enable time-resolved diagnostics of sub-100 fs X-ray pulses. We present preliminary beam dynamics simulations of this system and discuss the implementation.

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reference for this paper ※ https://doi.org/10.18429/JACoW-IPAC2019-THPTS064

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paper received ※ 11 May 2019 paper accepted ※ 22 May 2019 issue date ※ 21 June 2019

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THPTS065

Analysis on the Thermal Response to Beam Impedance Heating of the Post Ls2 Proton Synchrotron Beam Dump

impedance, proton, site, wakefield

4260

L. Teofili, F. Giordano, I. Lamas, F.-X. Nuiry, G. Romagnoli, B. Salvant
CERN, Geneva, Switzerland
M. Marongiu, M. Migliorati
Sapienza University of Rome, Rome, Italy

The High Luminosity Large Hadron Collider (HL-LHC) and the LIU (LHC-Injection Upgrade) projects at CERN are upgrading the whole CERN accelerators chain, increasing beam brightness and intensity. In this scenario, some critical machine components have to be redesigned and rebuilt. Due to the increase in beam intensity, minimizing the electromagnetic interaction between the beam and the device is a crucial design task. Indeed, these interactions could lead to beam instabilities and excessive thermo-mechanical loadings in the device. In this context, this paper presents an example of multi-physics study to investigate the impedance related thermal effects. The analysis is performed on the conceptual design of the new proton synchrotron (PS) internal dump.

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reference for this paper ※ https://doi.org/10.18429/JACoW-IPAC2019-THPTS065

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paper received ※ 26 April 2019 paper accepted ※ 22 May 2019 issue date ※ 21 June 2019

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THPTS066

Beam Impact Experiment of 440GeV/p Protons on Superconducting Wires and Tapes in a Cryogenic Environment

experiment, proton, interface, cryogenics

4264

A. Will, A. Bernhard, A.-S. Müller
KIT, Karlsruhe, Germany
Y. Bastian, B. Bordini, M. Favre, B. Lindstrom, M. Mentink, A. Monteuuis, A. Oslandsbotn, R. Schmidt, A.P. Siemko, K. Stachon, M.P. Vaananen, A.P. Verweij, A. Will, D. Wollmann
CERN, Geneva, Switzerland
M. Bonura, C. Senatore
UNIGE, Geneva, Switzerland
A. Usoskin
BRUKER HTS GmbH, Alzenau, Germany

The superconducting magnets used in high energy particle accelerators such as CERN’s LHC can be impacted by the circulating beam in case of specific failure cases. This leads to interaction of the beam particles with the magnet components, like the superconducting coils, directly or via secondary particle showers. The interaction leads to energy deposition in the timescale of microseconds and induces large thermal gradients within the superconductors in the order of 100 K/mm. To investigate the effect on the superconductors, an experiment at CERN’s HiRadMat facility was designed and executed, exposing short samples of Nb-Ti and Nb₃Sn strands as well as YBCO tape in a cryogenic environment to microsecond 440 GeV/p proton beams. The irradiated samples were extracted and are being analyzed for their superconducting properties, such as the critical transport current. This paper describes the experimental setup as well as the first results of the visual inspection of the samples.

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reference for this paper ※ https://doi.org/10.18429/JACoW-IPAC2019-THPTS066

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paper received ※ 13 May 2019 paper accepted ※ 23 May 2019 issue date ※ 21 June 2019

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THPTS072

Field Measurements for a Superconducting Magnet at Room Temperature

multipole, vacuum, wiggler, superconducting-magnet

4281

J.C. Jan, C.-C. Chang, Y.L. Chu, J.C. Huang, C.-S. Hwang, C.Y. Kuo, F.-Y. Lin
NSRRC, Hsinchu, Taiwan

A superconducting multipole wiggler (SMPW) was fabricated at the National Synchrotron Radiation Research Center (NSRRC) and was installed in the Synchrotron Light Research Institute (SLRI). A 3.5 T field strength could be generated by the NbTi coils and the magnetic arrays are immersed in a liquid helium (LHe) bath. A removable mapping chamber, made from thin stainless steel sheets, was developed to allow field mapping in the narrow aperture of the SMPW. The mapping chamber provides a room temperature environment for the magnetic field mapping and enables an easier field scan in the cryostat. The design for the mapping chamber includes a blockage of heat transfer from room temperature to the LHe bath and is strong enough to resist deformations during evacuation. The mechanical design, strain simulation, thermal simulation, dummy test and measurement results with the mapping chamber will be discussed in this paper.

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reference for this paper ※ https://doi.org/10.18429/JACoW-IPAC2019-THPTS072

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paper received ※ 10 April 2019 paper accepted ※ 23 May 2019 issue date ※ 21 June 2019

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THPTS076

Design and Construction of Sextupole Magnet Prototype for Siam Photon Source II Project

sextupole, quadrupole, software, multipole

4295

S. Prawanta, B. Boonwanna, P. Klysubun, A. Kwankasem, S. Pongampai, V. Sooksrimuang, P. Sudmuang, P. Sunwong
SLRI, Nakhon Ratchasima, Thailand

Siam Photon Source II (SPS-II) project in Thailand is the third-generation synchrotron light source. The lattice of the 3 GeV electron storage ring has been designed, consisting of 14 Double Triple Bend Achromat (DTBA) cells with the total circumference of 321.3 m. The storage ring lattice includes 56 bending magnets, 28 combined dipole and quadrupole magnets, 224 quadrupole magnets and 84 multifunction sextupole magnets. This paper presents the design and construction of a sextupole magnet prototype for SPS-II project. Magnet prototype was designed with the magnetic field gradient of 2,030 T/m2 and includes functions of skew-quadrupole, horizontal and vertical correctors. The magnetic core is made of S10C low-carbon steel. A prototype of sextupole magnet has been constructed. All dimensional tolerances are within the range of ±20 µm.

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reference for this paper ※ https://doi.org/10.18429/JACoW-IPAC2019-THPTS076

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paper received ※ 15 May 2019 paper accepted ※ 23 May 2019 issue date ※ 21 June 2019

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