IPAC2019 - List of Keywords (GUI)

Paper	Title	Other Keywords	Page
MOPGW002	Longitudinal Kicker Design for Sirius Light Source	cavity, kicker, HOM, feedback	57
	H.O.C. Duarte, A. Barros LNLS, Campinas, Brazil
	An overloaded cavity kicker for the Sirius longitudinal bunch-by-bunch feedback system will be presented in this contribution. 4th generation light sources’ lower aperture of vacuum chambers lead to higher cutoff frequencies, jeopardizing the electromagnetic performance of cavities by trapping higher order modes (HOMs) inside the structure. With the objective of damping longitudinal and transverse HOMs without compromising the kicker shunt impedance, solutions as cavity radius reduction, tapered transitions and other geometry changes are discussed herein.
DOI •	reference for this paper ※ https://doi.org/10.18429/JACoW-IPAC2019-MOPGW002
About •	paper received ※ 15 May 2019 paper accepted ※ 17 May 2019 issue date ※ 21 June 2019
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MOPGW004	Microphonics Suppression in ARIEL ACM1 Cryomodule	cavity, cryomodule, linac, pick-up	65
	Y. Ma, K. Fong, J.J. Keir, D. Kishi, S.R. Koscielniak, D. Lang, R.E. Laxdal, R.S. Sekhon TRIUMF, Vancouver, Canada
	Now the stage of the 30MeV portion of ARIEL (The Advanced Rare Isotope Laboratory) e-Linac is under commissioning which includes an injector cryomodule (ICM) and the 1st accelerator cryomodule (ACM1) with two cavities configuration. The two ACM1 cavities are driven by a single klystron with vector-sum control and running in CW mode. During the commissioning, the ACM1 cavities gradient and stability was limited by ponderomotive effect. Acoustic noise from the environment vibration generated by cooling water system, cryogenic system and vacuum system have been identified to certain external source and some damping has been installed. In this paper, the progress of the microphonics suppression of ACM1 is presented.
DOI •	reference for this paper ※ https://doi.org/10.18429/JACoW-IPAC2019-MOPGW004
About •	paper received ※ 01 May 2019 paper accepted ※ 23 May 2019 issue date ※ 21 June 2019
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MOPGW047	Analysis and Simulation of the "After-Pulse" RF Breakdown	cavity, simulation, timing, 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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MOPGW061	Radiation from a Dielectrically Loaded Waveguide with Open End	vacuum, radiation, embedded, acceleration	228
	S.N. Galyamin, A.A. Grigoreva, A.V. Tyukhtin, V.V. Vorobev Saint Petersburg State University, Saint Petersburg, Russia A. Aryshev KEK, Ibaraki, Japan
	Funding: Work supported by Russian Science Foundation (Grant No. 18-72-10137). Open-ended waveguide structures with dielectric loading excited by specially prepared electron bunches are considered as promising candidates for development of contemporary sources of Terahertz (THz) radiation. Despite of the fact that both ordinary vacuum THz devices (e.g., backward wave oscillator) are widely available and other mechanisms for THz generation are discussed, beam driven sources are still extremely attractive due to the extraordinary peak power of THz radiation. In this report, we study electromagnetic (EM) field produced by a charged particle bunch exiting an open-ended circular waveguide with dielectric filling placed inside collinear vacuum waveguide of a larger radius. Based on the previously developed theory, we mainly investigate Cherenkov radiation generated penetrated vacuum regions of the structure due to the diffraction mechanism. We pay attention to the case of a train of short bunches resulting in high-order Cherenkov modes excitation. We also develop analytical procedure allowing performing the limiting process to the case of infinite radius of the outer waveguide. B.D. O’Shea et al., Nature Communications, Vol. 7, P. 12763, (2016). ** S.N. Galyamin et al., J. Instrumentation, Vol. 13, P. C02012 (2018).
DOI •	reference for this paper ※ https://doi.org/10.18429/JACoW-IPAC2019-MOPGW061
About •	paper received ※ 15 May 2019 paper accepted ※ 20 May 2019 issue date ※ 21 June 2019
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MOPGW064	On Wakefield in Dielectric Waveguide with Shallow Corrugation of Metallic Wall	radiation, ECR, wakefield, impedance	237
	A.V. Tyukhtin, E.R. Akhmatova, T.Yu. Alekhina, 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). Bunch radiation in periodical waveguides was mainly analyzed for situations when wavelengths are comparable to the structure period (Smith-Purcell emission). However, it is also of interest to study the "long-wave radiation" with wavelengths which are much larger than the structure period,. In such situation, the exact boundary conditions on the complicated periodic surface can be replaced with the equivalent boundary conditions (EBC) which must be fulfilled on the smooth surface. Earlier we considered with this approach radiation of the bunch moving along the axis of circular vacuum corrugated waveguide. Comparison of analytical results with COMSOL simulations showed high accuracy of the EBC method. Here we analyze an analogous problem for the waveguide with corrugated wall and dielectric filling under condition that Cherenkov effect takes place in the dielectric. Due to this fact the radiation differs radically from that in the vacuum waveguide. At the same time, the radiation has essential differences from the one in the usual dielectric waveguide. The radiation properties in the waveguide under consideration and its differences from the radiation in the waveguide with smooth wall are analyzed. G. Stupakov, K. Bane, Phys. Rev. ST-AB, 15 (2012) 124401. ** A.V. Tyukhtin et al, J. of Instrumentation, 13 (2018) C04009.
DOI •	reference for this paper ※ https://doi.org/10.18429/JACoW-IPAC2019-MOPGW064
About •	paper received ※ 15 May 2019 paper accepted ※ 20 May 2019 issue date ※ 21 June 2019
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MOPGW067	On Coordinate Systems in Beam Dynamics	simulation, 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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MOPGW114	Bayesian Approach for Linear Optics Correction	quadrupole, optics, lattice, distributed	390
	Y. Li, W.X. Cheng, R.S. Rainer BNL, Upton, Long Island, New York, USA
	With a Bayesian approach, the linear optics correction algorithm for storage rings is revisited. In modern ring-based accelerators, optics corrections are determined from repetitive measurements which help identify systematic and random quadrupole errors in presence of various measurement noises. This process is a multivariate nonlinear regression problem driven by either a completed lattice model or a Jacobian matrix. Starting from the Bayes’ theorem, ’likelihood functions’ and ’prior probability’ distributions are extracted from a complete linear optics model. Under some assumptions, the least square algorithm and then the Jacobian matrix approach can be re-derived. The coherence of the correction algorithm is ensured through specifying a self-consistent regularization coefficient to prevent overfitting. Optimal weights for different correction objectives are obtained based on their measurement noise level. A new technique has been developed to resolve degenerated quadrupole errors when observed at a few select BPMs. A necessary condition of being distinguishable is that their optics response vectors seen at these specific BPMs should be near-orthogonal.
DOI •	reference for this paper ※ https://doi.org/10.18429/JACoW-IPAC2019-MOPGW114
About •	paper received ※ 18 April 2019 paper accepted ※ 20 May 2019 issue date ※ 21 June 2019
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MOPRB022	Current Status of the High-Power RF Systems During Phase2 Operation in SuperKEKB	klystron, cavity, operation, status	619
	K. Watanabe, K. Marutsuka, Ma. Yoshida, S.I. Yoshimoto KEK, Ibaraki, Japan
	The SuperKEKB is an asymmetric-energy two-ring collider consisting of the high-energy ring (HER) for 7 GeV electrons and the low-energy ring (LER) for 4 GeV positrons at KEK. Both the electron and positron beams are injected from the Linac injector complex, which includes a newly constructed 1.1 GeV positron damping ring (DR) to supply a high-quality low emittance positron beam to the LER. The high power RF system has a role to drive the ARES cavities and the superconducting RF cavities for the SuperKEKB. The operating frequency of RF system is 508.9 MHz. The required RF power from the klystron at maximum storage beam current is ~850 kW (CW). The number of RF stations is total 31 for the main ring (MR) and DR. The status of each high power RF components, troubles of them and operation condition that occurred during phase 2 commissioning from Feb 2018 to July 2018 will be reported in this paper.
DOI •	reference for this paper ※ https://doi.org/10.18429/JACoW-IPAC2019-MOPRB022
About •	paper received ※ 15 May 2019 paper accepted ※ 20 May 2019 issue date ※ 21 June 2019
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MOPRB056	THz Radiator Based on Photonic Band Gap Crystal for SwissFEL	electron, photon, experiment, FEL	693
	L. Shi, R. Ischebeck, S. Reiche PSI, Villigen PSI, Switzerland
	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 701647. The electromagnetic radiation in 1-20 THz has many unique properties when it interacts with matter due to its non-ionizing excitation in matter. Especially the dynamics of the excited matter can be probed with the help of X-ray pulses at a free electron laser facility, e.g. SwissFEL, to deepen our understanding of a wide range of phenomena. Due to its high research potential, various means of THz generation have been proposed and demonstrated. We investigate preliminarily here its generation based on a relativistic electron bunch and a photonic band gap crystal (PBG) made of dielectric rods. The PBG provides additional degrees of freedom for the THz pulse tuning. Additionally, the unwanted radiation parts can be damped by the structure in order to minimize the deleterious beam dynamics effects. The crystal also promises the integration of generation, filtering and coupling for transport into a single piece.
DOI •	reference for this paper ※ https://doi.org/10.18429/JACoW-IPAC2019-MOPRB056
About •	paper received ※ 14 May 2019 paper accepted ※ 23 May 2019 issue date ※ 21 June 2019
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MOPRB067	High-gradient Single Cycle Terahertz Accelerating Structures	gun, acceleration, cathode, electron	731
	S.P. Antipov, E. Gomez, S.V. Kuzikov Euclid TechLabs, LLC, Solon, Ohio, USA A.A. Vikharev IAP/RAS, Nizhny Novgorod, Russia
	Recently, gradients on the order of 1 GV/m level have been obtained in a form of single cycle (~1 ps) THz pulses produced by conversion of a high peak power laser radiation in nonlinear crystals (~1 mJ, 1 ps, up to 3% conversion efficiency). These pulses however are broadband (0.1-5 THz) and therefore a new accelerating structure type is required. For electron beam acceleration with such pulses we propose arrays of parabolic focusing micro-mirrors with common central. These novel structures could be produced by a femtosecond laser ablation system developed at Euclid Techlabs. This technology had already been tested for production of several millimeters long, multi-cell structure which has been testing with electron beam. We also propose using of structures where necessary GV/m E-fields are excited by a drive bunch travelling in the corrugated waveguide. The radiated by drive bunch sequence of short range delayed wakes are guided in this case by metallic disks and reflected back being focused exactly at time when the witness bunch arrives.
DOI •	reference for this paper ※ https://doi.org/10.18429/JACoW-IPAC2019-MOPRB067
About •	paper received ※ 21 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	lattice, simulation, 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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MOPTS050	VSWR Adjustment for ACS Cavity in J-PARC LINAC	cavity, coupling, simulation, 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.
DOI •	reference for this paper ※ https://doi.org/10.18429/JACoW-IPAC2019-MOPTS050
About •	paper received ※ 01 May 2019 paper accepted ※ 18 May 2019 issue date ※ 21 June 2019
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TUXXPLM2	SRF Cavity Fault Classification Using Machine Learning at CEBAF	cavity, cryomodule, SRF, operation	1167
	A.D. Solopova, A. Carpenter, T. Powers, Y. Roblin, C. Tennant JLab, Newport News, Virginia, USA K.M. Iftekharuddin, L. Vidyaratne ODU, Norfolk, Virginia, USA
	The Continuous Electron Beam Accelerator Facility (CEBAF) at Jefferson Lab is the first large high power CW recirculating electron accelerator which makes use of SRF accelerating structures configured in two antiparallel linacs. Each linac consists of twenty C20/C50 cryomodules each containing eight 5-cell cavities and five C100 upgrade cryomodules each containing eight 7-cell cavities. Accurately classifying the source of cavity faults is critical for improving accelerator performance. In addition to archived signals sampled at 10 Hz, a cavity fault triggers a waveform acquisition process where 16 waveform records sampled at 5 kHz are recorded for each of the 8 cavities in the effected cryomodule. The waveform record length is sufficiently long for transient microphonic effects to be observable. Significant time is required by a subject matter expert to analyze and identify the intra-cavity signatures of imminent faults. This paper describes a path forward that utilizes machine learning for automatic fault classification. Post-training identification of the physical origins of faults are discussed, as are potential machine-trained model-free implementations of trip avoidance procedures. These methods should provide new insights into cavity fault mechanisms and facilitate intelligent optimization of cryomodule performance
	Slides TUXXPLM2 [4.404 MB]
DOI •	reference for this paper ※ https://doi.org/10.18429/JACoW-IPAC2019-TUXXPLM2
About •	paper received ※ 14 May 2019 paper accepted ※ 23 May 2019 issue date ※ 21 June 2019
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TUPMP051	MULTIPACTOR SUPPRESSION BY LASER ABLATION SURFACE ENGINEERING FOR SPACE APPLICATIONS	electron, laser, multipactoring, controls	1365
	R. Valizadeh, A.N. Hannah, O.B. Malyshev, B.S. Sian STFC/DL/ASTeC, Daresbury, Warrington, Cheshire, United Kingdom J.S. Colligon University of Huddersfield, Huddersfield, United Kingdom Y. Dan Hitachi High-Technologies Corp., Ibaraki-ken, Japan V.R. Dhanak The University of Liverpool, Liverpool, United Kingdom J. Mutch STFC/DL, Daresbury, Warrington, Cheshire, United Kingdom B.S. Sian UMAN, Manchester, United Kingdom N. Sykes Micronanics Laser Solution Center, Didcot, United Kingdom
	Developing a surface with low Secondary Electron Yield (SEY) is one of the main ways of mitigating electron cloud and beam-induced electron multipacting in high-energy charged particle accelerators and space-borne RF equipment for communication purposes. In this study we report on the secondary electron yield (SEY) measured from silver coated aluminium alloy as-received and after laser ablation surface engineering (LASE). Analysis shows the SEY can be reduced by 43% using LASE. EDX and SEM analysis shows it is possible to reduce the SEY whilst maintaining the original surface composition.
DOI •	reference for this paper ※ https://doi.org/10.18429/JACoW-IPAC2019-TUPMP051
About •	paper received ※ 14 May 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, simulation, 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.
DOI •	reference for this paper ※ https://doi.org/10.18429/JACoW-IPAC2019-TUPGW019
About •	paper received ※ 22 May 2019 paper accepted ※ 23 May 2019 issue date ※ 21 June 2019
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TUPGW098	Fabrication & Cold Tests of a Millimeter-Period RF Undulator	undulator, laser, FEL, electron	1643
	F. Toufexis, B.J. Angier, D. Gamzina, S.G. Tantawi SLAC, Menlo Park, California, USA
	Funding: This project was funded by U.S. Department of Energy under Contract No. DE-AC02-76SF00515, and the National Science Foundation under Contract No. PHY-1415437. To reduce the linac energy required for an FEL radiating at a given wavelength, and hence its size, a smaller undulator period with sufficient field strength is needed. Previous work from our group successfully demonstrated a microwave undulator at 11.424GHz, using a corrugated cylindrical waveguide operating at the HE11 modes. We have designed a mm-wave undulator cavity at 91.392GHz* with an equivalent undulator period of 1.75 mm. This undulator requires 1.4 MW for sub microsecond pulses for an equivalent K value of 0.1. In this work we present the mechanical design and fabrication of this 91.392 GHz RF Undulator, as well as preliminary cold test data. * F. Toufexis and S.G. Tantawi, "A 1.75-mm Period RF-Driven Undulator", Proceedings of IPAC17.
DOI •	reference for this paper ※ https://doi.org/10.18429/JACoW-IPAC2019-TUPGW098
About •	paper received ※ 10 May 2019 paper accepted ※ 22 May 2019 issue date ※ 21 June 2019
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TUPGW099	Superconducting Crab Cavity Options for Short X-Ray Pulse Generation in SPEAR3	cavity, sextupole, impedance, HOM	1647
	F. Toufexis, V.A. Dolgashev, X. Huang, Z. Li SLAC, Menlo Park, California, USA
	Funding: This project was funded by U.S. Department of Energy under Contract No. DE-AC02-76SF00515. We are exploring methods to generate short X-ray pulses in SPEAR3 on the order of 1 ps to enable studying ultrafast processes in materials. We are developing a 2-frequency crab cavity scheme with two sets of crab cavities* at the 6th and 6.5th harmonics of the 476 MHz ring RF frequency. In previous work we studied a normal conducting crab cavity for SPEAR3. In this work we explored two superconducting cavity options: a traditional elliptical cavity and the Quasi-waveguide Resonator. We found that the Quasi-waveguide Resonator cannot meet our field uniformity specifications due to higher order multipole fields. We then optimized a traditional elliptical cavity with the input, Lower Order Modes, and Higher Order Modes couplers following the Argonne Advanced Photon Source design. A. Zholents, et al, Nucl. Instrum. Methods Phys. Res., Sect. A, Vol. 425 (1999), p. 385. Z. Li, et al, Proceedings of IPAC17. * A. Lunin, et al, Proceedings of HOMSC14.
DOI •	reference for this paper ※ https://doi.org/10.18429/JACoW-IPAC2019-TUPGW099
About •	paper received ※ 11 May 2019 paper accepted ※ 21 May 2019 issue date ※ 21 June 2019
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TUPGW108	Characterization of NEG Coatings for SLS 2.0	impedance, resonance, coupling, vacuum	1662
	M.M. Dehler, A. Citterio PSI, Villigen PSI, Switzerland S. Alberti, J.P. Hogge SPC-EPFL, Lausanne, Switzerland M. Hahn, H.P. Marques ESRF, Grenoble, France X.Y. Liu USTC/NSRL, Hefei, Anhui, People’s Republic of China
	To limit desorption and ameliorate pumping of the narrow 20 mm aperture vacuum chamber of SLS2.0, it is planned to fully coat it with nonevaporable getter (NEG) material. NEG coating can be produced with different structural characteristics, from dense films to columnar growth, with corresponding distinct electrical properties affecting the machine impedance and the instability threshold of the accelerator. In order to evaluate and characterize the coating process for geometries similar to the SLS chamber, we measured the resonance properties of coated and uncoated shorted waveguide pieces. First tests were done with standard X band waveguides at 12 and 7 GHz. Test setups using elliptical cross sections are in preparation, also for higher frequencies allowing the characterization of thin NEG layers. The final goal is to have a standardized process to test of samples coated by external producers. We describe the setups and first results.
DOI •	reference for this paper ※ https://doi.org/10.18429/JACoW-IPAC2019-TUPGW108
About •	paper received ※ 10 May 2019 paper accepted ※ 22 May 2019 issue date ※ 21 June 2019
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TUPRB002	The Conceptual Design of a 36 GHz RF Undulator	undulator, cavity, electron, photon	1676
	D. Zhu ASCo, Clayton, Victoria, Australia A.W. Cross, L. Zhang USTRAT/SUPA, Glasgow, United Kingdom Y.E. Tan AS - ANSTO, Clayton, Australia
	The CompactLight project supported by European H₂020 is to design a hard X-ray FEL facility beyond today’s state of the art. The project integrates photo injector, X-band acceleration and innovative compact short-period undulators together to make the machine more compact. RF undulator has an extraordinary advantage of working at very short undulator period. A conceptual design for a RF undulator at 36 GHz using a corrugated cylindrical waveguide operating in the HE11 mode is presented in this paper. Based on beam dynamics simulation and photon beam radiation simulations, the possibility of RF undulator to be used in CompactLight project is evaluated.
DOI •	reference for this paper ※ https://doi.org/10.18429/JACoW-IPAC2019-TUPRB002
About •	paper received ※ 15 May 2019 paper accepted ※ 23 May 2019 issue date ※ 21 June 2019
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TUPRB015	Cryogenic, in-Vacuum Magnetic Measurement Setup for Superconducting Undulators	vacuum, undulator, detector, synchrotron	1709
	A.W. Grau, S. Casalbuoni, N. Glamann, D. Saez de Jauregui KIT, Eggenstein-Leopoldshafen, Germany
	The magnetic field quality has a strong impact on the performance of insertion devices (IDs) when installed in synchrotron light sources. Superconducting IDs have the advantage to produce a higher magnetic peak field for a given gap and period length than IDs assembled with permanent magnets. Before installation of a superconducting ID in a synchrotron light source it is of fundamental importance to characterize the magnetic properties by accurate field and field integral measurements. We follow this aim within our R&D program for superconducting undulators (SCUs). In this contribution, we describe the equipment and the challenges of a cryogenic, in vacuum measurement setup to perform magnetic measurements of the local field, the field integrals and the multipole components of in vacuum SCUs assembled in the final cryostat.
DOI •	reference for this paper ※ https://doi.org/10.18429/JACoW-IPAC2019-TUPRB015
About •	paper received ※ 29 April 2019 paper accepted ※ 23 May 2019 issue date ※ 21 June 2019
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TUPRB045	Stimulated Excitation by Seeding With Cherenkov Radiation in an Optical Cavity	radiation, cavity, electron, ion-source	1785
	S.M. Jiang, Z.G. He, Q.K. Jia, W.W. Li, L. Wang USTC/NSRL, Hefei, Anhui, People’s Republic of China D. He Anhui Electrical Engineering Professional Technique College, Hefei, People’s Republic of China
	Funding: Work supported by National Foundation of Natural Sciences of China (11775216, 11705198, 11675178), and Fundamental Research Funds for the Central Universities (WK2310000061). By seeding with narrow-band Cherenkov radiation from a dielectric loaded waveguide(DLW), stimulated excitation in an optical cavity is presented. The evolution and energy loss of the field oscillating in optical cavity is analysed by the theoretical and numerical calculation. The results show that the high order TM modes of the Cherenkov radiation can be better preserved after a large number of roundtrips in the optical cavity and this scheme offers a potential method of realizing high power Terahertz radiation source in a compact facility.
DOI •	reference for this paper ※ https://doi.org/10.18429/JACoW-IPAC2019-TUPRB045
About •	paper received ※ 30 April 2019 paper accepted ※ 18 May 2019 issue date ※ 21 June 2019
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TUPRB050	The Optical Resonator of CTFEL for Range of 1 to 2 THz	FEL, radiation, electron, coupling	1795
	X.J. Shu, Y.H. Dou Institute of Applied Physics and Computational Mathematics, People’s Republic of China
	A high power THz free electron laser (FEL) facility is under construction at China Academy of Engineering Physics (CTFEL). The radiation frequency of the FEL facility will be tuned in range of 1~3 THz and the average output power is about 10 W. The system mainly consists of a GaAs photoemission DC gun, superconductor accelerator, hybrid wiggler, optical cavity. The first lasing is obtained on Aug. 29, 2017, and CTFEL is operated in range of 2-4THz, but cannot lasing at the frequency below 1.8 THz. The optical resonator of CTFEL must be optimized to ensure lasing in range of 1 to 2 THz.. The lasing strongly depends on the performance of the optical resonator including output efficiency, gain and round-trip loss. The optical resonator consists of metal-coated reflect mirror, the centre-hole output mirror, waveguide. The influence of waveguide on the quality of optical cavity is evaluated by the 3D OSIFEL code. The waveguide size and output hole radius is optimized to different frequencies between 1 THz to 2 THz.
DOI •	reference for this paper ※ https://doi.org/10.18429/JACoW-IPAC2019-TUPRB050
About •	paper received ※ 13 May 2019 paper accepted ※ 24 May 2019 issue date ※ 21 June 2019
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TUPRB094	New Superconducting Undulator Magnetic Measurement System for the Advanced Photon Source Upgrade	undulator, photon, vacuum, storage-ring	1881
	M. Kasa, E.R. Anliker, Y. Ivanyushenkov, Y. Shiroyanagi ANL, Argonne, Illinois, USA
	Funding: Work supported by the U.S. Department of Energy, Office of Science, under Contract No. DE-AC02-06CH11357. Magnetic measurements of existing superconducting undulators (SCUs) are performed under normal operating conditions after final assembly into the cryostat and before installation on the Advanced Photon Source (APS) storage ring. The SCU cryostat for the APS upgrade has been scaled in length from the current cryostat and will contain two SCUs. While some aspects of the current measurement system are desirable to retain, such as a room temperature measurement bore, scaling the current measurement techniques to the length required for the APS upgrade cryostat is not feasible. To address these challenges a unique system has been developed at the APS to allow measurements of the two SCU magnets in the long cryostat. The measurement system developed allows the magnets to be operated under normal operating conditions while maintaining the measurement equipment at room temperature and atmospheric pressure.
DOI •	reference for this paper ※ https://doi.org/10.18429/JACoW-IPAC2019-TUPRB094
About •	paper received ※ 14 May 2019 paper accepted ※ 22 May 2019 issue date ※ 21 June 2019
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TUPTS065	RF Conditioning of the CLARA 400 Hz Photoinjector	cavity, controls, vacuum, operation	2067
	L.S. Cowie, D.J. Scott STFC/DL/ASTeC, Daresbury, Warrington, Cheshire, United Kingdom
	Automated conditioning of the 400 Hz photoinjector for CLARA was begun and the conditioning program refined. The conditioning was performed at 100 Hz. Masks were used to detect breakdowns in the reflected power and phase, and the breakdown rate was limited to 5x106 breakdowns per pulse. The cavity gradient and breakdown rate evolution over the conditioning time is presented. Post-pulse multipactor and other evidence of electron effects were detected. Possible mechanisms for this are discussed. The conditioning was interrupted by breakdown in the waveguide after reaching 2.5 MW, and will be resumed after the planned 6 month shutdown of CLARA.
DOI •	reference for this paper ※ https://doi.org/10.18429/JACoW-IPAC2019-TUPTS065
About •	paper received ※ 14 May 2019 paper accepted ※ 21 May 2019 issue date ※ 21 June 2019
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WEPMP044	Mu2e Electrostatic Septa Volumetric Exchange of Fc-40 Dielectric in High Radiation Environments	radiation, septum, cathode, extraction	2434
	M.L. Alvarez, A. Deshpande, K.R. Hunden, V.P. Nagaslaev, E. Pirtle Fermilab, Batavia, Illinois, USA
	Funding: * Operated by FRA, LLC under Contract No. DEAC02-07CH11359 and Grant Award No. LAB 18-1802 with the United States Department of Energy. Two electrostatic septa (ESS) are being designed for the slow extraction of 8 GeV proton beam for the Mu2e experiment at Fermilab. Special attention is given to the high voltage feedthrough (HVF), which energizes the cathode creating the bending field. The FC-40 dielectric fluid, surrounding the HV cable breaks down from radiation exposure, which reduces its insulating capabilities. The new HVF design focuses on effective replacement of the exposed fluid and eliminating the stagnant areas of low exchange rate. A preliminary test using a fully transparent prototype HVF and water was conducted to understand the volumetric exchange rate of the high radiation region. Here we discuss the results of these tests and further studies using the FC-40. malvare4@fnal.gov * vnagasl@fnal.gov
DOI •	reference for this paper ※ https://doi.org/10.18429/JACoW-IPAC2019-WEPMP044
About •	paper received ※ 14 May 2019 paper accepted ※ 23 May 2019 issue date ※ 21 June 2019
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WEPGW003	High-Level Applications for the Sirius Accelerator Control System	EPICS, controls, MMI, linac	2462
	X.R. Resende, L. Liu, A.C.S. Oliveira, F.H. de Sá, G.L. do Prado LNLS, Campinas, Brazil
	Sirius is the new 3 GeV low-emittance Brazilian Synchrotron Light source under installation and commissioning at LNLS. The machine control system is based on EPICS and when the installation is complete it should have a few hundred thousand process variables in use. For flexible integration and intuitive control of such sizable system a considerable number of high-level applications, input/output controllers and graphical user interfaces have been developed, mostly in Python, using a variety of libraries, such as PyEpics, PCASPy and PyDM. Common support service applications (Archiver Appliance, Olog, Apache server, a mongoDB-based configuration server, etc) are used. Matlab Middle Layer is also an available option to control EPICS applications. Currently system integration tests are being performed concomitant with initial phases of accelerator commissioning and installation. A set of functionalities is already available: Linac’s control; timing subsystem control; machine snapshots; optics measurements and correction; magnets settings and cycling; Booster orbit acquisition and correction, and so on. From the experience so far, subsystems communications have worked satisfactorily but there has been a few unexpected component performance. In this paper we discuss this experience and descrive the libraries and packages used in high-level control system , as well as the difficulties faced to implement and to operate them.
DOI •	reference for this paper ※ https://doi.org/10.18429/JACoW-IPAC2019-WEPGW003
About •	paper received ※ 15 May 2019 paper accepted ※ 21 May 2019 issue date ※ 21 June 2019
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WEPGW045	Application of Clustering by Fast Search and Find of Density Peaks to Beam Diagnostics at SSRF	SRF, storage-ring, diagnostics, electron	2581
	R. Jiang, Y.B. Leng SSRF, Shanghai, People’s Republic of China
	With the increased technological complexity of accelera-tors, meeting the demand of beam diagnostics and opera-tion need more powerful and faster methods. And detect-ing the accuracy and stability of beam position moni-tors(BPMs) are important for all kinds of measurement systems and feedback systems in particle accelerator field. As an effective tool for data analysis and automa-tion, the machine learning methods had been used in accelerator physics field, recently. Among machine learn-ing methods, the clustering by fast search and find of density peaks as a typical unsupervised learning algo-rithms could be performed directly without training in arbitrary accelerator systems and could discover un-known patterns in the data. This paper used clustering by fast search and find of density peaks to detect faulty beam position monitor or monitoring beam orbit stability by analysis five typical parameters, that is beta oscilla-tion of X and Y direction(BetaX and BetaY), transverse oscillation of X and Y direction(AmpX and AmpY) and energy oscillation(AmpE). The results showed that cluster-ing by fast search and find of density peaks could classi-fy beam data into different clusters on the basis of their similarity. And that, aberrant run data points could be detected by decision graph. Morever, analysis results demonstrate the characteristic parameters AmpE, AmpX and BetaX amplitude have the same effect to distinguish the faulty BPMs and the AmpY and the BetaY amplitude are also.
DOI •	reference for this paper ※ https://doi.org/10.18429/JACoW-IPAC2019-WEPGW045
About •	paper received ※ 15 May 2019 paper accepted ※ 21 May 2019 issue date ※ 21 June 2019
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WEPGW074	MYRRHA DAQ Development	controls, EPICS, LabView, software	2645
	R. Modic Cosy lab, Ljubljana, Slovenia P. Della Faille, D. Vandeplassche SCK•CEN, Mol, Belgium P. Mekuc Cosylab, Ljubljana, Slovenia
	An approach to a generic Data Acquisition (DAQ) solution for the MYRRHA test stand at Louvain-la-Neuve (Belgium) will be described in this paper. Need for better sampling performance, signal quality, arbitrary processing and storage of measurements was a motivation for this work. A full integration of the DAQ system in the global EPICS control environment was a strong requirement. An intermediate DAQ platform was put in place to satisfy the control and experiment needs. The NI PXI platform is selected to minimize integration and development effort. NI LabVIEW is used to create a generic DAQ application. CALab library supported by BESSY is used to connect LabVIEW and EPICS. CSS GUI provides the user with the necessary control, visualization and configuration capability. The technical and organizational approach to the collaboration will be detailed in the paper. Necessary customizations of CSS and CALab and experience on using NI PXI for DAQ platform will be explained.
DOI •	reference for this paper ※ https://doi.org/10.18429/JACoW-IPAC2019-WEPGW074
About •	paper received ※ 14 May 2019 paper accepted ※ 21 May 2019 issue date ※ 21 June 2019
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WEPGW115	Radiation Robust RF Gas Beam Detector R&D for Intensity Frontier Experiments	detector, cavity, plasma, electron	2770
	K. Yonehara, A. Moretti Fermilab, Batavia, Illinois, USA M.A. Cummings, R.P. Johnson, G.M. Kazakevich Muons, Inc, Illinois, USA
	A novel radiation robust RF gas beam detector has been demonstrated by using the Main Injector beam at Fermilab. The detector demonstrated a stable signal gain, fast response time, and high radiation resistivity with intense proton beams. The plasma process in the detector is studied to validate the plasma physics model. The result suggests that the detector is applicable for Long Baseline Neutrino Facility at Fermilab. To prepare for the LBNF, a proto type detector will be made and applied for the Neutrino at Main Injector target system. Progress of the project will be given in the presentation.
DOI •	reference for this paper ※ https://doi.org/10.18429/JACoW-IPAC2019-WEPGW115
About •	paper received ※ 15 May 2019 paper accepted ※ 21 May 2019 issue date ※ 21 June 2019
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WEPGW116	LHC Optics Measurement and Correction Software Progress and Plans	optics, software, coupling, MMI	2773
	R. Tomás, F.S. Carlier, J.M. Coello de Portugal, J. Dilly, E. Fol, A. Garcia-Tabares, M. Hofer, E.H. Maclean, L. Malina, T.H.B. Persson, P.K. Skowroński, M.L. Spitznagel, A. Wegscheider, J. Wenninger CERN, Geneva, Switzerland J.F. Cardona, Y. Rodriguez UNAL, Bogota D.C, Colombia F.S. Carlier NIKHEF, Amsterdam, The Netherlands D. Esperante Pereira, J. Fuster, D. Gonzalez-Iglesias IFIC, Valencia, Spain R. Hoekstra KVI, Groningen, The Netherlands
	LHC Optics Measurements and Corrections (OMC) require efficient on-line software applications to acquire and analyze data and to compute the necessary corrections. During Run 2 various measurement and correction techniques have been merged to yield unprecedented optics quality, increasing the required number of steps to finalize the optics commissioning and the size of the software project. In turn, this calls for a higher level of automation, where machine learning techniques are being implemented. During the Long Shutdown 2 a large refactoring of the codes will be in place to improve performance, maintainability and extensibility. A description of the current status of the software and future plans is given.
DOI •	reference for this paper ※ https://doi.org/10.18429/JACoW-IPAC2019-WEPGW116
About •	paper received ※ 07 May 2019 paper accepted ※ 21 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	brightness, quadrupole, simulation, 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
DOI •	reference for this paper ※ https://doi.org/10.18429/JACoW-IPAC2019-WEPRB024
About •	paper received ※ 09 April 2019 paper accepted ※ 20 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, HOM, simulation	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.
DOI •	reference for this paper ※ https://doi.org/10.18429/JACoW-IPAC2019-WEPRB034
About •	paper received ※ 13 May 2019 paper accepted ※ 22 May 2019 issue date ※ 21 June 2019
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WEPRB039	Tuning of a Tapered Ridge-Loaded Waveguide Coupler for a Drift Tube LINAC of the Compact Pulsed Hadron Source	coupling, DTL, linac, target	2893
	Y. Lei, C.T. Du, X. Guan, R. Tang, X.W. Wang, Q.Z. Xing, S.X. Zheng TUB, Beijing, People’s Republic of China
	This paper presents the tuning result of a tapered ridge-loaded waveguide coupler for the drift tube linac (DTL) of the compact pulsed hadron source (CPHS) at Tsinghua University. The coupler has been designed, manufactured, and mounted on the DTL cavity for the cold measurement and tuning. The iris diameter of the coupler which is related to the coupling coefficient needs to be determined in the tuning experiment, due to the difference between the designed and measured quality factors. Meanwhile, we found that the relationship between the coupling coefficient and iris diameter from the traditional analytical design method is not applicable when the iris diameter is relatively large. In this paper, the target coupling coeffi-cient is analysed, and the limit of the original analytical design is presented. The measurement method is intro-duced to improve the measurement efficiency and the tuning process of the coupling coefficient to the target value is described. After several iterations, the coupling coefficient is tuned to 1.54 which is close to the desired value of 1.56.
DOI •	reference for this paper ※ https://doi.org/10.18429/JACoW-IPAC2019-WEPRB039
About •	paper received ※ 30 April 2019 paper accepted ※ 22 May 2019 issue date ※ 21 June 2019
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WEPRB042	High Power Test of the First C-band Spherical Pulse Compressor Prototype	cavity, FEL, electron, linac	2896
	Z.B. Li SINAP, Shanghai, People’s Republic of China W. Fang, Q. Gu, X.X. Huang, J.H. Tan, Z.T. Zhao SSRF, Shanghai, People’s Republic of China
	Funding: National Natural Science Foundation of China (No. 11675249) Recently, a new C-band (5712 MHz) compact spherical radio frequency (RF) pulse compressor was designed and tested for Shanghai Soft X-ray Free Electron Laser Facili-ty (SXFEL). This pulse compressor utilizes one high Q₀ spherical RF resonant cavity that works with two TE1, 1,3 modes and a dual-mode polarized coupler. The peak power multiply factor is 6.1 and average power gain 3.8 in theory. During the high power test, a peak power mul-tiply factor of 5.74 and average power gain of 3.77 was achieved. This paper presents the RF measurement of the C-band spherical pulse compressor and the high power test results.
DOI •	reference for this paper ※ https://doi.org/10.18429/JACoW-IPAC2019-WEPRB042
About •	paper received ※ 19 April 2019 paper accepted ※ 22 May 2019 issue date ※ 21 June 2019
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WEPRB043	Wakefield Suppression in the Main LINAC of the Klystron-Based First Stage of CLIC at 380 GeV	wakefield, HOM, damping, linac	2899
	J.Y. Liu, H.B. Chen, J. Shi, H. Zha TUB, Beijing, People’s Republic of China A. Grudiev CERN, Meyrin, Switzerland
	An alternative klystron-based scenario for the first stage of Compact Linear Collider (CLIC) at 380 GeV centre-of-mass energy was proposed. To preserve the beam stability and luminosity of CLIC, the beam-induced transverse long-range wakefield in main linac must be suppressed to an acceptable value. The design of klystron-based accelerating structure is based on waveguide damping structure (WDS). The high-order modes (HOMs) propagating into four waveguides are absorbed by HOM damping loads. In this paper, the wakefield suppression in CLIC-K based on GdfidL code simulations are presented.
DOI •	reference for this paper ※ https://doi.org/10.18429/JACoW-IPAC2019-WEPRB043
About •	paper received ※ 14 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	vacuum, simulation, 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.
DOI •	reference for this paper ※ https://doi.org/10.18429/JACoW-IPAC2019-WEPRB046
About •	paper received ※ 13 May 2019 paper accepted ※ 23 May 2019 issue date ※ 21 June 2019
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WEPRB047	High-Power Test of a 12 Cell Accelerating Structure Build in Halves	klystron, vacuum, shielding, ECR	2912
	M.M. Peng, Y.L. Jiang, J.Y. Liu, Z.N. Liu, X.C. Meng, J. Shi, H. Zha TUB, Beijing, People’s Republic of China
	An X-band 12 cell travelling-wave accelerating structure has been developed and high-power tested at Tsinghua University in China. This structure works at 2⁄3 π at the frequency of 11.424 GHz. It is a 12-cell constant-impedance structure build in halves and was silver-brazed as a vacuum tight structure. The high power test was conducted at Tsinghua X-band high power test facility [1] with a 50-MW X-band klystron at a repetition rate to 40 Hz. The final input power was 51.23 MW with a 200 ns pulse width, which means an accelerating gradient of 88.58 MV/m was reached. This paper presents the high power test results including the gradient and breakdown history.
DOI •	reference for this paper ※ https://doi.org/10.18429/JACoW-IPAC2019-WEPRB047
About •	paper received ※ 10 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	simulation, cavity, 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.
DOI •	reference for this paper ※ https://doi.org/10.18429/JACoW-IPAC2019-WEPRB048
About •	paper received ※ 14 May 2019 paper accepted ※ 21 May 2019 issue date ※ 21 June 2019
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WEPRB052	Design of Two Types of X-Band High Power Directional Coupler	coupling, simulation, 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.
DOI •	reference for this paper ※ https://doi.org/10.18429/JACoW-IPAC2019-WEPRB052
About •	paper received ※ 27 April 2019 paper accepted ※ 22 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, simulation, cavity	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.
DOI •	reference for this paper ※ https://doi.org/10.18429/JACoW-IPAC2019-WEPRB058
About •	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, HOM, simulation, 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.
DOI •	reference for this paper ※ https://doi.org/10.18429/JACoW-IPAC2019-WEPRB060
About •	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	simulation, klystron, 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.
DOI •	reference for this paper ※ https://doi.org/10.18429/JACoW-IPAC2019-WEPRB064
About •	paper received ※ 10 May 2019 paper accepted ※ 22 May 2019 issue date ※ 21 June 2019
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WEPTS037	DC Beam Space-Charge Modeling for OpenXAL	simulation, space-charge, LEBT, solenoid	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.
DOI •	reference for this paper ※ https://doi.org/10.18429/JACoW-IPAC2019-WEPTS037
About •	paper received ※ 14 May 2019 paper accepted ※ 20 May 2019 issue date ※ 21 June 2019
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WEPTS081	An Analytic Approach to Emittance Growth from the Beam-Beam Effect with Applications to the LHeC	proton, emittance, electron, collider	3307
	E.A. Nissen JLab, Newport News, Virginia, USA D. Schulte CERN, Meyrin, Switzerland
	Funding: Authored by Jefferson Science Associates, LLC under U.S. DOE Contract No. DE-AC05-06OR23177. The U.S. Government retains a non-exclusive, world-wide license to publish or reproduce this manuscript. In colliders with asymmetric rigidity such as the proposed Large Hadron electron Collider, jitter in the weaker beam can cause emittance growth via coherent beam-beam interactions. The LHeC in this case would collide 7 TeV protons on 60 GeV electrons, which can be modeled using a weak-strong model. In this work we estimate the proton beam emittance growth by separating out the longitudinal angular kicks from an off-center bunch interaction and produce an analytic expression for the emittance growth per turn in systems like the LHeC.
DOI •	reference for this paper ※ https://doi.org/10.18429/JACoW-IPAC2019-WEPTS081
About •	paper received ※ 01 May 2019 paper accepted ※ 22 May 2019 issue date ※ 21 June 2019
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THPMP044	Radiation Hard Sensor for Reactor Applications	laser, radiation, timing, detector	3545
	R.J. Abrams, M.A. Cummings, R.P. Johnson, T.J. Roberts Muons, Inc, Illinois, USA D.M. Kaplan Illinois Institute of Technology, Chicago, Illinois, USA
	A novel method of measuring temperature of the coolant inside a reactor core is presented. The method, which is both standoff and non-invasive, is based on the interaction between an ultrasonic pulse and a delayed light pulse in the coolant. In the interaction, the light pulse, which is scattered backward by Brillouin scattering, is frequency-shifted. The frequency shift is dependent on the temperature and other parameters of the coolant. The light pulses and the ultrasound pulses are generated and detected outside of the core.
DOI •	reference for this paper ※ https://doi.org/10.18429/JACoW-IPAC2019-THPMP044
About •	paper received ※ 14 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	simulation, 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
DOI •	reference for this paper ※ https://doi.org/10.18429/JACoW-IPAC2019-THPMP046
About •	paper received ※ 21 May 2019 paper accepted ※ 23 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, simulation	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.
DOI •	reference for this paper ※ https://doi.org/10.18429/JACoW-IPAC2019-THPMP050
About •	paper received ※ 14 May 2019 paper accepted ※ 22 May 2019 issue date ※ 21 June 2019
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THPGW033	Numerical Study of Photonic-Crystal-Based Dielectric Accelerators	photon, acceleration, electron, impedance	3653
	G. Torrisi, L. Celona, S. Gammino, D. Mascali, G. Sorbello INFN/LNS, Catania, Italy C. De Angelis, A. Locatelli University of Brescia, Brescia, Italy G.S. Mauro INFN/LNL, Legnaro (PD), Italy G. Sorbello University of Catania, Catania, Italy
	All-dielectric electromagnetic band gap (EBG) waveguides structures promise significant improvement of accelerating gradient of laser-driven acceleration with the potential to miniaturize the accelerator itself. In this work we study photonic crystal structures designed for acceleration of relativistic electrons. We explore the performance of the all-dielectric EBG accelerating waveguide structures thanks to full wave electromagnetic simulations of couplers and accelerating waveguides. The characteristic interaction impedance, accelerating gradient and all the key parameters that are typically used to characterize linear accelerators are evaluated and used to compare the properties of the accelerating mode field distribution in different geometries.
DOI •	reference for this paper ※ https://doi.org/10.18429/JACoW-IPAC2019-THPGW033
About •	paper received ※ 30 April 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, simulation, 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.
DOI •	reference for this paper ※ https://doi.org/10.18429/JACoW-IPAC2019-THPGW078
About •	paper received ※ 15 May 2019 paper accepted ※ 22 May 2019 issue date ※ 21 June 2019
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THPGW079	THz-Based Femtosecond MeV Electron Bunch Compression	electron, FEM, experiment, focusing	3766
	M.A.K. Othman, M.C. Hoffmann, M.E. Kozina, R.K. Li, E.A. Nanni, X. Shen, E.J. Snively, X.J. Wang SLAC, Menlo Park, California, USA
	Funding: This work was supported by Department of Energy contract DE-AC02-76SF00515. Probing structural dynamics at atomic spatial and ultrashort temporal scales reveals unprecedented details of fundamental behavior of nature, allowing for better understanding of intricate energy-matter interaction occurring at such scales. Developing state-of-the-art technology to access these details entails utilizing X-ray free-electron lasers (XFELs), ultrafast electron diffraction (UED), and advanced electron microscopes. In particular, ultrafast diffraction science received growing attention thanks to innovation in sources, detectors and instrumentation in general. Within this context, interest in laser-generated THz wave-matter interaction has recently emerged as a new regime for controlling electrons with high temporal precision. Previously, the SLAC UED team has demonstrated attosecond electron metrology using laser-generated single-cycle THz radiation, which is intrinsically phase locked to the optical drive pulses, to manipulate multi-MeV relativistic electron beams. Here we demonstrate further steps towards achieving ultrafast timing resolution that utilizes femtosecond electron bunches. The proposed setup allows for compressing electron beam bunches down to a femtosecond using interaction with high field single-cycle THz pulses. We demonstrate a novel design of a dispersion-free parallel-plate tapered waveguide that provides focusing of THz pulses achieving >100 MV/m field strength at the interaction point as measured by electro-optical sampling for ~7 μJ of incoming THz pulse energy. The structure is being designed and built for bunch compression experiments using the SLAC UED facility.
DOI •	reference for this paper ※ https://doi.org/10.18429/JACoW-IPAC2019-THPGW079
About •	paper received ※ 15 May 2019 paper accepted ※ 23 May 2019 issue date ※ 21 June 2019
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THPRB038	ALARM SYSTEM OF IRFEL AT NSRL	FEL, controls, interface, EPICS	3896
	X. Chen, C. Li, G. Liu, Z.X. Shao, Y. Song, J.G. Wang, K. Xuan USTC/NSRL, Hefei, Anhui, People’s Republic of China
	An InfraRed Free Electron Laser Light (IRFEL) is under commissioning at National Synchrotron Radiation Laboratory (NSRL). The control system of IRFEL is a distributed system based on Experimental Physics and Industrial Control System (EPICS). The alarm system is an essential part of the control system. It is developed based on the software Phoebus. The module named "Alarms" in Phoebus can store states and configuration information of the Process Variable (PV) in the Kafka topics. To meet our requirements, 3 kinds of alarm message distribution applications are developed, i.e. Web-Based GUI, WeChat and SMS. This paper will introduce the alarm system architecture and the implementations of the applications for alarm message distribution.
DOI •	reference for this paper ※ https://doi.org/10.18429/JACoW-IPAC2019-THPRB038
About •	paper received ※ 17 April 2019 paper accepted ※ 21 May 2019 issue date ※ 21 June 2019
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THPRB079	DC Testing and Phase Resolved Partial Discharge Measurements of the New Trigger Transformers for the LHC Beam Dump Kickers	high-voltage, operation, kicker, power-supply	3998
	T. Stadlbauer, A. Chmielinska, L. Ducimetière, D. Kontelis, T. Kramer, V. Senaj CERN, Geneva, Switzerland
	During LS2 the LHC beam dump kicker pulse generators will be subject to a substantial consolidation program. One major part is the replacement of the existing GTO stack trigger transformer by a new more performant one. The transformer is assembled, moulded and tested in-house. Part of the validation procedure are standard DC tests and subsequent discharge monitoring as well as newly introduced phase resolved partial discharge measurements. This paper briefly highlights the trigger transformer parameters and construction and outlines in detail the testing and partial discharge measurements. It concludes with a comparison and analysis of the results of the different measurement techniques.
DOI •	reference for this paper ※ https://doi.org/10.18429/JACoW-IPAC2019-THPRB079
About •	paper received ※ 14 May 2019 paper accepted ※ 23 May 2019 issue date ※ 21 June 2019
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THPRB086	Design & Optimization of the Alignment Supports for the New Laminated Magnets for the CERN East Area Consolidation Project	alignment, radiation, operation, secondary-beams	4020
	R. Vanhoutte, D. Brethoux, A. Ebn Rahmoun, S. Evrard, F.J. Harden, E. Harrouch, M. Lazzaroni, M. Lino Diogo dos Santos, R. Lopez, D.E. Nogtikov, J. Renedo Anglada CERN, Meyrin, Switzerland
	The East Area is one of CERNs experimental area, running since its foundation in 1958. Extracting a 24GeV proton beam from the Proton Synchrotron accelerator, the primary beam is divided into different secondary beams, serving various experiments and user’s facilities such as CLOUD, CHARM, IRRAD. Due to improved optics and an energy saving scheme, the facility will go under a renovation between 2019 and 2020, including the replacement of the magnets with new laminated ones to allow a cycled powering scheme. Those magnets need improved supports, and in some cases even a new design, to optimize the alignment operations in those areas. This article will mainly address the different proposed solutions for plug-in supports as well as for conventional ones.
DOI •	reference for this paper ※ https://doi.org/10.18429/JACoW-IPAC2019-THPRB086
About •	paper received ※ 15 May 2019 paper accepted ※ 23 May 2019 issue date ※ 21 June 2019
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THPRB112	Commission of the Transverse Bunch-by-Bunch Feedback at SPEAR3	feedback, kicker, injection, vacuum	4081
	K. Tian, W.J. Corbett, X. Huang, N. Kurita, D.J. Martin, J.A. Safranek, J.J. Sebek SLAC, Menlo Park, California, USA D. Teytelman Dimtel, San Jose, USA
	Funding: Work supported by US Department of Energy Contract DE-AC03-76SF00515. Driven by the demand of suppressing transverse beam instabilities and developing novel short pulse operation modes in SPEAR3 storage ring, a wide-band transverse bunch-by-bunch feedback system has been recently commissioned for SPEAR3 storage ring. The system was demonstrated to be sufficient to suppress the transverse coupled bunch instabilities caused by trapped RF modes in one of the in vacuum insertion devices. A new function of beam instability interlock has been developed and is part of machine protection system for the in vacuum insertion device. In addition, the bunch-by-bunch feedback system serves as a indispensable diagnostic tool that enables us to measure machine parameters, beam impedance, and characteristics of the beam instability modes. In this paper, we describe the scheme and performance of the bunch-by-bunch feedback system at SPEAR3.
DOI •	reference for this paper ※ https://doi.org/10.18429/JACoW-IPAC2019-THPRB112
About •	paper received ※ 14 May 2019 paper accepted ※ 23 May 2019 issue date ※ 21 June 2019
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THPRB116	Effect of Ground Motion Introduced by HL-LHC CE Work on LHC Beam Operation	ground-motion, luminosity, operation, civil-engineering	4092
	M. Schaumann, D. Gamba, M. Guinchard, L. Scislo, J. Wenninger CERN, Geneva, Switzerland
	Funding: Research supported by the HL-LHC project The official groundbreaking of the civil engineering (CE) work for the high luminosity upgrade of the LHC started on 15 June 2018 parallel to LHC beam operation. Compactor work and shaft excavation around the two low beta experiments, ATLAS and CMS, were expected to induce vibrations to the accelerator magnets and cause orbit disturbance, beam loss and potentially premature beam dumps. Ground motion sensors were installed on the surface and close to the triplets, where the CE works were expected to have the largest impact on the beams. This paper discusses the observations made on the LHC beams that could be correlated to CE work.
DOI •	reference for this paper ※ https://doi.org/10.18429/JACoW-IPAC2019-THPRB116
About •	paper received ※ 13 May 2019 paper accepted ※ 22 May 2019 issue date ※ 21 June 2019
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THPTS008	Prospects of Additive Manufacturing for Accelerators	cavity, vacuum, niobium, detector	4118
	N. Delerue, S. Jenzer LAL, Orsay, France H.C. Carduner SUBATECH, Nantes, France R.L. Gerard CERN, Meyrin, Switzerland P.M. Manil CEA-DRF-IRFU, France P.R. Repain LPNHE, Paris, France A. Simar UCL, Louvain-la-Neuve, Belgium
	Funding: Université Paris-SAclay, Labex P2IO and P2I departement Additive manufacturing allows the production of mechanical components often much faster than traditional manufacturing. Several accelerators components built using additive manufacturing have already been qualified for use in accelerator. A workshop was held in Orsay in December 2018 to discuss the prospects of using additive manufacturing for particle accelerators and particle detectors. We report here on the prospects as far as accelerators are concerned.
DOI •	reference for this paper ※ https://doi.org/10.18429/JACoW-IPAC2019-THPTS008
About •	paper received ※ 20 May 2019 paper accepted ※ 22 May 2019 issue date ※ 21 June 2019
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THPTS039	DESIGN OF A COMPACT VARIABLE X-BAND RF POWER SPLITTER	impedance, klystron, electron, network	4194
	F. Liu, H.B. Chen, J.Y. Liu, Z.N. Liu, J. Shi, H. Zha TUB, Beijing, People’s Republic of China
	This paper presents a design of a compact variable X-band RF power splitter. The RF power splitter includes one input port and two output ports, and the power divi-sion ratio can be adjusted by changing the position of a short circuit piston. This system keeps a good match (less than -40 dB) at any power division ratio. An E-bend waveguide structure is selected to make the geometry more compact (11cm in length, 3.5cm in width and 5 cm in height). Special studies was conducted to sustain a low surface electrical field (maximum 65 MV/m at 100 MW input), and large bandwidth (250MHz). This power split-ter is designed for high-power test stand at Tsinghua Uni-versity.
DOI •	reference for this paper ※ https://doi.org/10.18429/JACoW-IPAC2019-THPTS039
About •	paper received ※ 14 May 2019 paper accepted ※ 23 May 2019 issue date ※ 21 June 2019
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THPTS063	Development of a W-Band Power Extraction Structure	cavity, undulator, electron, extraction	4252
	F. Toufexis, B.J. Angier, D. Gamzina, A. McGuire, M. Shumail, S.G. Tantawi SLAC, Menlo Park, California, USA
	Funding: This project was funded by U.S. Department of Energy under Contract No. DE-AC02-76SF00515, and the National Science Foundation under Contract No. PHY-1415437. We are modifying the X-Band Test Accelerator at SLAC to operate as an Extreme Ultra Violet (EUV) light source. The existing photo electron gun will be replaced by a thermionic X-Band injector which utilizes RF bunch compression. The beam is accelerated up to 129 MeV using an X-Band traveling wave structure followed by a novel high shunt impedance standing wave structure. The beam then goes through a mm-wave undulator with a period of 1.75 mm, producing EUV radiation around 13.5 nm. The undulator is powered by a W-Band decelerator structure, which extracts the RF power from the electron beam. In this work we present the mechanical design and fabrication of the 91.392 GHz decelerator structure, as well as structural characterization of its cavities using SEM and 3D microscopy. F. Toufexis, et al, "A Compact EUV Light Source using a mm-wave Undulator", Proceedings of IPAC17.
DOI •	reference for this paper ※ https://doi.org/10.18429/JACoW-IPAC2019-THPTS063
About •	paper received ※ 10 May 2019 paper accepted ※ 22 May 2019 issue date ※ 21 June 2019
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THPTS087	Micro-aligned Solenoid for Magnetized Bunched-beam Electron Cooling of 100 GeV/u Ions	electron, solenoid, alignment, collider	4314
	P.M. McIntyre, J. Breitschopf, J. Gerity, J.N. Kellams Texas A&M University, College Station, USA J. Breitschopf, J. Gerity, J.N. Kellams, A. Sattarov ATC, College Station, Texas, USA
	Funding: This work is supported by grant DE-SC0018468 from the US Dept. of Energy. Magnetized electron cooling of ion beams requires pre-cise alignment of the electron beam with the equilibrium trajectory of the ion bunch. For the parameters required for JLEIC, a solenoid with bore field ~1 T, length ~30 m, and rms alignment of ~μrad is required. Such precise alignment has never been accomplished in a 1 T solenoid. The design of a micro-aligned solenoid is presented. A gap-separated stack of thin steel washers is located inside the solenoid. The washer stack shields transverse magnet-ic fields from its interior by a factor of ~10. A 30-washer module of the structure was built and measured using ultra-sensitive capacitive probes using a coordinate meas-uring machine. The r.m.s. coplanarity of the washer gaps was measured to be <5 μm, consistent with the required micro-alignment.
DOI •	reference for this paper ※ https://doi.org/10.18429/JACoW-IPAC2019-THPTS087
About •	paper received ※ 17 May 2019 paper accepted ※ 23 May 2019 issue date ※ 21 June 2019
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Paper

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Other Keywords

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MOPGW002

Longitudinal Kicker Design for Sirius Light Source

cavity, kicker, HOM, feedback

57

H.O.C. Duarte, A. Barros
LNLS, Campinas, Brazil

An overloaded cavity kicker for the Sirius longitudinal bunch-by-bunch feedback system will be presented in this contribution. 4th generation light sources’ lower aperture of vacuum chambers lead to higher cutoff frequencies, jeopardizing the electromagnetic performance of cavities by trapping higher order modes (HOMs) inside the structure. With the objective of damping longitudinal and transverse HOMs without compromising the kicker shunt impedance, solutions as cavity radius reduction, tapered transitions and other geometry changes are discussed herein.

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reference for this paper ※ https://doi.org/10.18429/JACoW-IPAC2019-MOPGW002

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paper received ※ 15 May 2019 paper accepted ※ 17 May 2019 issue date ※ 21 June 2019

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MOPGW004

Microphonics Suppression in ARIEL ACM1 Cryomodule

cavity, cryomodule, linac, pick-up

65

Y. Ma, K. Fong, J.J. Keir, D. Kishi, S.R. Koscielniak, D. Lang, R.E. Laxdal, R.S. Sekhon
TRIUMF, Vancouver, Canada

Now the stage of the 30MeV portion of ARIEL (The Advanced Rare Isotope Laboratory) e-Linac is under commissioning which includes an injector cryomodule (ICM) and the 1st accelerator cryomodule (ACM1) with two cavities configuration. The two ACM1 cavities are driven by a single klystron with vector-sum control and running in CW mode. During the commissioning, the ACM1 cavities gradient and stability was limited by ponderomotive effect. Acoustic noise from the environment vibration generated by cooling water system, cryogenic system and vacuum system have been identified to certain external source and some damping has been installed. In this paper, the progress of the microphonics suppression of ACM1 is presented.

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reference for this paper ※ https://doi.org/10.18429/JACoW-IPAC2019-MOPGW004

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paper received ※ 01 May 2019 paper accepted ※ 23 May 2019 issue date ※ 21 June 2019

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MOPGW047

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

cavity, simulation, timing, 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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MOPGW061

Radiation from a Dielectrically Loaded Waveguide with Open End

vacuum, radiation, embedded, acceleration

228

S.N. Galyamin, A.A. Grigoreva, A.V. Tyukhtin, V.V. Vorobev
Saint Petersburg State University, Saint Petersburg, Russia
A. Aryshev
KEK, Ibaraki, Japan

Funding: Work supported by Russian Science Foundation (Grant No. 18-72-10137).
Open-ended waveguide structures with dielectric loading excited by specially prepared electron bunches are considered as promising candidates for development of contemporary sources of Terahertz (THz) radiation. Despite of the fact that both ordinary vacuum THz devices (e.g., backward wave oscillator) are widely available and other mechanisms for THz generation are discussed, beam driven sources are still extremely attractive due to the extraordinary peak power of THz radiation*. In this report, we study electromagnetic (EM) field produced by a charged particle bunch exiting an open-ended circular waveguide with dielectric filling placed inside collinear vacuum waveguide of a larger radius. Based on the previously developed theory**, we mainly investigate Cherenkov radiation generated penetrated vacuum regions of the structure due to the diffraction mechanism. We pay attention to the case of a train of short bunches resulting in high-order Cherenkov modes excitation. We also develop analytical procedure allowing performing the limiting process to the case of infinite radius of the outer waveguide.
* B.D. O’Shea et al., Nature Communications, Vol. 7, P. 12763, (2016).
** S.N. Galyamin et al., J. Instrumentation, Vol. 13, P. C02012 (2018).

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reference for this paper ※ https://doi.org/10.18429/JACoW-IPAC2019-MOPGW061

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MOPGW064

On Wakefield in Dielectric Waveguide with Shallow Corrugation of Metallic Wall

radiation, ECR, wakefield, impedance

237

A.V. Tyukhtin, E.R. Akhmatova, T.Yu. Alekhina, 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).
Bunch radiation in periodical waveguides was mainly analyzed for situations when wavelengths are comparable to the structure period (Smith-Purcell emission). However, it is also of interest to study the "long-wave radiation" with wavelengths which are much larger than the structure period*,**. In such situation, the exact boundary conditions on the complicated periodic surface can be replaced with the equivalent boundary conditions (EBC) which must be fulfilled on the smooth surface. Earlier we considered with this approach radiation of the bunch moving along the axis of circular vacuum corrugated waveguide**. Comparison of analytical results with COMSOL simulations showed high accuracy of the EBC method. Here we analyze an analogous problem for the waveguide with corrugated wall and dielectric filling under condition that Cherenkov effect takes place in the dielectric. Due to this fact the radiation differs radically from that in the vacuum waveguide. At the same time, the radiation has essential differences from the one in the usual dielectric waveguide. The radiation properties in the waveguide under consideration and its differences from the radiation in the waveguide with smooth wall are analyzed.
* G. Stupakov, K. Bane, Phys. Rev. ST-AB, 15 (2012) 124401.
** A.V. Tyukhtin et al, J. of Instrumentation, 13 (2018) C04009.

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reference for this paper ※ https://doi.org/10.18429/JACoW-IPAC2019-MOPGW064

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

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MOPGW067

On Coordinate Systems in Beam Dynamics

simulation, 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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reference for this paper ※ https://doi.org/10.18429/JACoW-IPAC2019-MOPGW067

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

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MOPGW114

Bayesian Approach for Linear Optics Correction

quadrupole, optics, lattice, distributed

390

Y. Li, W.X. Cheng, R.S. Rainer
BNL, Upton, Long Island, New York, USA

With a Bayesian approach, the linear optics correction algorithm for storage rings is revisited. In modern ring-based accelerators, optics corrections are determined from repetitive measurements which help identify systematic and random quadrupole errors in presence of various measurement noises. This process is a multivariate nonlinear regression problem driven by either a completed lattice model or a Jacobian matrix. Starting from the Bayes’ theorem, ’likelihood functions’ and ’prior probability’ distributions are extracted from a complete linear optics model. Under some assumptions, the least square algorithm and then the Jacobian matrix approach can be re-derived. The coherence of the correction algorithm is ensured through specifying a self-consistent regularization coefficient to prevent overfitting. Optimal weights for different correction objectives are obtained based on their measurement noise level. A new technique has been developed to resolve degenerated quadrupole errors when observed at a few select BPMs. A necessary condition of being distinguishable is that their optics response vectors seen at these specific BPMs should be near-orthogonal.

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reference for this paper ※ https://doi.org/10.18429/JACoW-IPAC2019-MOPGW114

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

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MOPRB022

Current Status of the High-Power RF Systems During Phase2 Operation in SuperKEKB

klystron, cavity, operation, status

619

K. Watanabe, K. Marutsuka, Ma. Yoshida, S.I. Yoshimoto
KEK, Ibaraki, Japan

The SuperKEKB is an asymmetric-energy two-ring collider consisting of the high-energy ring (HER) for 7 GeV electrons and the low-energy ring (LER) for 4 GeV positrons at KEK. Both the electron and positron beams are injected from the Linac injector complex, which includes a newly constructed 1.1 GeV positron damping ring (DR) to supply a high-quality low emittance positron beam to the LER. The high power RF system has a role to drive the ARES cavities and the superconducting RF cavities for the SuperKEKB. The operating frequency of RF system is 508.9 MHz. The required RF power from the klystron at maximum storage beam current is ~850 kW (CW). The number of RF stations is total 31 for the main ring (MR) and DR. The status of each high power RF components, troubles of them and operation condition that occurred during phase 2 commissioning from Feb 2018 to July 2018 will be reported in this paper.

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reference for this paper ※ https://doi.org/10.18429/JACoW-IPAC2019-MOPRB022

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

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MOPRB056

THz Radiator Based on Photonic Band Gap Crystal for SwissFEL

electron, photon, experiment, FEL

693

L. Shi, R. Ischebeck, S. Reiche
PSI, Villigen PSI, Switzerland

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 701647.
The electromagnetic radiation in 1-20 THz has many unique properties when it interacts with matter due to its non-ionizing excitation in matter. Especially the dynamics of the excited matter can be probed with the help of X-ray pulses at a free electron laser facility, e.g. SwissFEL, to deepen our understanding of a wide range of phenomena. Due to its high research potential, various means of THz generation have been proposed and demonstrated. We investigate preliminarily here its generation based on a relativistic electron bunch and a photonic band gap crystal (PBG) made of dielectric rods. The PBG provides additional degrees of freedom for the THz pulse tuning. Additionally, the unwanted radiation parts can be damped by the structure in order to minimize the deleterious beam dynamics effects. The crystal also promises the integration of generation, filtering and coupling for transport into a single piece.

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reference for this paper ※ https://doi.org/10.18429/JACoW-IPAC2019-MOPRB056

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

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MOPRB067

High-gradient Single Cycle Terahertz Accelerating Structures

gun, acceleration, cathode, electron

731

S.P. Antipov, E. Gomez, S.V. Kuzikov
Euclid TechLabs, LLC, Solon, Ohio, USA
A.A. Vikharev
IAP/RAS, Nizhny Novgorod, Russia

Recently, gradients on the order of 1 GV/m level have been obtained in a form of single cycle (~1 ps) THz pulses produced by conversion of a high peak power laser radiation in nonlinear crystals (~1 mJ, 1 ps, up to 3% conversion efficiency). These pulses however are broadband (0.1-5 THz) and therefore a new accelerating structure type is required. For electron beam acceleration with such pulses we propose arrays of parabolic focusing micro-mirrors with common central. These novel structures could be produced by a femtosecond laser ablation system developed at Euclid Techlabs. This technology had already been tested for production of several millimeters long, multi-cell structure which has been testing with electron beam. We also propose using of structures where necessary GV/m E-fields are excited by a drive bunch travelling in the corrugated waveguide. The radiated by drive bunch sequence of short range delayed wakes are guided in this case by metallic disks and reflected back being focused exactly at time when the witness bunch arrives.

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reference for this paper ※ https://doi.org/10.18429/JACoW-IPAC2019-MOPRB067

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paper received ※ 21 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

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

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MOPTS050

VSWR Adjustment for ACS Cavity in J-PARC LINAC

cavity, coupling, simulation, 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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reference for this paper ※ https://doi.org/10.18429/JACoW-IPAC2019-MOPTS050

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

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TUXXPLM2

SRF Cavity Fault Classification Using Machine Learning at CEBAF

cavity, cryomodule, SRF, operation

1167

A.D. Solopova, A. Carpenter, T. Powers, Y. Roblin, C. Tennant
JLab, Newport News, Virginia, USA
K.M. Iftekharuddin, L. Vidyaratne
ODU, Norfolk, Virginia, USA

The Continuous Electron Beam Accelerator Facility (CEBAF) at Jefferson Lab is the first large high power CW recirculating electron accelerator which makes use of SRF accelerating structures configured in two antiparallel linacs. Each linac consists of twenty C20/C50 cryomodules each containing eight 5-cell cavities and five C100 upgrade cryomodules each containing eight 7-cell cavities. Accurately classifying the source of cavity faults is critical for improving accelerator performance. In addition to archived signals sampled at 10 Hz, a cavity fault triggers a waveform acquisition process where 16 waveform records sampled at 5 kHz are recorded for each of the 8 cavities in the effected cryomodule. The waveform record length is sufficiently long for transient microphonic effects to be observable. Significant time is required by a subject matter expert to analyze and identify the intra-cavity signatures of imminent faults. This paper describes a path forward that utilizes machine learning for automatic fault classification. Post-training identification of the physical origins of faults are discussed, as are potential machine-trained model-free implementations of trip avoidance procedures. These methods should provide new insights into cavity fault mechanisms and facilitate intelligent optimization of cryomodule performance

Slides TUXXPLM2 [4.404 MB]

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

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TUPMP051

MULTIPACTOR SUPPRESSION BY LASER ABLATION SURFACE ENGINEERING FOR SPACE APPLICATIONS

electron, laser, multipactoring, controls

1365

R. Valizadeh, A.N. Hannah, O.B. Malyshev, B.S. Sian
STFC/DL/ASTeC, Daresbury, Warrington, Cheshire, United Kingdom
J.S. Colligon
University of Huddersfield, Huddersfield, United Kingdom
Y. Dan
Hitachi High-Technologies Corp., Ibaraki-ken, Japan
V.R. Dhanak
The University of Liverpool, Liverpool, United Kingdom
J. Mutch
STFC/DL, Daresbury, Warrington, Cheshire, United Kingdom
B.S. Sian
UMAN, Manchester, United Kingdom
N. Sykes
Micronanics Laser Solution Center, Didcot, United Kingdom

Developing a surface with low Secondary Electron Yield (SEY) is one of the main ways of mitigating electron cloud and beam-induced electron multipacting in high-energy charged particle accelerators and space-borne RF equipment for communication purposes. In this study we report on the secondary electron yield (SEY) measured from silver coated aluminium alloy as-received and after laser ablation surface engineering (LASE). Analysis shows the SEY can be reduced by 43% using LASE. EDX and SEM analysis shows it is possible to reduce the SEY whilst maintaining the original surface composition.

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reference for this paper ※ https://doi.org/10.18429/JACoW-IPAC2019-TUPMP051

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paper received ※ 14 May 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, simulation, 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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TUPGW098

Fabrication & Cold Tests of a Millimeter-Period RF Undulator

undulator, laser, FEL, electron

1643

F. Toufexis, B.J. Angier, D. Gamzina, S.G. Tantawi
SLAC, Menlo Park, California, USA

Funding: This project was funded by U.S. Department of Energy under Contract No. DE-AC02-76SF00515, and the National Science Foundation under Contract No. PHY-1415437.
To reduce the linac energy required for an FEL radiating at a given wavelength, and hence its size, a smaller undulator period with sufficient field strength is needed. Previous work from our group successfully demonstrated a microwave undulator at 11.424GHz, using a corrugated cylindrical waveguide operating at the HE11 modes. We have designed a mm-wave undulator cavity at 91.392GHz* with an equivalent undulator period of 1.75 mm. This undulator requires 1.4 MW for sub microsecond pulses for an equivalent K value of 0.1. In this work we present the mechanical design and fabrication of this 91.392 GHz RF Undulator, as well as preliminary cold test data.
* F. Toufexis and S.G. Tantawi, "A 1.75-mm Period RF-Driven Undulator", Proceedings of IPAC17.

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

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TUPGW099

Superconducting Crab Cavity Options for Short X-Ray Pulse Generation in SPEAR3

cavity, sextupole, impedance, HOM

1647

F. Toufexis, V.A. Dolgashev, X. Huang, Z. Li
SLAC, Menlo Park, California, USA

Funding: This project was funded by U.S. Department of Energy under Contract No. DE-AC02-76SF00515.
We are exploring methods to generate short X-ray pulses in SPEAR3 on the order of 1 ps to enable studying ultrafast processes in materials. We are developing a 2-frequency crab cavity scheme with two sets of crab cavities* at the 6th and 6.5th harmonics of the 476 MHz ring RF frequency. In previous work we studied a normal conducting crab cavity for SPEAR3**. In this work we explored two superconducting cavity options: a traditional elliptical cavity and the Quasi-waveguide Resonator***. We found that the Quasi-waveguide Resonator cannot meet our field uniformity specifications due to higher order multipole fields. We then optimized a traditional elliptical cavity with the input, Lower Order Modes, and Higher Order Modes couplers following the Argonne Advanced Photon Source design.
* A. Zholents, et al, Nucl. Instrum. Methods Phys. Res., Sect. A, Vol. 425 (1999), p. 385.
** Z. Li, et al, Proceedings of IPAC17.
*** A. Lunin, et al, Proceedings of HOMSC14.

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

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TUPGW108

Characterization of NEG Coatings for SLS 2.0

impedance, resonance, coupling, vacuum

1662

M.M. Dehler, A. Citterio
PSI, Villigen PSI, Switzerland
S. Alberti, J.P. Hogge
SPC-EPFL, Lausanne, Switzerland
M. Hahn, H.P. Marques
ESRF, Grenoble, France
X.Y. Liu
USTC/NSRL, Hefei, Anhui, People’s Republic of China

To limit desorption and ameliorate pumping of the narrow 20 mm aperture vacuum chamber of SLS2.0, it is planned to fully coat it with nonevaporable getter (NEG) material. NEG coating can be produced with different structural characteristics, from dense films to columnar growth, with corresponding distinct electrical properties affecting the machine impedance and the instability threshold of the accelerator. In order to evaluate and characterize the coating process for geometries similar to the SLS chamber, we measured the resonance properties of coated and uncoated shorted waveguide pieces. First tests were done with standard X band waveguides at 12 and 7 GHz. Test setups using elliptical cross sections are in preparation, also for higher frequencies allowing the characterization of thin NEG layers. The final goal is to have a standardized process to test of samples coated by external producers. We describe the setups and first results.

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

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TUPRB002

The Conceptual Design of a 36 GHz RF Undulator

undulator, cavity, electron, photon

1676

D. Zhu
ASCo, Clayton, Victoria, Australia
A.W. Cross, L. Zhang
USTRAT/SUPA, Glasgow, United Kingdom
Y.E. Tan
AS - ANSTO, Clayton, Australia

The CompactLight project supported by European H₂020 is to design a hard X-ray FEL facility beyond today’s state of the art. The project integrates photo injector, X-band acceleration and innovative compact short-period undulators together to make the machine more compact. RF undulator has an extraordinary advantage of working at very short undulator period. A conceptual design for a RF undulator at 36 GHz using a corrugated cylindrical waveguide operating in the HE11 mode is presented in this paper. Based on beam dynamics simulation and photon beam radiation simulations, the possibility of RF undulator to be used in CompactLight project is evaluated.

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

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TUPRB015

Cryogenic, in-Vacuum Magnetic Measurement Setup for Superconducting Undulators

vacuum, undulator, detector, synchrotron

1709

A.W. Grau, S. Casalbuoni, N. Glamann, D. Saez de Jauregui
KIT, Eggenstein-Leopoldshafen, Germany

The magnetic field quality has a strong impact on the performance of insertion devices (IDs) when installed in synchrotron light sources. Superconducting IDs have the advantage to produce a higher magnetic peak field for a given gap and period length than IDs assembled with permanent magnets. Before installation of a superconducting ID in a synchrotron light source it is of fundamental importance to characterize the magnetic properties by accurate field and field integral measurements. We follow this aim within our R&D program for superconducting undulators (SCUs). In this contribution, we describe the equipment and the challenges of a cryogenic, in vacuum measurement setup to perform magnetic measurements of the local field, the field integrals and the multipole components of in vacuum SCUs assembled in the final cryostat.

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

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TUPRB045

Stimulated Excitation by Seeding With Cherenkov Radiation in an Optical Cavity

radiation, cavity, electron, ion-source

1785

S.M. Jiang, Z.G. He, Q.K. Jia, W.W. Li, L. Wang
USTC/NSRL, Hefei, Anhui, People’s Republic of China
D. He
Anhui Electrical Engineering Professional Technique College, Hefei, People’s Republic of China

Funding: Work supported by National Foundation of Natural Sciences of China (11775216, 11705198, 11675178), and Fundamental Research Funds for the Central Universities (WK2310000061).
By seeding with narrow-band Cherenkov radiation from a dielectric loaded waveguide(DLW), stimulated excitation in an optical cavity is presented. The evolution and energy loss of the field oscillating in optical cavity is analysed by the theoretical and numerical calculation. The results show that the high order TM modes of the Cherenkov radiation can be better preserved after a large number of roundtrips in the optical cavity and this scheme offers a potential method of realizing high power Terahertz radiation source in a compact facility.

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paper received ※ 30 April 2019 paper accepted ※ 18 May 2019 issue date ※ 21 June 2019

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TUPRB050

The Optical Resonator of CTFEL for Range of 1 to 2 THz

FEL, radiation, electron, coupling

1795

X.J. Shu, Y.H. Dou
Institute of Applied Physics and Computational Mathematics, People’s Republic of China

A high power THz free electron laser (FEL) facility is under construction at China Academy of Engineering Physics (CTFEL). The radiation frequency of the FEL facility will be tuned in range of 1~3 THz and the average output power is about 10 W. The system mainly consists of a GaAs photoemission DC gun, superconductor accelerator, hybrid wiggler, optical cavity. The first lasing is obtained on Aug. 29, 2017, and CTFEL is operated in range of 2-4THz, but cannot lasing at the frequency below 1.8 THz. The optical resonator of CTFEL must be optimized to ensure lasing in range of 1 to 2 THz.. The lasing strongly depends on the performance of the optical resonator including output efficiency, gain and round-trip loss. The optical resonator consists of metal-coated reflect mirror, the centre-hole output mirror, waveguide. The influence of waveguide on the quality of optical cavity is evaluated by the 3D OSIFEL code. The waveguide size and output hole radius is optimized to different frequencies between 1 THz to 2 THz.

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paper received ※ 13 May 2019 paper accepted ※ 24 May 2019 issue date ※ 21 June 2019

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TUPRB094

New Superconducting Undulator Magnetic Measurement System for the Advanced Photon Source Upgrade

undulator, photon, vacuum, storage-ring

1881

M. Kasa, E.R. Anliker, Y. Ivanyushenkov, Y. Shiroyanagi
ANL, Argonne, Illinois, USA

Funding: Work supported by the U.S. Department of Energy, Office of Science, under Contract No. DE-AC02-06CH11357.
Magnetic measurements of existing superconducting undulators (SCUs) are performed under normal operating conditions after final assembly into the cryostat and before installation on the Advanced Photon Source (APS) storage ring. The SCU cryostat for the APS upgrade has been scaled in length from the current cryostat and will contain two SCUs. While some aspects of the current measurement system are desirable to retain, such as a room temperature measurement bore, scaling the current measurement techniques to the length required for the APS upgrade cryostat is not feasible. To address these challenges a unique system has been developed at the APS to allow measurements of the two SCU magnets in the long cryostat. The measurement system developed allows the magnets to be operated under normal operating conditions while maintaining the measurement equipment at room temperature and atmospheric pressure.

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

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TUPTS065

RF Conditioning of the CLARA 400 Hz Photoinjector

cavity, controls, vacuum, operation

2067

L.S. Cowie, D.J. Scott
STFC/DL/ASTeC, Daresbury, Warrington, Cheshire, United Kingdom

Automated conditioning of the 400 Hz photoinjector for CLARA was begun and the conditioning program refined. The conditioning was performed at 100 Hz. Masks were used to detect breakdowns in the reflected power and phase, and the breakdown rate was limited to 5x106 breakdowns per pulse. The cavity gradient and breakdown rate evolution over the conditioning time is presented. Post-pulse multipactor and other evidence of electron effects were detected. Possible mechanisms for this are discussed. The conditioning was interrupted by breakdown in the waveguide after reaching 2.5 MW, and will be resumed after the planned 6 month shutdown of CLARA.

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

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WEPMP044

Mu2e Electrostatic Septa Volumetric Exchange of Fc-40 Dielectric in High Radiation Environments

radiation, septum, cathode, extraction

2434

M.L. Alvarez, A. Deshpande, K.R. Hunden, V.P. Nagaslaev, E. Pirtle
Fermilab, Batavia, Illinois, USA

Funding: * Operated by FRA, LLC under Contract No. DEAC02-07CH11359 and Grant Award No. LAB 18-1802 with the United States Department of Energy.
Two electrostatic septa (ESS) are being designed for the slow extraction of 8 GeV proton beam for the Mu2e experiment at Fermilab. Special attention is given to the high voltage feedthrough (HVF), which energizes the cathode creating the bending field. The FC-40 dielectric fluid, surrounding the HV cable breaks down from radiation exposure, which reduces its insulating capabilities. The new HVF design focuses on effective replacement of the exposed fluid and eliminating the stagnant areas of low exchange rate. A preliminary test using a fully transparent prototype HVF and water was conducted to understand the volumetric exchange rate of the high radiation region. Here we discuss the results of these tests and further studies using the FC-40.
** malvare4@fnal.gov
*** vnagasl@fnal.gov

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reference for this paper ※ https://doi.org/10.18429/JACoW-IPAC2019-WEPMP044

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

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WEPGW003

High-Level Applications for the Sirius Accelerator Control System

EPICS, controls, MMI, linac

2462

X.R. Resende, L. Liu, A.C.S. Oliveira, F.H. de Sá, G.L. do Prado
LNLS, Campinas, Brazil

Sirius is the new 3 GeV low-emittance Brazilian Synchrotron Light source under installation and commissioning at LNLS. The machine control system is based on EPICS and when the installation is complete it should have a few hundred thousand process variables in use. For flexible integration and intuitive control of such sizable system a considerable number of high-level applications, input/output controllers and graphical user interfaces have been developed, mostly in Python, using a variety of libraries, such as PyEpics, PCASPy and PyDM. Common support service applications (Archiver Appliance, Olog, Apache server, a mongoDB-based configuration server, etc) are used. Matlab Middle Layer is also an available option to control EPICS applications. Currently system integration tests are being performed concomitant with initial phases of accelerator commissioning and installation. A set of functionalities is already available: Linac’s control; timing subsystem control; machine snapshots; optics measurements and correction; magnets settings and cycling; Booster orbit acquisition and correction, and so on. From the experience so far, subsystems communications have worked satisfactorily but there has been a few unexpected component performance. In this paper we discuss this experience and descrive the libraries and packages used in high-level control system , as well as the difficulties faced to implement and to operate them.

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reference for this paper ※ https://doi.org/10.18429/JACoW-IPAC2019-WEPGW003

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

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WEPGW045

Application of Clustering by Fast Search and Find of Density Peaks to Beam Diagnostics at SSRF

SRF, storage-ring, diagnostics, electron

2581

R. Jiang, Y.B. Leng
SSRF, Shanghai, People’s Republic of China

With the increased technological complexity of accelera-tors, meeting the demand of beam diagnostics and opera-tion need more powerful and faster methods. And detect-ing the accuracy and stability of beam position moni-tors(BPMs) are important for all kinds of measurement systems and feedback systems in particle accelerator field. As an effective tool for data analysis and automa-tion, the machine learning methods had been used in accelerator physics field, recently. Among machine learn-ing methods, the clustering by fast search and find of density peaks as a typical unsupervised learning algo-rithms could be performed directly without training in arbitrary accelerator systems and could discover un-known patterns in the data. This paper used clustering by fast search and find of density peaks to detect faulty beam position monitor or monitoring beam orbit stability by analysis five typical parameters, that is beta oscilla-tion of X and Y direction(BetaX and BetaY), transverse oscillation of X and Y direction(AmpX and AmpY) and energy oscillation(AmpE). The results showed that cluster-ing by fast search and find of density peaks could classi-fy beam data into different clusters on the basis of their similarity. And that, aberrant run data points could be detected by decision graph. Morever, analysis results demonstrate the characteristic parameters AmpE, AmpX and BetaX amplitude have the same effect to distinguish the faulty BPMs and the AmpY and the BetaY amplitude are also.

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reference for this paper ※ https://doi.org/10.18429/JACoW-IPAC2019-WEPGW045

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

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WEPGW074

MYRRHA DAQ Development

controls, EPICS, LabView, software

2645

R. Modic
Cosy lab, Ljubljana, Slovenia
P. Della Faille, D. Vandeplassche
SCK•CEN, Mol, Belgium
P. Mekuc
Cosylab, Ljubljana, Slovenia

An approach to a generic Data Acquisition (DAQ) solution for the MYRRHA test stand at Louvain-la-Neuve (Belgium) will be described in this paper. Need for better sampling performance, signal quality, arbitrary processing and storage of measurements was a motivation for this work. A full integration of the DAQ system in the global EPICS control environment was a strong requirement. An intermediate DAQ platform was put in place to satisfy the control and experiment needs. The NI PXI platform is selected to minimize integration and development effort. NI LabVIEW is used to create a generic DAQ application. CALab library supported by BESSY is used to connect LabVIEW and EPICS. CSS GUI provides the user with the necessary control, visualization and configuration capability. The technical and organizational approach to the collaboration will be detailed in the paper. Necessary customizations of CSS and CALab and experience on using NI PXI for DAQ platform will be explained.

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reference for this paper ※ https://doi.org/10.18429/JACoW-IPAC2019-WEPGW074

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

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WEPGW115

Radiation Robust RF Gas Beam Detector R&D for Intensity Frontier Experiments

detector, cavity, plasma, electron

2770

K. Yonehara, A. Moretti
Fermilab, Batavia, Illinois, USA
M.A. Cummings, R.P. Johnson, G.M. Kazakevich
Muons, Inc, Illinois, USA

A novel radiation robust RF gas beam detector has been demonstrated by using the Main Injector beam at Fermilab. The detector demonstrated a stable signal gain, fast response time, and high radiation resistivity with intense proton beams. The plasma process in the detector is studied to validate the plasma physics model. The result suggests that the detector is applicable for Long Baseline Neutrino Facility at Fermilab. To prepare for the LBNF, a proto type detector will be made and applied for the Neutrino at Main Injector target system. Progress of the project will be given in the presentation.

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reference for this paper ※ https://doi.org/10.18429/JACoW-IPAC2019-WEPGW115

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

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WEPGW116

LHC Optics Measurement and Correction Software Progress and Plans

optics, software, coupling, MMI

2773

R. Tomás, F.S. Carlier, J.M. Coello de Portugal, J. Dilly, E. Fol, A. Garcia-Tabares, M. Hofer, E.H. Maclean, L. Malina, T.H.B. Persson, P.K. Skowroński, M.L. Spitznagel, A. Wegscheider, J. Wenninger
CERN, Geneva, Switzerland
J.F. Cardona, Y. Rodriguez
UNAL, Bogota D.C, Colombia
F.S. Carlier
NIKHEF, Amsterdam, The Netherlands
D. Esperante Pereira, J. Fuster, D. Gonzalez-Iglesias
IFIC, Valencia, Spain
R. Hoekstra
KVI, Groningen, The Netherlands

LHC Optics Measurements and Corrections (OMC) require efficient on-line software applications to acquire and analyze data and to compute the necessary corrections. During Run 2 various measurement and correction techniques have been merged to yield unprecedented optics quality, increasing the required number of steps to finalize the optics commissioning and the size of the software project. In turn, this calls for a higher level of automation, where machine learning techniques are being implemented. During the Long Shutdown 2 a large refactoring of the codes will be in place to improve performance, maintainability and extensibility. A description of the current status of the software and future plans is given.

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reference for this paper ※ https://doi.org/10.18429/JACoW-IPAC2019-WEPGW116

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paper received ※ 07 May 2019 paper accepted ※ 21 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

brightness, quadrupole, simulation, 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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WEPRB034

Study on the Design of the X-band Waveguide-damped Structure

wakefield, damping, HOM, simulation

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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WEPRB039

Tuning of a Tapered Ridge-Loaded Waveguide Coupler for a Drift Tube LINAC of the Compact Pulsed Hadron Source

coupling, DTL, linac, target

2893

Y. Lei, C.T. Du, X. Guan, R. Tang, X.W. Wang, Q.Z. Xing, S.X. Zheng
TUB, Beijing, People’s Republic of China

This paper presents the tuning result of a tapered ridge-loaded waveguide coupler for the drift tube linac (DTL) of the compact pulsed hadron source (CPHS) at Tsinghua University. The coupler has been designed, manufactured, and mounted on the DTL cavity for the cold measurement and tuning. The iris diameter of the coupler which is related to the coupling coefficient needs to be determined in the tuning experiment, due to the difference between the designed and measured quality factors. Meanwhile, we found that the relationship between the coupling coefficient and iris diameter from the traditional analytical design method is not applicable when the iris diameter is relatively large. In this paper, the target coupling coeffi-cient is analysed, and the limit of the original analytical design is presented. The measurement method is intro-duced to improve the measurement efficiency and the tuning process of the coupling coefficient to the target value is described. After several iterations, the coupling coefficient is tuned to 1.54 which is close to the desired value of 1.56.

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reference for this paper ※ https://doi.org/10.18429/JACoW-IPAC2019-WEPRB039

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

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WEPRB042

High Power Test of the First C-band Spherical Pulse Compressor Prototype

cavity, FEL, electron, linac

2896

Z.B. Li
SINAP, Shanghai, People’s Republic of China
W. Fang, Q. Gu, X.X. Huang, J.H. Tan, Z.T. Zhao
SSRF, Shanghai, People’s Republic of China

Funding: National Natural Science Foundation of China (No. 11675249)
Recently, a new C-band (5712 MHz) compact spherical radio frequency (RF) pulse compressor was designed and tested for Shanghai Soft X-ray Free Electron Laser Facili-ty (SXFEL). This pulse compressor utilizes one high Q₀ spherical RF resonant cavity that works with two TE1, 1,3 modes and a dual-mode polarized coupler. The peak power multiply factor is 6.1 and average power gain 3.8 in theory. During the high power test, a peak power mul-tiply factor of 5.74 and average power gain of 3.77 was achieved. This paper presents the RF measurement of the C-band spherical pulse compressor and the high power test results.

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reference for this paper ※ https://doi.org/10.18429/JACoW-IPAC2019-WEPRB042

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

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WEPRB043

Wakefield Suppression in the Main LINAC of the Klystron-Based First Stage of CLIC at 380 GeV

wakefield, HOM, damping, linac

2899

J.Y. Liu, H.B. Chen, J. Shi, H. Zha
TUB, Beijing, People’s Republic of China
A. Grudiev
CERN, Meyrin, Switzerland

An alternative klystron-based scenario for the first stage of Compact Linear Collider (CLIC) at 380 GeV centre-of-mass energy was proposed. To preserve the beam stability and luminosity of CLIC, the beam-induced transverse long-range wakefield in main linac must be suppressed to an acceptable value. The design of klystron-based accelerating structure is based on waveguide damping structure (WDS). The high-order modes (HOMs) propagating into four waveguides are absorbed by HOM damping loads. In this paper, the wakefield suppression in CLIC-K based on GdfidL code simulations are presented.

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reference for this paper ※ https://doi.org/10.18429/JACoW-IPAC2019-WEPRB043

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paper received ※ 14 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

vacuum, simulation, 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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WEPRB047

High-Power Test of a 12 Cell Accelerating Structure Build in Halves

klystron, vacuum, shielding, ECR

2912

M.M. Peng, Y.L. Jiang, J.Y. Liu, Z.N. Liu, X.C. Meng, J. Shi, H. Zha
TUB, Beijing, People’s Republic of China

An X-band 12 cell travelling-wave accelerating structure has been developed and high-power tested at Tsinghua University in China. This structure works at 2⁄3 π at the frequency of 11.424 GHz. It is a 12-cell constant-impedance structure build in halves and was silver-brazed as a vacuum tight structure. The high power test was conducted at Tsinghua X-band high power test facility [1] with a 50-MW X-band klystron at a repetition rate to 40 Hz. The final input power was 51.23 MW with a 200 ns pulse width, which means an accelerating gradient of 88.58 MV/m was reached. This paper presents the high power test results including the gradient and breakdown history.

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reference for this paper ※ https://doi.org/10.18429/JACoW-IPAC2019-WEPRB047

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paper received ※ 10 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

simulation, cavity, 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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WEPRB052

Design of Two Types of X-Band High Power Directional Coupler

coupling, simulation, 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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WEPRB058

Combined Field Emission and Multipactor Simulation in High Gradient RF Accelerating Structures

electron, multipactoring, simulation, cavity

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, HOM, simulation, 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

simulation, klystron, 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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WEPTS037

DC Beam Space-Charge Modeling for OpenXAL

simulation, space-charge, LEBT, solenoid

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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WEPTS081

An Analytic Approach to Emittance Growth from the Beam-Beam Effect with Applications to the LHeC

proton, emittance, electron, collider

3307

E.A. Nissen
JLab, Newport News, Virginia, USA
D. Schulte
CERN, Meyrin, Switzerland

Funding: Authored by Jefferson Science Associates, LLC under U.S. DOE Contract No. DE-AC05-06OR23177. The U.S. Government retains a non-exclusive, world-wide license to publish or reproduce this manuscript.
In colliders with asymmetric rigidity such as the proposed Large Hadron electron Collider, jitter in the weaker beam can cause emittance growth via coherent beam-beam interactions. The LHeC in this case would collide 7 TeV protons on 60 GeV electrons, which can be modeled using a weak-strong model. In this work we estimate the proton beam emittance growth by separating out the longitudinal angular kicks from an off-center bunch interaction and produce an analytic expression for the emittance growth per turn in systems like the LHeC.

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reference for this paper ※ https://doi.org/10.18429/JACoW-IPAC2019-WEPTS081

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paper received ※ 01 May 2019 paper accepted ※ 22 May 2019 issue date ※ 21 June 2019

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THPMP044

Radiation Hard Sensor for Reactor Applications

laser, radiation, timing, detector

3545

R.J. Abrams, M.A. Cummings, R.P. Johnson, T.J. Roberts
Muons, Inc, Illinois, USA
D.M. Kaplan
Illinois Institute of Technology, Chicago, Illinois, USA

A novel method of measuring temperature of the coolant inside a reactor core is presented. The method, which is both standoff and non-invasive, is based on the interaction between an ultrasonic pulse and a delayed light pulse in the coolant. In the interaction, the light pulse, which is scattered backward by Brillouin scattering, is frequency-shifted. The frequency shift is dependent on the temperature and other parameters of the coolant. The light pulses and the ultrasound pulses are generated and detected outside of the core.

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reference for this paper ※ https://doi.org/10.18429/JACoW-IPAC2019-THPMP044

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paper received ※ 14 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

simulation, 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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THPMP050

Progress on the Optics Modeling of BMI’s Ion Rapid-Cycling Medical Synchrotron at BNL

dipole, optics, focusing, simulation

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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THPGW033

Numerical Study of Photonic-Crystal-Based Dielectric Accelerators

photon, acceleration, electron, impedance

3653

G. Torrisi, L. Celona, S. Gammino, D. Mascali, G. Sorbello
INFN/LNS, Catania, Italy
C. De Angelis, A. Locatelli
University of Brescia, Brescia, Italy
G.S. Mauro
INFN/LNL, Legnaro (PD), Italy
G. Sorbello
University of Catania, Catania, Italy

All-dielectric electromagnetic band gap (EBG) waveguides structures promise significant improvement of accelerating gradient of laser-driven acceleration with the potential to miniaturize the accelerator itself. In this work we study photonic crystal structures designed for acceleration of relativistic electrons. We explore the performance of the all-dielectric EBG accelerating waveguide structures thanks to full wave electromagnetic simulations of couplers and accelerating waveguides. The characteristic interaction impedance, accelerating gradient and all the key parameters that are typically used to characterize linear accelerators are evaluated and used to compare the properties of the accelerating mode field distribution in different geometries.

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reference for this paper ※ https://doi.org/10.18429/JACoW-IPAC2019-THPGW033

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paper received ※ 30 April 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, simulation, 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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THPGW079

THz-Based Femtosecond MeV Electron Bunch Compression

electron, FEM, experiment, focusing

3766

M.A.K. Othman, M.C. Hoffmann, M.E. Kozina, R.K. Li, E.A. Nanni, X. Shen, E.J. Snively, X.J. Wang
SLAC, Menlo Park, California, USA

Funding: This work was supported by Department of Energy contract DE-AC02-76SF00515.
Probing structural dynamics at atomic spatial and ultrashort temporal scales reveals unprecedented details of fundamental behavior of nature, allowing for better understanding of intricate energy-matter interaction occurring at such scales. Developing state-of-the-art technology to access these details entails utilizing X-ray free-electron lasers (XFELs), ultrafast electron diffraction (UED), and advanced electron microscopes. In particular, ultrafast diffraction science received growing attention thanks to innovation in sources, detectors and instrumentation in general. Within this context, interest in laser-generated THz wave-matter interaction has recently emerged as a new regime for controlling electrons with high temporal precision. Previously, the SLAC UED team has demonstrated attosecond electron metrology using laser-generated single-cycle THz radiation, which is intrinsically phase locked to the optical drive pulses, to manipulate multi-MeV relativistic electron beams. Here we demonstrate further steps towards achieving ultrafast timing resolution that utilizes femtosecond electron bunches. The proposed setup allows for compressing electron beam bunches down to a femtosecond using interaction with high field single-cycle THz pulses. We demonstrate a novel design of a dispersion-free parallel-plate tapered waveguide that provides focusing of THz pulses achieving >100 MV/m field strength at the interaction point as measured by electro-optical sampling for ~7 μJ of incoming THz pulse energy. The structure is being designed and built for bunch compression experiments using the SLAC UED facility.

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reference for this paper ※ https://doi.org/10.18429/JACoW-IPAC2019-THPGW079

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

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THPRB038

ALARM SYSTEM OF IRFEL AT NSRL

FEL, controls, interface, EPICS

3896

X. Chen, C. Li, G. Liu, Z.X. Shao, Y. Song, J.G. Wang, K. Xuan
USTC/NSRL, Hefei, Anhui, People’s Republic of China

An InfraRed Free Electron Laser Light (IRFEL) is under commissioning at National Synchrotron Radiation Laboratory (NSRL). The control system of IRFEL is a distributed system based on Experimental Physics and Industrial Control System (EPICS). The alarm system is an essential part of the control system. It is developed based on the software Phoebus. The module named "Alarms" in Phoebus can store states and configuration information of the Process Variable (PV) in the Kafka topics. To meet our requirements, 3 kinds of alarm message distribution applications are developed, i.e. Web-Based GUI, WeChat and SMS. This paper will introduce the alarm system architecture and the implementations of the applications for alarm message distribution.

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reference for this paper ※ https://doi.org/10.18429/JACoW-IPAC2019-THPRB038

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

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THPRB079

DC Testing and Phase Resolved Partial Discharge Measurements of the New Trigger Transformers for the LHC Beam Dump Kickers

high-voltage, operation, kicker, power-supply

3998

T. Stadlbauer, A. Chmielinska, L. Ducimetière, D. Kontelis, T. Kramer, V. Senaj
CERN, Geneva, Switzerland

During LS2 the LHC beam dump kicker pulse generators will be subject to a substantial consolidation program. One major part is the replacement of the existing GTO stack trigger transformer by a new more performant one. The transformer is assembled, moulded and tested in-house. Part of the validation procedure are standard DC tests and subsequent discharge monitoring as well as newly introduced phase resolved partial discharge measurements. This paper briefly highlights the trigger transformer parameters and construction and outlines in detail the testing and partial discharge measurements. It concludes with a comparison and analysis of the results of the different measurement techniques.

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reference for this paper ※ https://doi.org/10.18429/JACoW-IPAC2019-THPRB079

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

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THPRB086

Design & Optimization of the Alignment Supports for the New Laminated Magnets for the CERN East Area Consolidation Project

alignment, radiation, operation, secondary-beams

4020

R. Vanhoutte, D. Brethoux, A. Ebn Rahmoun, S. Evrard, F.J. Harden, E. Harrouch, M. Lazzaroni, M. Lino Diogo dos Santos, R. Lopez, D.E. Nogtikov, J. Renedo Anglada
CERN, Meyrin, Switzerland

The East Area is one of CERNs experimental area, running since its foundation in 1958. Extracting a 24GeV proton beam from the Proton Synchrotron accelerator, the primary beam is divided into different secondary beams, serving various experiments and user’s facilities such as CLOUD, CHARM, IRRAD. Due to improved optics and an energy saving scheme, the facility will go under a renovation between 2019 and 2020, including the replacement of the magnets with new laminated ones to allow a cycled powering scheme. Those magnets need improved supports, and in some cases even a new design, to optimize the alignment operations in those areas. This article will mainly address the different proposed solutions for plug-in supports as well as for conventional ones.

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reference for this paper ※ https://doi.org/10.18429/JACoW-IPAC2019-THPRB086

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

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THPRB112

Commission of the Transverse Bunch-by-Bunch Feedback at SPEAR3

feedback, kicker, injection, vacuum

4081

K. Tian, W.J. Corbett, X. Huang, N. Kurita, D.J. Martin, J.A. Safranek, J.J. Sebek
SLAC, Menlo Park, California, USA
D. Teytelman
Dimtel, San Jose, USA

Funding: Work supported by US Department of Energy Contract DE-AC03-76SF00515.
Driven by the demand of suppressing transverse beam instabilities and developing novel short pulse operation modes in SPEAR3 storage ring, a wide-band transverse bunch-by-bunch feedback system has been recently commissioned for SPEAR3 storage ring. The system was demonstrated to be sufficient to suppress the transverse coupled bunch instabilities caused by trapped RF modes in one of the in vacuum insertion devices. A new function of beam instability interlock has been developed and is part of machine protection system for the in vacuum insertion device. In addition, the bunch-by-bunch feedback system serves as a indispensable diagnostic tool that enables us to measure machine parameters, beam impedance, and characteristics of the beam instability modes. In this paper, we describe the scheme and performance of the bunch-by-bunch feedback system at SPEAR3.

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reference for this paper ※ https://doi.org/10.18429/JACoW-IPAC2019-THPRB112

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

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THPRB116

Effect of Ground Motion Introduced by HL-LHC CE Work on LHC Beam Operation

ground-motion, luminosity, operation, civil-engineering

4092

M. Schaumann, D. Gamba, M. Guinchard, L. Scislo, J. Wenninger
CERN, Geneva, Switzerland

Funding: Research supported by the HL-LHC project
The official groundbreaking of the civil engineering (CE) work for the high luminosity upgrade of the LHC started on 15 June 2018 parallel to LHC beam operation. Compactor work and shaft excavation around the two low beta experiments, ATLAS and CMS, were expected to induce vibrations to the accelerator magnets and cause orbit disturbance, beam loss and potentially premature beam dumps. Ground motion sensors were installed on the surface and close to the triplets, where the CE works were expected to have the largest impact on the beams. This paper discusses the observations made on the LHC beams that could be correlated to CE work.

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reference for this paper ※ https://doi.org/10.18429/JACoW-IPAC2019-THPRB116

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

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THPTS008

Prospects of Additive Manufacturing for Accelerators

cavity, vacuum, niobium, detector

4118

N. Delerue, S. Jenzer
LAL, Orsay, France
H.C. Carduner
SUBATECH, Nantes, France
R.L. Gerard
CERN, Meyrin, Switzerland
P.M. Manil
CEA-DRF-IRFU, France
P.R. Repain
LPNHE, Paris, France
A. Simar
UCL, Louvain-la-Neuve, Belgium

Funding: Université Paris-SAclay, Labex P2IO and P2I departement
Additive manufacturing allows the production of mechanical components often much faster than traditional manufacturing. Several accelerators components built using additive manufacturing have already been qualified for use in accelerator. A workshop was held in Orsay in December 2018 to discuss the prospects of using additive manufacturing for particle accelerators and particle detectors. We report here on the prospects as far as accelerators are concerned.

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reference for this paper ※ https://doi.org/10.18429/JACoW-IPAC2019-THPTS008

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paper received ※ 20 May 2019 paper accepted ※ 22 May 2019 issue date ※ 21 June 2019

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THPTS039

DESIGN OF A COMPACT VARIABLE X-BAND RF POWER SPLITTER

impedance, klystron, electron, network

4194

F. Liu, H.B. Chen, J.Y. Liu, Z.N. Liu, J. Shi, H. Zha
TUB, Beijing, People’s Republic of China

This paper presents a design of a compact variable X-band RF power splitter. The RF power splitter includes one input port and two output ports, and the power divi-sion ratio can be adjusted by changing the position of a short circuit piston. This system keeps a good match (less than -40 dB) at any power division ratio. An E-bend waveguide structure is selected to make the geometry more compact (11cm in length, 3.5cm in width and 5 cm in height). Special studies was conducted to sustain a low surface electrical field (maximum 65 MV/m at 100 MW input), and large bandwidth (250MHz). This power split-ter is designed for high-power test stand at Tsinghua Uni-versity.

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reference for this paper ※ https://doi.org/10.18429/JACoW-IPAC2019-THPTS039

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

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THPTS063

Development of a W-Band Power Extraction Structure

cavity, undulator, electron, extraction

4252

F. Toufexis, B.J. Angier, D. Gamzina, A. McGuire, M. Shumail, S.G. Tantawi
SLAC, Menlo Park, California, USA

Funding: This project was funded by U.S. Department of Energy under Contract No. DE-AC02-76SF00515, and the National Science Foundation under Contract No. PHY-1415437.
We are modifying the X-Band Test Accelerator at SLAC to operate as an Extreme Ultra Violet (EUV) light source*. The existing photo electron gun will be replaced by a thermionic X-Band injector which utilizes RF bunch compression. The beam is accelerated up to 129 MeV using an X-Band traveling wave structure followed by a novel high shunt impedance standing wave structure. The beam then goes through a mm-wave undulator with a period of 1.75 mm, producing EUV radiation around 13.5 nm. The undulator is powered by a W-Band decelerator structure, which extracts the RF power from the electron beam. In this work we present the mechanical design and fabrication of the 91.392 GHz decelerator structure, as well as structural characterization of its cavities using SEM and 3D microscopy.
* F. Toufexis, et al, "A Compact EUV Light Source using a mm-wave Undulator", Proceedings of IPAC17.

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reference for this paper ※ https://doi.org/10.18429/JACoW-IPAC2019-THPTS063

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

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THPTS087

Micro-aligned Solenoid for Magnetized Bunched-beam Electron Cooling of 100 GeV/u Ions

electron, solenoid, alignment, collider

4314

P.M. McIntyre, J. Breitschopf, J. Gerity, J.N. Kellams
Texas A&M University, College Station, USA
J. Breitschopf, J. Gerity, J.N. Kellams, A. Sattarov
ATC, College Station, Texas, USA

Funding: This work is supported by grant DE-SC0018468 from the US Dept. of Energy.
Magnetized electron cooling of ion beams requires pre-cise alignment of the electron beam with the equilibrium trajectory of the ion bunch. For the parameters required for JLEIC, a solenoid with bore field ~1 T, length ~30 m, and rms alignment of ~μrad is required. Such precise alignment has never been accomplished in a 1 T solenoid. The design of a micro-aligned solenoid is presented. A gap-separated stack of thin steel washers is located inside the solenoid. The washer stack shields transverse magnet-ic fields from its interior by a factor of ~10. A 30-washer module of the structure was built and measured using ultra-sensitive capacitive probes using a coordinate meas-uring machine. The r.m.s. coplanarity of the washer gaps was measured to be <5 μm, consistent with the required micro-alignment.

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reference for this paper ※ https://doi.org/10.18429/JACoW-IPAC2019-THPTS087

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

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