IPAC2017 - List of Keywords (simulation)

Paper	Title	Other Keywords	Page
MOZA1	Electron Cloud Effects at the LHC and LHC Injectors	electron, operation, emittance, dipole	30
	G. Rumolo, H. Bartosik, E. Belli, P. Dijkstal, G. Iadarola, K.S.B. Li, L. Mether, A. Romano, M. Schenk, F. Zimmermann CERN, Geneva, Switzerland E. Belli University of Rome La Sapienza, Rome, Italy P. Dijkstal TU Darmstadt, Darmstadt, Germany M. Schenk EPFL, Lausanne, Switzerland
	Electron cloud effects are one of the main limitations of the performance of the LHC and its injectors. Enormous progress has been done in the simulation of the electron cloud build-up and of the effects on beam stability while mitigation measures have been identified and implemented (scrubbing, low secondary electron yield coatings, etc.). The above has allowed reaching nominal beam parameters in the LHC during Run 2. A review of the studies and results obtained and the strategy and expected performance for the High Luminosity operation of the LHC will be presented.
	Slides MOZA1 [12.855 MB]
DOI •	reference for this paper ※ https://doi.org/10.18429/JACoW-IPAC2017-MOZA1
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MOOCA1	High Efficiency Klystrons Using the COM Bunching Technique	klystron, electron, cavity, bunching	37
	D.A. Constable Lancaster University, Lancaster, United Kingdom A.Yu. Baikov Moscow University of Finance & Law, Moscow, Russia G. Burt Cockcroft Institute, Lancaster University, Lancaster, United Kingdom R.D. Kowalczyk L-3, Williamsport, Pennsylvania, USA I. Syratchev CERN, Geneva, Switzerland
	Future large-scale particle accelerators, for example, the Future Circular Collider (FCC), the Compact Linear Collider (CLIC) and the International Linear Collider (ILC), will require significant RF drive power on the order of 100 MW. Thus, an RF source with high efficiency is preferable to minimise the overall power required. Klystrons represent an attractive RF source, with the current state of the art operating at efficiencies of up to 70%. Such devices feature monotonic bunching, where at the output cavity, a number of electrons will not be in the main bunch, and instead will be present in the anti-bunch, and therefore not contributing to the output power. Therefore, novel bunching methods, such as the Core Oscillation Method (COM), are worthy of investigation. By allowing the core of the electron beam to bunch and de-bunch between successive cavities, the number of electrons contained in the final bunch can increase, and therefore improve the efficiency of the device. Numerical simulation of klystrons featuring COM will be presented, with efficiencies of up to 85% being predicted thus far.
	Slides MOOCA1 [12.765 MB]
DOI •	reference for this paper ※ https://doi.org/10.18429/JACoW-IPAC2017-MOOCA1
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MOPAB001	Status of the FCC-hh Collimation System	collimation, insertion, proton, collider	64
	J. Molson, A. Faus-Golfe LAL, Orsay, France R. Bruce, M. Fiascaris, A.M. Krainer, S. Redaelli CERN, Geneva, Switzerland
	Funding: Funding from the European Union's Horizon 2020 research and innovation programme under grant No 654305. The future circular hadron collider (FCC-hh) will have an unprecedented proton beam energy of 50 TeV, and total stored beam energy of 8.4 GJ. We discuss current developments in the collimation system design, and methods with which the challenges faced due to the high energies involved can be mitigated. Finally simulation results of new collimation system designs are presented.
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MOPAB003	Energy Deposition in the Betatron Collimation Insertion of the 100 TeV Future Circular Collider	dipole, insertion, proton, betatron	68
	M.I. Besana, C. Bahamonde Castro, A. Bertarelli, R. Bruce, F. Carra, F. Cerutti, A. Ferrari, M. Fiascaris, A. Lechner, A. Mereghetti, S. Redaelli, E. Skordis, V. Vlachoudis CERN, Geneva, Switzerland
	The FCC proton beam is designed to carry a total energy of about 8500 MJ, a factor of 20 above the LHC. In this context, the collimation system has to deal with extremely tight requirements to prevent quenches and material damage. A first layout of the betatron cleaning insertion was conceived, adapting the present LHC collimation system to the FCC lattice. A crucial ingredient to assess its performance, in particular to estimate the robustness of the protection devices and the load on the downstream elements, is represented by the simulation of the particle shower generated at the collimators, allowing detailed energy deposition estimations. This paper presents the first results of the simulation chain starting from the proton losses generated with the Sixtrack-FLUKA coupling, as currently done for the present LHC and for its upgrade. Expectations in terms of total power, peak power density and integrated dose on the different accelerator components are presented.
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MOPAB012	Study of the 2015 Top Energy LHC Collimation Quench Tests Through an Advanced Simulation Chain	ion, proton, collimation, heavy-ion	100
	E. Skordis, C.P. Welsch The University of Liverpool, Liverpool, United Kingdom R. Bruce, F. Cerutti, A. Ferrari, P.D. Hermes, A. Lechner, A. Mereghetti, S. Redaelli, B. Salvachua, E. Skordis, V. Vlachoudis CERN, Geneva, Switzerland C.P. Welsch Cockcroft Institute, Warrington, Cheshire, United Kingdom
	While the LHC has shown record-breaking perfor-mance during the 2016 run, our understanding of the behaviour of the machine must also reach new levels. The collimation system and especially the betatron cleaning insertion region (IR7), where most of the beam halo is intercepted to protect superconducting (SC) magnets from quenching, has so far met the expectations but could nonetheless pose a bottleneck for future operation at higher beam intensities for HL-LHC. A better under-standing of the collimation leakage to SC magnets is required in order to quantify potential limitations in terms of cleaning efficiency, ultimately optimising the collider capabilities. Particle tracking simulations com-bined with shower simulations represent a powerful tool for quantifying the power deposition in magnets next to the cleaning insertion. In this study, we benchmark the simulation models against beam loss monitor measure-ments from magnet quench tests (QT) with 6.5 TeV pro-ton and 6.37Z TeV Pb ion beams. In addition, we investi-gate the effect of possible imperfections on the collima-tion leakage and the power deposition in magnets.
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MOPAB013	Recent Development and Results With the Merlin Tracking Code	collimation, proton, collider, electron	104
	S.C. Tygier, R.B. Appleby, H. Rafique UMAN, Manchester, United Kingdom R.J. Barlow, S. Rowan IIAA, Huddersfield, United Kingdom J. Molson LAL, Orsay, France
	Funding: Work supported by High Luminosity LHC : UK (HL-LHC-UK), grant number ST/N001621/1 MERLIN is an high performance accelerator simulation code which is used for modelling the collimation system at the LHC. It is written in extensible object-oriented C++ so new physics processes can be easily added. In this article we present recent developments needed for the Hi-Lumi LHC and future high energy colliders including FCC, such as hollow electron lenses and composite materials. We also give an overview of recent simulation work, validation against LHC data from run 1 and 2, and loss maps for Hi-Lumi LHC.
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MOPAB014	Generating Low Beta Regions With Quadrupoles for Final Muon Cooling	emittance, quadrupole, collider, betatron	107
	J.G. Acosta, L.M. Cremaldi, T.L. Hart, S.J. Oliveros, D.J. Summers UMiss, University, Mississippi, USA D.V. Neuffer Fermilab, Batavia, Illinois, USA
	Funding: Work supported by Fermi Research Alliance, LLC under contract No. DE-AC02-07CH11359 Muon beams and colliders are rich sources of new physics, if muons can be cooled. A normalized rms transverse muon emittance of 280 microns has been achieved in simulation with short solenoids and a betatron function of 3 cm. Here we use ICOOL, G4beamline, and MAD-X to explore using a 400 MeV/c muon beam and strong focusing quadrupoles to approach a normalized transverse emittance of 100 microns and finish 6D muon cooling. The low beta regions produced by the quadrupoles are occupied by dense, low Z absorbers, such as lithium hydride or beryllium, that cool the beam. Equilibrium transverse emittance is linearly proportional to the beta function. Reverse emittance exchange with septa and/or wedges is then used to decrease transverse emittance from 100 to 25 microns at the expense of longitudinal emittance for a high energy lepton collider. Work remains to be done on chromaticity correction.
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MOPAB023	ESS Emittance Measurements at INFN CATANIA	emittance, ion, ion-source, proton	123
	O. Tuske, P. Daniel-Thomas, J.F. Denis, Y. Gauthier, T.J. Joannem, N. Misiara, V. Nadot, G. Perreu, F. Senée, V. Silva CEA/IRFU, Gif-sur-Yvette, France L. Celona, L. Neri INFN/LNS, Catania, Italy B. Cheymol, T.J. Shea ESS, Lund, Sweden I. Chu, M. Monteremand CEA LITEN, CEA Grenoble, Grenoble, France Ø. Midttun University of Bergen, Bergen, Norway T.V. Vacher CEA/DSM/IRFU, France
	Beam characteristics at low energy are an absolute necessity for an acceptable injection in the next stage of a linear accelerator, and are also necessary to reduce beam loss and radiation inside the machine. CEA is taking part of ESS linac construction, by designing Emittance Measurement Units (EMU) for the Low Energy Beam Transport (LEBT). The EMU are designed to qualify the proton beam produced by the INFN Catania ion source. This measurement has been decided to be time resolved, allowing to follow the beam emittance reduction, during the pulse length. A 1Mhz acquisition board controlled by EPICS save raw datas to an archiver in order to be able to post process the measurements for time resolution. The design corresponds to an Allison's scanner, using entrance and exit slits, electrostatic plates and a faraday cup. The beamstopper protects the device and can be removable to fit to beam power. It has been manufactured by the CEA/LITEN with copper tungsten HIP technique. This article report the first measurements on the ESS injector at INFN CATANIA.
DOI •	reference for this paper ※ https://doi.org/10.18429/JACoW-IPAC2017-MOPAB023
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MOPAB027	Preparation of CVD Diamond Detector for fast Luminosity Monitoring of SuperKEKB	luminosity, detector, monitoring, target	135
	C.G. Pang, P. Bambade, D. El Khechen, D. Jehanno, V. Kubytskyi, Y. Peinaud, C. Rimbault LAL, Orsay, France
	The SuperKEKB e⁺-e⁻ collider aims to reach a very high luminosity of 8×10 ³⁵ cm'2s'1, using highly focused ultra-low emittance bunches colliding every 4ns. To meet the requirement of the dithering feedback system used to stabilize the horizontal orbit at the IP (interaction point), a relative precision of 10 '3 in 1ms is specified for the fast luminosity monitoring, which can be in principle achieved thanks to the large cross section of the radiative Bhabha process. This paper firstly presents the fraction of detected Bhabha scattering positrons with a new beam pipe arrangement coupled with a Tungsten radiator to be installed in the Low Energy Ring; Then the characteristics of signals from a sCVD diamond detector with thickness of 140'm coupled with a broadband current amplifier were studied based on tests with a Sr-90 source; Finally, simulated results for the reconstructed luminosity and the relative precision with different assumed luminosities are also reported.
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MOPAB028	Estimation of Longitudinal Dimensions of Sub-Picosecond Electron Bunches with the 3-Phase Method	booster, electron, space-charge, gun	139
	H. Purwar, C. Bruni, A. Gonnin LAL, Orsay, France T. Vinatier DESY, Hamburg, Germany
	An estimation of the longitudinal dimensions for short electron bunches in an accelerating field is an important diagnostic and can be extremely helpful in evaluating the performance of an accelerator. We investigate a method for close estimation of bunch length for sub-picosecond electron bunches from the measurement of their energy spreads. Three or more measurements for the bunch energy spread are made by varying the phase of the accelerating structure and later a reconstruction of the bunch longitudinal dimensions, namely bunch length, initial energy spread and chirp at the entrance of the accelerating structure are obtained using the least square method. A comparison of the obtained results with ASTRA simulations is also included to validate the 3-phase method for sub-ps electron bunches. It is a simple method from both understanding (easy reconstruction using transport matrices) and experimental point of views (multiple measurements of energy spread with varying phase of the accelerating structure).
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MOPAB029	Experimental Study of Halo Formation at ATF2	vacuum, scattering, electron, detector	142
	R.J. Yang, P. Bambade, A. Faus-Golfe, V. Kubytskyi, S. Wallon LAL, Orsay, France A. Aryshev, T. Naito KEK, Ibaraki, Japan N. Fuster-Martínez IFIC, Valencia, Spain
	For Accelerator Test Facility 2 (ATF2), as well as other high-intensity accelerators, beam halo has been an important aspect reducing the machine performance and activating the components. It is imperative to clearly understand the mechanisms that lead to halo formation and to test the avail- able theoretical models with an adequate experiment setup. In this paper, the experimental measurement of the beam halo formation from beam gas scattering is presented. The upgrading of an OTR/YAG screen monitor for future halo study is also introduced.
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MOPAB037	Analytical and Numerical Performance Analysis of a Cryogenic Current Comparator	damping, cryogenics, dipole, beam-diagnostic	160
	N. Marsic, H. De Gersem, W.F.O. Müller TEMF, TU Darmstadt, Darmstadt, Germany F. Kurian, M. Schwickert, T. Sieber GSI, Darmstadt, Germany
	Funding: This research is funded by the German Bundesministerium für Bildung und Forschung as the project BMBF-05P15RDRBB Ultra-Sensitive Strahlstrommessung für zukünftige Beschleunigeranlagen. Nowadays, cryogenic current comparators (CCCs) are among the most accurate devices for measuring extremely small electric currents. Probably the most interesting property of this equipment, is the excellent position independence of the current passing through it. This feature motivated the use of CCCs for beam instrumentation in particle accelerators. A typical CCC consists of a ferrite core, a pick-up coil, a superconducting quantum interference device, appropriate electronics and superconducting shielding consisting of a meander structure. This configuration offers a strong attenuation for all the magnetic field components, except for the azimuthal one. Thus, high precision measurements of extremely low beam currents are made possible. The damping performance of this device is analysed in this work. A 3D finite element (FE) analysis has been carried out and the computed results were compared to an analytical model. Furthermore, in order to reduce the computation time, a 2.5D FE model is also proposed and discussed. K. Grohmann et al., Field attenuation as the underlying principle of cryo-current comparators 2. Ring cavity elements, Cryogenics, vol. 16, no. 10, pp. 601-605, 1976.
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MOPAB038	Research and Development of Diamond Based Beam Monitoring and Diagnostics Systems at the S-DALINAC	detector, monitoring, FPGA, electron	163
	A. Rost, T. Galatyuk TU Darmstadt, Darmstadt, Germany T. Galatyuk, J. Pietraszko GSI, Darmstadt, Germany
	Funding: This work has been supported by the DFG through GRK 2128 and VH-NG-823. For future experiments with the HADES and CBM detectors at FAIR in Darmstadt, a radiation hard and fast beam detector is required. The beam detector has to perform precise T0 measurements (σ_T0 < 50 ps) and should also offer beam monitoring capabilities. These tasks can be fulfilled by utilizing single-crystal Chemical Vapor Deposition (scCVD) diamond based detectors. For research and development of such detectors, a test set-up will be installed at the Superconducting Darmstadt Electron Linear Accelerator (S-DALINAC) of TU Darmstadt. A read-out system for a beam monitoring and diagnostics system is currently under development. It is based on the already well established TRB3 platform, which can provide FPGA based signal discriminators and high precision FPGA-TDCs with on-line monitoring capabilities. In this contribution the concept and the performance of a prototype beam monitoring system will be discussed. Furthermore the preparatory work, with particular focus on the beam-line simulations, for a multipurpose beam detector test set-up at the S-DALINAC will be addressed.
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MOPAB045	Reconstruction of the 3D Charge Distribution of an Electron Bunch Using a Novel Variable-Polarization Transverse Deflecting Structure (TDS)	electron, experiment, space-charge, laser	188
	D. Marx, R.W. Aßmann, U. Dorda, U. Dorda, B. Marchetti DESY, Hamburg, Germany P. Craievich PSI, Villigen PSI, Switzerland A. Grudiev, A. Grudiev, A. Grudiev CERN, Geneva, Switzerland
	A TDS is a well-known device for the characterization of the longitudinal properties of an electron bunch in a linear accelerator. So far, the correlation of the slice properties in the horizontal/vertical planes of the electron bunch distribution has been characterized by using a TDS system deflecting in the vertical/horizontal directions respectively and analysing the image on a subsequent screen. Recently, an innovative design for a TDS structure has been proposed, which includes the possibility of continuously varying the angle of the transverse streaking field inside a TDS structure. This allows the beam distribution to be characterized in all transverse directions. By collecting measurements of bunches streaked at different angles and combining them using tomographic techniques, it is possible to retrieve 3D distributions of the charge density. In this paper, a method is proposed and simulation results are presented to show the feasibility of such an approach at the upcoming accelerator R&D facility, SINBAD, at DESY*. M. Roehrs et al., Phys. Rev. ST Accel. Beams 12, 050704 (2009). A. Grudiev, Report No. CLIC-Note-1067, 2016. * B. Marchetti et al. X-band TDS project contribution to these conference proceedings.
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MOPAB048	Simulation of fs Bunch Length Determination with the 3-Phase Method and THz Dielectric Loaded Waveguides	injection, linac, space-charge, electron	199
	T. Vinatier, R.W. Aßmann, U. Dorda, B. Marchetti DESY, Hamburg, Germany
	In this paper, we investigate with ASTRA simulations the capability of the 3-phase method to reconstruct the length of a fs electron bunch. We show that a standard 3 GHz travelling wave accelerating structure is not suited for this purpose, because of the too important effect of the space-charge forces and of the too small variations of the induced energy spread with the bunch injection phase. Our simulations demonstrate that the use of dielectric-loaded waveguides driven by THz pulses would allow overcoming these two limitations and possibly achieving an ultimate resolution better than 5% for the determination of a 6.25 fs rms bunch length at 100 MeV energy and 1 pC charge. The next steps of the study to better evaluate, in simulations and experiments, the possible sources of degradation of the 3-phase method resolution are also mentioned.
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MOPAB052	A Transverse Deflection Structure with Dielectric-Lined Waveguides in the Sub-THz Regime	electron, emittance, impedance, laser	215
	F. Lemery University of Hamburg, Hamburg, Germany R.W. Aßmann, K. Flöttmann, T. Vinatier DESY, Hamburg, Germany
	Longitudinal bunch measurements are typically done with rf-powered transverse deflection structures with operating frequencies 1-12~GHz. We explore the use of mm-scale, THz-driven, dielectric-lined cylindrical waveguides as transverse deflectors by driving the fundamental deflecting mode of the structure, the HEM₁₁. We give a brief overview of the physics, history, and provide an example with a 5~MeV beam using {\sc astra} and {\sc CST-MWS}. This work was supported by the European Research Council (ERC) under the European Union's Seventh Framework Programme (FP/2007-2013)/ERC Grant agreement no. 609920
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MOPAB053	Electron Bunch Streaking With Single-Cycle THz Radiation Using an NSOM-Style TIP	electron, laser, interaction-region, diagnostics	219
	F. Lemery, A.F. Hartin University of Hamburg, Hamburg, Germany D. Zhang DESY, Hamburg, Germany D. Zhang CFEL, Hamburg, Germany
	THz wavelengths provide an excellent scale for electron-bunch acceleration and manipulation. The improvement of laser-based THz-generation efficiencies to ~1% provides a good opportunity for e.g. phase-space manipulation and diagnostics. We describe a simple technique to streak and characterize electron beams. We provide full simulation results and discuss the scaling of this technique to various regimes.
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MOPAB054	Development and Application of Rogowski Coils as Beam Position Monitors	dipole, storage-ring, instrumentation, synchrotron	223
	F. Trinkel, H. Soltner FZJ, Jülich, Germany
	We have developed segmented Rogowski coils as a beam position monitors at the storage ring COSY Jülich as an alternative to the conventional monitors installed there. These coils feature a torus with two or four segments, each densely covered with an insulating copper wire of 150μm in diameter. The bunched particle beam induces voltages in these segments, which are combined and analysed to yield information about beam displacements in the horizontal and the vertical plane. We highlight our theoretical understanding of position determination of these coils together with corresponding numerical simulations. The integration of such a beam position monitor with COSY and first results with it for a bunched deuteron beam are described. The ultimate goal of this development is a better control of the beam orbit for the very demanding requirements in a future ring dedicated to the measurement of Electric Dipole Moments (EDMs) of charged particles.
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MOPAB056	4-Channel Single Shot and Turn-by-Turn Spectral Measurements of Bursting CSR	detector, radiation, synchrotron, storage-ring	231
	J.L. Steinmann, E. Blomley, M. Brosi, E. Bründermann, M. Caselle, B. Kehrer, A.-S. Müller, L. Rota, M. Schuh, P. Schönfeldt, M. Siegel, M. Weber KIT, Karlsruhe, Germany
	The test facility and synchrotron radiation source ANKA at the Karlsruhe Institute of Technology (KIT) in Karlsruhe, Germany, can be operated in a short-bunch mode. Above a threshold current, the high charge density leads to microwave instabilities and the formation of sub-structures. These time-varying sub-structures on bunches of picosecond duration lead to the observation of bursting coherent synchrotron radiation (CSR) in the terahertz (THz) frequency range. The spectral information in this range contains valuable information about the bunch length, shape and sub-structures. We present recent measurements of a spectrometer setup that consists of 4 ultra-fast THz detectors, sensitive in different frequency bands, combined with the KAPTURE readout system developed at KIT for studies requiring high data throughput. This setup allows to record continuously the spectral information on a bunch-by-bunch and turn-by-turn basis. This contribution describes the potential of time-resolved spectral measurements of the short-bunch beam dynamics.
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MOPAB059	Energy Chirp Measurements by Means of an RF Deflector: a Case Study the Gamma Beam Source LINAC at ELI-NP	electron, linac, brightness, detector	242
	L. Sabato U. Sannio, Benevento, Italy P. Arpaia, A. Liccardo Naples University Federico II, Science and Technology Pole, Napoli, Italy A. Mostacci, L. Palumbo University of Rome La Sapienza, Rome, Italy A. Variola INFN/LNF, Frascati (Roma), Italy
	RF Deflector (RFD) based measurements are widely used in high–brightness electron LINAC around the world in order to measure the ultra–short electron bunch length. The RFD provides a vertical kick to the particles of the electron bunch according to their longitudinal positions. In this paper, a measurement technique for the bunch length and other bunch proprieties, based on the usage of an RFD, is proposed. The basic idea is to obtain information about the bunch length, energy chirp, and energy spread from vertical spot size measurements varying the RFD phase, because they add contributions on this quantity. The case study is the Gamma Beam System (GBS), the Compton Source being built in the Extreme Light Infrastructure–Nuclear Physics (ELI–NP) facility. The ELEctron Generation ANd Tracking (ELEGANT) code is used for tracking the particles from RFD to the measurement screen.
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MOPAB060	Thermal Issues for the Optical Transition Radiation Screen for the ELI-NP Compton Gamma Source	electron, target, radiation, laser	246
	F. Cioeta, D. Alesini, A. Falone, V.L. Lollo, L. Pellegrino, A. Variola INFN/LNF, Frascati (Roma), Italy M. Ciambrella University of Rome La Sapienza, Rome, Italy D. Cortis, M. Marongiu, V. Pettinacci INFN-Roma, Roma, Italy A. Mostacci, L. Palumbo Rome University La Sapienza, Roma, Italy
	A high brightness electron Linac is being built in the Compton Gamma Source at the ELI Nuclear Physics facility in Romania. To achieve the design luminosity, a train of 32 bunches, 16 ns spaced, with a nominal charge of 250 pC will collide with the laser beam in two interaction points. Electron beam spot size is measured with optical transition radiation (OTR) profile monitors. In order to measure the beam properties, the OTR screens must sustain the thermal and mechanical stress due to the energy deposited by the bunches. This paper is an ANSYS study of the issues due to the high energy transferred to the OTR screens. Thermal multicycle analysis will be shown; each analysis will be followed by a structural analysis in order to investigate the performance of the material. The multiphysics analysis will be extended to the mechanical contact areas with the target frame in order to evaluate the order of magnitude of the phenomena in those regions.
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MOPAB064	Photoinjector Emittance Measurement at STAR	emittance, gun, electron, solenoid	257
	A. Bacci, C. Curatolo, I. Drebot, L. Serafini, V. Torri Istituto Nazionale di Fisica Nucleare, Milano, Italy R.G. Agostino, R. Barberi, V. Formoso, M. Ghedini, F. Martire, C. Pace UNICAL, Arcavacata di Rende, Italy D. Alesini, M. Bellaveglia, J.J. Beltrano, F.G. Bisesto, G. Borgese, B. Buonomo, G. Di Pirro, G. Di Raddo, A. Esposito, A. Gallo, A. Ghigo, F. Iungo, A. Papa, L. Pellegrino, A. Stella, C. Vaccarezza, S. Vescovi INFN/LNF, Frascati (Roma), Italy A. Cianchi Università di Roma II Tor Vergata, Roma, Italy G. D'Auria, A. Fabris, M. Marazzi Elettra-Sincrotrone Trieste S.C.p.A., Basovizza, Italy V. Petrillo Universita' degli Studi di Milano, Milano, Italy A. Policicchio UniCal & INFN CS, Arcavacata di Rende (CS), Italy E. Puppin Politecnico/Milano, Milano, Italy M. Rossetti Conti Universita' degli Studi di Milano & INFN, Milano, Italy
	STAR is an advanced Thomson source of monochromatic and tunable, ps-long, polarised X-ray beams in the 40-140 keV range. The commissioning has started at the Univ. of Calabria (Italy). The light source is driven by a high-brightness, low-emittance electron beam produced in a LINAC allowing for the source tunability and spectral density. This note reports on an emittance measurement schema based on the insertion of a slit mask in the vacuum chamber dedicated to the photocathode laser entrance. Results of the simulation of the measurement technique are reported, and the use of the data for the optimisation of the accelerator performance are detailed. The experimental setup and the application developed in EPICS for image recording and analysis are also described.
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MOPAB066	Development and Performance Test of the BPM System for the SPring-8 Upgrade	radiation, storage-ring, electron, photon	265
	H. Maesaka RIKEN SPring-8 Center, Innovative Light Sources Division, Hyogo, Japan H. Dewa, T. Fujita, M. Masaki JASRI, Hyogo, Japan S. Takano Japan Synchrotron Radiation Research Institute (JASRI), RIKEN SPring-8 Center, Hyogo, Japan
	We are developing a stable and precise BPM system for the low-emittance upgrade of SPring-8. One of the essential requirements for the BPM is the long term stabilization of the photon beam by regulating the electron beam orbit. Both the single-pass resolution of 100 um rms for an injected beam charge of 100 pC and an accuracy of 100 um rms are also crucial for beam commissioning. Drift sources of the present BPM system have been investigated extensively, such as humidity-dependent drifts coming from the radiation damage of coaxial cables, and the results are fed back to the design of the new BPM system. We have optimized the design of the button BPM electrodes to reconcile reduction of trapped-mode heating and maximization of the signal intensity. Stringent machining tolerance is imposed on a BPM head to align the BPM electric center accurately. A few kinds of the BPM head prototypes were produced and the machining accuracy, RF characteristics etc. were confirmed to be sufficient. We have installed one of the prototypes in the present storage ring to test the performance of the new BPM system under development, and have been obtaining successful results satisfying the requirements.
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MOPAB069	Measurement of Transverse Multipole Moments of the Proton Beam in the J-PARC MR	quadrupole, multipole, proton, vacuum	274
	T. Toyama J-PARC, KEK & JAEA, Ibaraki-ken, Japan A. Ichikawa, A. Minamino, K.G. Nakamura, Y. Nakanishi, T. Nakaya, W. Uno Kyoto University, Kyoto, Japan T. Koseki, H. Kuboki, M. Okada KEK, Tokai, Ibaraki, Japan
	Funding: This work was partially supported by MEXT/JSPS KAKENHI Grant Numbers 25105002 and 16H06288. Transverse multipole moments (quadrupole and more) of the beam may give important informations of the beam such as beam sizes, nonlinear resonances and so on. However higher moments are difficult to measure because signal-to-noise-ratio becomes smaller proportional to the n-th order of the beam-radius-to-vacuum-duct-radius ratio. In order to increase the SNR and to extend the multipole order, we developed and installed a 16 electrode beam monitor in the J-PARC MR, which consists of guard-potential-separated 16 striplines. The calibration method, beam test results will be presented.
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MOPAB082	Design and Simulation of High Order Mode Cavity Bunch Length Monitor for Infrared Free Electron Laser	cavity, FEL, laser, electron	309
	Q. Wang, X.Y. Liu, P. Lu, Q. Luo, B.G. Sun, L.L. Tang, J.H. Wei, F.F. Wu, Y.L. Yang, T.Y. Zhou, Z.R. Zhou USTC/NSRL, Hefei, Anhui, People's Republic of China
	Funding: Supported by The National Key Research and Development Program of China (2016YFA0401900, 2016YFA0401903); NSFC (11375178, 11575181); the Fundamental Research Funds for the Central Universities (WK2310000046) A bunch length monitor using resonant cavity has been designed for the NSRL Infrared Free Electron Laser (IR-FEL) facility. To avoid the restriction of working fre-quency caused by the beam pipe radius, the high order modes of the harmonic cavities are utilized. The position and orientation of coaxial probes are optimized to avoid interference modes which come from the cavity and beam tube according to the analysis formula of electro-magnetic field distribution. Based on the parameters of IR-FEL, a simulation is performed to verify the feasibility of the bunch length monitor. The simulation result shows that the design meets the requirements of IR-FEL, and the resolution can be better than 50 fs.
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MOPAB087	Study on Supports System of BPMs for HEPs	site, factory, storage-ring, synchrotron	322
	Z.Z. Wang, J.S. Cao, J. He, H.Z. Ma, Y.F. Sui, Z. Wang IHEP, People's Republic of China
	The High Energy Photon Source(HEPS), a third generation light source with the energy of 6 GeV, is under constructed at IHEP. It has an ultralow emittance (~50pm.rad) and small beam size, thus the requirement of BPM in precision and resolution is quite high. Independent supports with high degree of mechanical and thermal stability will be employed for some special BPMs, such as the BPMs near the insert devices. The supports should have high eigen-frequencies to minimize the amplification of vibration from the ground. Vibrations information of the ground around the supports also need be estimated, with which FEA (finite element analysis) had be utilized to simulate the performance of the supports. Measurements of vibrational stability of the prototype supports have be done and compared with the simulation.
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MOPAB088	A Differential Beam Intensity Monitoring for the CIADS LINAC	monitoring, linac, instrumentation, pick-up	325
	Z.P. Xie Hohai University, Nanjing, People's Republic of China Y. He, R. Huang, Z.J. Wang IMP/CAS, Lanzhou, People's Republic of China
	Funding: Work supported by the National Natural Science Foundation of China (Grant No. 91026001) and the Fundamental Research Funds for the Chinese Central Universities The high power Linac places many crucial requirements on the beam diagnostics for the China initiative accelerator driven subcritical(CIADS) facility. Measuring the beam loss is essential for the purpose of machine protections for the facility. A beam position pickup based differential beam current monitoring (BPDBCM) scheme has been proposed for the MEBT section at CIADS. Discussions of the principles for the scheme and the realtionship between beam intensity measurement and the pulse length are presented. Simulations are performed and they demonstrate that the proposed system can be effective at the low enery section for the CIADS beam. This paper describes the proposed implementation that will have the capability of detecting both the instantaneous and chronicle loss in real time.
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MOPAB090	Wavefront Distortion Measurement at SSRF	experiment, radiation, synchrotron, synchrotron-radiation	332
	B. Gao, H.J. Chen, J. Chen, Y.B. Leng, K.R. Ye SINAP, Shanghai, People's Republic of China B. Gao University of Chinese Academy of Sciences, Beijing, People's Republic of China N. Zhang SSRF, Shanghai, People's Republic of China
	The Synchrotron Radiation Monitor (SRM) system has been designed and constructed at the Shanghai synchrotron radiation Facility (SSRF) for several years and runs good. However, the monitor extraction mirror deformation is quite common at different facilities, and other reflecting mirrors in the optic path also have surface error and angle error. As we decide to upgrade the SR monitor system at SSRF, this issue is also one of the most import thing what we should overcome. In order to verify the feasibility and evaluate the accuracy, simulations based on SRW code have been done. In this simulation, a dedicated algorithm was developed to reconstruct wavefront. The result and the algorithm is very useful for our experiment and upgrade program. In this paper, the algorithm and the experiments based on Shark-Hartmann wavefront sensor will be presented detailed.
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MOPAB093	Bunch Phase Measurement for Storage Ring	storage-ring, injection, experiment, pick-up	341
	Y.M. Zhou, Y.B. Leng, N. Zhang SSRF, Shanghai, People's Republic of China H.J. Chen SINAP, Shanghai, People's Republic of China
	A bunch-by-bunch phase measurement system has been studied to improve the accuracy of phase measurement. Longitudinal phase information will be retrieved from beam signals picked up from the button electrodes. The signals from four electrodes in the BPM are summed by using a 4-way power driver, by which the effect of the transverse beam offset on the phase measurement can be eliminated. Four samples with fixed time interval (typical 100ps) for each bunch, which are taken by a 500MHz waveform recorder with a four channels signal splitting and delaying network, will be used to calculate bunch phase. In this paper, we present the layout of the system and primary experimental results.
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MOPAB095	Development of the Simulation Software Package for the CBPM System	cavity, network, FEL, experiment	349
	J. Chen, L.W. Lai, Y.B. Leng, L.Y. Yu SINAP, Shanghai, People's Republic of China N. Zhang SSRF, Shanghai, People's Republic of China
	In recent years, the development and construction of Free Electron Laser (FEL) facilities are in full swing. For FEL facilities, to generate coherent X-ray, cavity beam position monitor (CBPM) system which consist of cavity BPM, RF front-end and signal processor are employed to measure the transverse position in the undulator section. A generic simulation software package, with the S21 parameters of the real components, for the design of the RF front-end and the optimize of the CBPM system was developed. In this paper, the development of the generic simulation software package, and the experiment results with beam at Shanghai Deep ultraviolet (SDUV) FEL facility to verify the correctness of the simulation soft package will be introduced. The application in the design and optimize of the RF front-end for the Dalian Coherent Source (DCLS) will be addressed as well .
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MOPAB099	Design Study of Drift Tube Linac for BNCT Accelerator	DTL, quadrupole, rfq, linac	359
	Y. Lee, S.W. Jang, E.-S. Kim Korea University Sejong Campus, Sejong, Republic of Korea B.H. Choi IBS, Daejeon, Republic of Korea D.S. Kim Dawonsys, Siheung-City, Republic of Korea Z. Li SCU, Chengdu, People's Republic of China
	A-BNCT accelerator is being developed as a proton accelerator with a high beam current of 50 mA for effective cancer therapy. Drift tube linac (DTL) with the length of 4.5 m is composed of 1 tank and 48 drift tubes (DTs). Proton beam is accelerated from 3 MeV to 10 MeV. Electromagnetic quadrupoles (EMQs) are inserted into every DT for transverse focusing. Slug tuners and post couplers (PCs) are used for accelerating field stabilization and resonant frequency tuning, respectively. The beam dynamics and engineering design for the DTL are performed for effective beam acceleration, and the design results are in detail presented.
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MOPAB107	A Method for Determining the Roll Angle of the CLIC Accelerating Structures From the Beam Shape Downstream of the Structure	octupole, collider, experiment, emittance	368
	J. Ögren, V.G. Ziemann Uppsala University, Uppsala, Sweden W. Farabolini CEA/DSM/IRFU, France
	The Compact Linear Collider (CLIC) accelerating structures have a four-fold symmetry from the radial waveguides for damping higher order modes. This symmetry allows for an octupole component of the rf fields to co-propagate with the main accelerating field. The effect of this octupole mode has been observed at the CLIC test facility 3. In CLIC the accelerating structures are mounted together on a moveable girders. There are four vertical and four horizontal actuators on the girder, which allows for 5D control in a limited range and for instance we can roll the girder. By observing the beam shape perturbed by the octupole field on a screen downstream from the structure we can determine the roll angle and thus align the structure azimuthally. Here we discuss a possible method and show some preliminary results.
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MOPAB109	Operational Experience with Luminosity Scans for Beam Size Estimation in 2016 LHC Proton Physics Operation	emittance, luminosity, operation, proton	374
	M. Hostettler LHEP, Bern, Switzerland K. Fuchsberger, G. Papotti CERN, Geneva, Switzerland
	Luminosity scans were regularly performed at the CERN Large Hadron Collider (LHC) as of 2015 as a complementary method for measuring the beam size. The CMS experiment provides bunch-by-bunch luminosities at sufficient rates to allow evaluation of bunch-by-bunch beam sizes, and the scans are performed in the horizontal and vertical plane separately. Closed orbit differences between bunches can also be derived by this analysis. During 2016 LHC operation, these scans were also done in an automated manner on a regular basis, and the analysis was improved to significantly reduce the systematic uncertainty, especially in the crossing plane. This contribution first highlights the recent improvements to the analysis and elaborates on their impact. The measured beam sizes during 2016 proton physics operation are then shown and compared to measurements from synchrotron light telescopes and estimates based on the absolute luminosities of the LHC experiments.
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MOPAB111	Diffraction Radiation for Non-Invasive, High-Resolution Beam Size Measurements in Future Linear Colliders	target, radiation, collider, polarization	381
	M. Bergamaschi, R. Kieffer, T. Lefèvre, S. Mazzoni CERN, Geneva, Switzerland A. Aryshev, N. Terunuma KEK, Ibaraki, Japan M. Bergamaschi, P. Karataev, K.O. Kruchinin JAI, Egham, Surrey, United Kingdom M. Bergamaschi, P. Karataev, K.O. Kruchinin Royal Holloway, University of London, Surrey, United Kingdom
	Next generation linear colliders such as the Compact Linear Collider (CLIC) or the International Linear Collider (ILC) will accelerate particle beams with extremely small emittance. The high current and small size of the beam (micron-scale) due to such small emittance require non-invasive, high-resolution techniques for beam diagnostics. Diffraction Radiation (DR), a polarization radiation that appears when a charged particle moves in the vicinity of a medium, is an ideal candidate being non-invasive and allowing beams as small as a few tens of microns to be measured. Since DR is sensitive to beam parameters other than the transverse profile (e.g. its divergence and position), preparatory simulations have been performed with realistic beam parameters. A new dedicated instrument was installed in the KEK-ATF2 beam line in February 2016. At present DR is observed in the visible wavelength range, with an upgrade to the ultraviolet (200nm) planned for spring 2017 to optimize sensitivity to smaller beam sizes. Presented here are the latest results of these DR beam size measurements and simulations.
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MOPAB127	A New Method for Emittance Reconstruction Using a Scraper in a Dispersive Region of a Low Energy Storage Ring	emittance, storage-ring, antiproton, closed-orbit	429
	J.R. Hunt, J. Resta-López, C.P. Welsch The University of Liverpool, Liverpool, United Kingdom C. Carli CERN, Geneva, Switzerland J.R. Hunt, J. Resta-López, C.P. Welsch Cockcroft Institute, Warrington, Cheshire, United Kingdom
	Funding: Science and Technology Funding Council, UK CERN Beam scraping is a standard method for beam emittance measurements at low energies and will be applied at the Extra Low ENergy Antimatter (ELENA) ring. However, in ELENA, as in many other low energy storage rings, the scraper is located in a position of finite dispersion which poses a unique challenge when reconstructing the emittance from beam intensity data. A new algorithm for ELENA and other machines that use a scraper in a dispersive region has been developed. It combines data obtained by scraping the beam from opposite sides with information on the storage ring lattice. In this contribution, the new algorithm is presented, tested using simulations and compared with alternate methods for emittance reconstruction.
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MOPAB137	Validation of a Novel Emittance Diagnostic Method for Beams with Significant Space Charge	emittance, space-charge, focusing, quadrupole	451
	R.B. Fiorito, C.P. Welsch, H.D. Zhang Cockcroft Institute, Warrington, Cheshire, United Kingdom M.E. Conde, N.R. Neveu, J.F. Power ANL, Argonne, Illinois, USA O. Mete Apsimon Cockcroft Institute, Lancaster University, Lancaster, United Kingdom A.G. Shkvarunets UMD, College Park, Maryland, USA
	Funding: Work supported by the EU under grant agreement 624890, the STFC Cockcroft Institute Core Grant No. ST/G008248/1. Exact knowledge of beam emittance is of central importance for essentially every accelerator. However, there are only few methods to determine it when the beam has significant space charge. We report on our progress to validate a novel diagnostic method that has been proposed to determine the RMS emittance of an electron beam with space charge. This method uses RMS divergence and beam size data measured at a screen placed in a free drift region for selected values of magnetic focusing strength. A novel algorithm is then used to determine the cross correlation term and consequently the RMS emittance of the beam. Simulations, quadrupole scans, phase space tomography and optical diffraction-dielectric foil radiation interferometry are currently being employed to determine and compare the horizontal (x) and vertical (y) emittances of the 14 MeV witness electron beam at Argonne National Laboratory's Wakefield Accelerator. The results of simulations and current measurements are presented and the advantages of the new technique are discussed.
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MOPAB138	Comparison of Optical Transition Radiation Simulations and Theory	radiation, diagnostics, optics, electron	455
	J. Wolfenden, R.B. Fiorito, C.P. Welsch Cockcroft Institute, Warrington, Cheshire, United Kingdom M. Bergamaschi, P. Karataev, K.O. Kruchinin JAI, Egham, Surrey, United Kingdom M. Bergamaschi, P. Karataev, K.O. Kruchinin Royal Holloway, University of London, Surrey, United Kingdom M. Bergamaschi, R. Kieffer, T. Lefèvre CERN, Geneva, Switzerland R.B. Fiorito, C.P. Welsch, J. Wolfenden The University of Liverpool, Liverpool, United Kingdom
	The majority of optical diagnostics currently used will not stand up to the requirements of the next generation of particle accelerators. Current methodologies need innovation to be able to reach the sub-micrometre resolution and sensitivity that will be required. One technique that has the potential to meet these requirements is optical transition radiation (OTR) imaging. A new algorithm is proposed which incorporates OTR theory, optical effects and beam distribution. This algorithm takes an existing method used for beam imaging and pushes the limits resolution beyond that normally attainable. In doing so, it can provide a reliable and economical diagnostic for future accelerators. A discussion on further applications of the algorithm is also presented.
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MOPAB141	Instrumentation and Its Interaction With the Secondary Beam for the Fermilab Muon Campus	ion, experiment, vacuum, emittance	466
	D. Stratakis, B.E. Drendel, M.J. Syphers Fermilab, Batavia, Illinois, USA M.J. Syphers Northern Illinois University, DeKalb, Illinois, USA
	Funding: Operated by Fermi Research Alliance, LLC under Contract No. De-AC02-07CH11359 with the United States Department of Energy. The Fermilab Muon Campus will host the Muon g-2 experiment - a world class experiment dedicated to the search for signals of new physics. Strict demands are placed on the beam diagnostics in order to ensure delivery of high quality beams to the storage ring with minimal losses. In this study, we briefly describe the available secondary beam diagnostics for the Fermilab Muon Campus. Then, with the aid of numerical simulations we detail their interaction with the secondary beam. Finally, we compare our results against theoretical findings.
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MOPIK006	Characterization of the Electron Beam from the Thz Driven Gun for AXSIS	electron, gun, experiment, diagnostics	509
	G. Vashchenko, R.W. Aßmann, U. Dorda, K. Galaydych, B. Marchetti, T. Vinatier DESY, Hamburg, Germany M. Fakhari, A. Fallahi, F.X. Kärtner, N.H. Matlis CFEL, Hamburg, Germany W. Qiao, C. Zhou University of Hamburg, Hamburg, Germany
	Funding: The research leading to these results has received funding from the European Research Council under the European Union's Seventh Framework Programme (FP/2007-2013) / ERC Grant Agreement n. 609920 The AXSIS (Attosecond X-ray Science: Imaging and Spectroscopy) project aims for development of a compact, fully coherent, THz-driven, attosecond X-ray source. A compact THz driven gun was developed, produced and tested as a source of the ultra-short electron bunches required for the project. To characterize the low energy, low-charge beam produced by such a gun tailored diagnostic devices were developed and commissioned at a test-stand chamber in CFEL (DESY). Results of the first experiments on the production and characterization of the electron beam are presented.
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MOPIK008	Numerical Studies on a Modified Cathode Tip for the ELBE Superconducting RF Gun	electron, cathode, SRF, gun	515
	E.T. Tulu, U. van Rienen Rostock University, Faculty of Computer Science and Electrical Engineering, Rostock, Germany A. Arnold HZDR, Dresden, Germany
	Future light sources such as synchrotron radiation sources driven by an Energy Recovery Linac (ERL), Free Electron Laser (FEL) or THz radiation sources have in common that they require injectors, which provide high-brilliance, high-current electron beams in almost continuous operation. Thus, the development of appropriate highly brilliant electron sources is a central factor. A promising approach for this key component is provided by superconducting radiofrequency photoinjectors (SRF guns) []. Since 2007, the free-electron laser FELBE at HZDR successfully operates such a SRF gun under real conditions and equipped with all components []. Nevertheless, there are limitations caused by multipacting which should be overcome in order to further improve the gun []. One aspect in order to reach this aim lies in studying various modifications of the cathode tip [*]. This contribution will present the effectiveness of isosceles triangular grooves with respect to MP. Arnold, et al., NIM A, 593, 57, (2008). J. Teichert, et al., 2008 NSS/MIC, Dresden, Germany. * J. Teichert, et al., J. Phys.: Conf. Ser. 298(2011), 012008. **** E. T. Tulu, et al., IPAC2014, p652, Dresden, Germany.
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MOPIK009	Characterization of Cold Model Cavity for Cryocooled C-Band 2.6-Cell Photocathode RF Gun at 20 K	cavity, gun, experiment, cryogenics	518
	T. Tanaka, K. Hayakawa, Y. Hayakawa, K. Nakao, K. Nogami, T. Sakai, K. Takatsuka LEBRA, Funabashi, Japan M.K. Fukuda, D. Satoh, T. Takatomi, N. Terunuma, J. Urakawa, M. Yoshida KEK, Ibaraki, Japan
	Funding: This work was partly supported by the Photon and Quantum Basic Research Coordinated Development Program of the Japanese Ministry of Education, Culture, Sports, Science, and Technology (MEXT). A cryocooled C-band 2.6-cell photocathode RF electron gun has been studied at Nihon University in cooperation with KEK. The cold model cavity with an input coupler was completed in spring 2016. The RF characteristics measured at room temperature were in agreement with the prediction by the CST Studio simulation. The RF characteristics at 20 K have been measured using a rather simple cavity-cooling vacuum system that was built by using existing components for tentative experiments. A thin-wall stainless-steel R48 waveguide with copper-plated inner walls has been used for the RF power transmission from the room-temperature input port to the 20-K cooled coupler waveguide. The unloaded Q-value of 73000 has been obtained by the reflection coefficient measurement at 20 K, which is in agreement with the result of the CST Studio simulation using the cavity surface resistance predicted by the theory of the anomalous skin effect.
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MOPIK016	Sub-Picosecond Beam Production for External Injection Into Plasma Experiments	gun, plasma, electron, linac	531
	O. Mete Apsimon, R. Apsimon, G. Burt Cockcroft Institute, Lancaster University, Lancaster, United Kingdom G.X. Xia UMAN, Manchester, United Kingdom
	Funding: This work has been funded by STFC. Applications of plasmas in accelerators benefit from short probe bunches comparable to plasma wavelength due to currently achievable plasma wake profiles. In plasma acceleration case, high capture efficiency within a narrow energy spectrum can be achieved when a sub-picosecond to femtosecond witness bunch injected behind the driver pulse at the high electric field region. A start-to-end simulation study was performed for parametric optimisation of an rf photoinjector to provide a short witness bunch for plasma applications in accelerators. An rf photoinjector is a laser-driven, high brightness and robust electron source that can provide stability and flexibility provided by today's advanced laser and rf technologies.
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MOPIK021	Generation of Transversely Segmented Beam Using a Nano-Patterned Photocathode	cathode, laser, gun, acceleration	545
	A. Lueangaramwong, P. Piot Northern Illinois University, DeKalb, Illinois, USA G. Andonian RadiaBeam, Santa Monica, California, USA P. Piot Fermilab, Batavia, Illinois, USA
	Funding: Work supported by US Department of Energy (DOE) contract DE-SC0009656 with Radiabeam Technologies and by NSF grant PHY-1535401 with Northern Illinois University. Plasmonic photocathodes – nano-patterned photocathodes with periodicity comparable to the excitation laser – have demonstrated enhanced quantum efficiency. In the present paper we present numerical simulations of the beam dynamics associated to the emission process from this type of cathodes and to the subsequent acceleration to relativistic energies by combining WARP and IMPACT-T programs. We especially consider the possibility to transversely image the cathode surface at high energy and enable the generation of transversely segment beams.
DOI •	reference for this paper ※ https://doi.org/10.18429/JACoW-IPAC2017-MOPIK021
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MOPIK023	Cornell Laboratory for High Intensity, Ultra-Bright and Polarized Electron Beams	electron, gun, cathode, ion	551
	L. Cultrera, A.C. Bartnik, I.V. Bazarov, C.M. Gulliford, P. Gupta, H. Lee, S.A. McBride, T.P. Moore Cornell University (CLASSE), Cornell Laboratory for Accelerator-Based Sciences and Education, Ithaca, New York, USA
	Funding: This work has been funded by the National Science Foundation (Grant No. PHY-1416318) and Department of Energy (Grants No. DE-SC0014338, No. DE-SC0011643 and No. DE-SC0016203). We report on the current activities pursued at Cornell University for the production of electron beams tailored to a wide range of applications. We have developed the expertise to grow many different type of high quantum efficiency photocathode belonging to the alkali antimonide family. Those materials are ideal candidates to produce high intensity beam with average currents in the mA range. When operated near threshold at cryogenic temperature in transmission mode they can also generate the electron beams needed to perform ultrafast electron diffraction of bio molecules. We have recently expanded our facility with a Mott polarimeter to include the capability to measure polarization of the electron beam. The photocathode lab is being complemented by a dedicated photo-gun laboratory to test the photocathode properties in a real environment and to perform measurement of the beam properties under new and yet unexplored operating conditions.
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MOPIK028	Simulation Study of Halo Collimation in the TRIUMF Ariel Proton Beam Line	proton, collimation, scattering, cyclotron	557
	F.W. Jones, R.A. Baartman, I.V. Bylinskii, Y.-N. Rao TRIUMF, Vancouver, Canada
	Funding: Funded under a contribution agreement with NRC (National Research Council of Canada). Capital funding from CFI (Canada Foundation for Innovation). The TRIUMF 500 MeV H⁻ cyclotron uses stripping foil extraction to drive several proton beam lines serving different experimental programs. As part of TRIUMF's Ariel facility now under construction, a new proton beam line 4-North will be installed to transport up to 100 microamps of 480 MeV protons to an ISOL target station for rare isotope beam production. This beam line has been designed for low-loss (< 1nA/m) operation and provides space for a collimator to remove the beam halo produced by large-angle scattering in the cyclotron extraction foil. We have studied proton loss patterns and collimation efficiency using simulation codes: the older REVMOC program and a fully 3D simulation based on Geant4, with all particle interactions in matter included. Scattering in the foil is treated by a separate iterated single-scatter model. Using these tools we arrive at a prototype design for an effective collimator.
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MOPIK039	Transport Channel of Secondary Ion Beam of Experimental Setup for Selective Laser Ionization With Gas Cell Gals	ion, quadrupole, target, neutron	589
	N.Yu. Kazarinov, V. Bashevoy, G.G. Gulbekyan, I.A. Ivanenko, V.I. Kazacha, N.F. Osipov JINR, Dubna, Moscow Region, Russia S.G. Zemlyanoy JINR/FLNR, Moscow region, Russia
	GALS is the experimental setup intended for production and research of isobaric- and isotopically pure heavy neutron-rich nuclei. The beam line consists of two parts. The initial part is used for transport of the primary 136Xe ion beam with energy of 4.5-9.0 MeV/amu from the FLNR cyclotron U400M to the Pb target for the production of the studying ion beams. These beams have the following design parameters: the charge Z = +1, the mass A = 180-270 and the kinetic energy W = 40 keV. The second part placed after the target consists of SPIG (QPIG) system, the accelerating gap, the electrostatic Einzel lens, 90-degree spectrometric magnet (calculated value of the mass-resolution is equal to 1400) and the channel for the transportation of the ions from the focal plane of the magnet to a particle detector. The results of the simulation of particle dynamics and the basic parameters of the elements of the beam lines are presented in this report.
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MOPIK044	The Use of a Passive Scatterer for SPS Slow Extraction Beam Loss Reduction	scattering, extraction, septum, proton	607
	B. Goddard, B. Balhan, J.C.C.M. Borburgh, M.A. Fraser, L.S. Stoel, F.M. Velotti CERN, Geneva, Switzerland
	A significant reduction in the fraction of protons lost on the SPS electrostatic septum ES during resonant slow extraction is highly desirable for present Fixed-Target beam operation, and will become mandatory for the proposed SHiP experiment, which is now being studied in the framework of CERN's Physics Beyond Colliders program. In this paper the possible use of a passive scattering device (diffuser) is investigated. The physics processes underlying the use of a diffuser are described, and the dependence on the diffuser geometry, material and location of the potential loss reduction on the electrostatic septum (ES) wires is investigated with a semi-analytical approach. Numerical simulations to quantify the expected performance gain for the optimum configuration are presented, and the results discussed in view of the feasibility of a potential realisation in the SPS.
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MOPIK045	SPS Slow Extraction Losses and Activation: Challenges and Possibilities for Improvement	extraction, proton, radioactivity, target	611
	M.A. Fraser, B. Balhan, H. Bartosik, C. Bertone, D. Björkman, J.C.C.M. Borburgh, N. Conan, K. Cornelis, R. Garcia Alia, L. Gatignon, B. Goddard, Y. Kadi, V. Kain, A. Mereghetti, F. Roncarolo, P.M. Schicho, J. Spanggaard, O. Stein, L.S. Stoel, F.M. Velotti, H. Vincke CERN, Geneva, Switzerland
	In 2015 the highest integrated number of protons in the history of the North Area was slow extracted from the CERN Super Proton Synchrotron (SPS) for the Fixed Target physics programme. At well over 1.10¹⁹ protons on target (POT), this represented the highest annual figure at SPS for almost two decades, since the West Area Neutrino Facility was operational some 20 years ago. The high intensity POT requests have continued into 2016-17 and look set to do so for the foreseeable future, especially in view of the proposed SPS Beam Dump Facility and experiments, e.g. SHiP, which are requesting up to 4·10¹⁹ POT per year. Without significant improvements, the attainable annual POT will be limited to well below the total the SPS machine could deliver, due to activation of accelerator equipment and associated personnel dose limitations. In this contribution, the issues arising from the recent high activation levels are discussed along with the steps taken to understand, manage and mitigate these issues. The research avenues being actively pursued to improve the slow extraction related beam loss for present operation and future requests are outlined, and their relative merits discussed. A. Golutvin et al., ‘‘A Facility to Search for Hidden Particles (SHiP) at the CERN SPS'', CERN, Geneva, Switzerland, Rep. CERN-SPSC-2015-016 (SPSC-P-350), Apr. 2015.
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MOPIK046	Phase Space Folding Studies for Beam Loss Reduction During Resonant Slow Extraction at the CERN SPS	extraction, multipole, sextupole, proton	615
	L.S. Stoel, M. Benedikt, K. Cornelis, M.A. Fraser, B. Goddard, V. Kain, F.M. Velotti CERN, Geneva, Switzerland
	The requested number of protons slow-extracted from the CERN Super Proton Synchrotron (SPS) for Fixed Target (FT) physics is expected to continue increasing in the coming years, especially if the proposed SPS Beam Dump Facility is realised. Limits on the extracted intensity are already being considered to mitigate the dose to personnel during interventions required to maintain the extraction equipment, especially the electrostatic extraction septum. In addition to other on-going studies and technical developments, a reduction of the beam loss per extracted proton will play a crucial role in the future performance reach of the FT experimental programme at the SPS. In this paper a concept is investigated to reduce the fraction of beam impacting the extraction septum by folding the arm of the phase space separatrix. Beam dynamics simulations for the concept are presented and compared to the phase space acceptance of the extraction channel. The performance potential of the concept at SPS is evaluated and discussed alongside the necessary changes to the non-linear optical elements in the machine.
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MOPIK050	Reduction of Resonant Slow Extraction Losses with Shadowing of Septum Wires by a Bent Crystal	extraction, proton, collimation, septum	631
	F.M. Velotti, M.A. Fraser, B. Goddard, V. Kain, W. Scandale, L.S. Stoel CERN, Geneva, Switzerland
	A new experiment, SHiP, is being studied at CERN to investigate the existence of three Heavy Neutral Leptons in order to give experimental proof to the proposed neutrino minimal Standard Model. High-intensity slow-extraction of protons from the SPS is a pre-requisite for SHiP. The experiment requires a resonant extraction with in a 7.2 s cycle, and about 4·10¹³ protons extracted at 400 GeV in a 1 s flat-top, to achieve the needed 2·10²⁰ protons on target in five years. Although the SPS has delivered this in the past to the CNGS experiment with fast extraction, for SHiP beam losses and activation of the SPS electrostatic extraction septum (ZS) could be a serious performance limitation, since the target number of protons to resonantly extract per year is a factor of two higher than ever achieved before and a factor of four than ever reached with the third-integer slow extraction. In this paper, a novel extraction technique to significantly reduce the losses at the ZS is proposed, based on the use of a bent crystal to shadow the septum wires. Theoretical concepts are developed, the performance gain quantified and a possible layout proposed.
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MOPIK055	Beam by Design: Current Pulse Shaping Through Longitudinal Dispersion Control	electron, sextupole, synchrotron, laser	644
	T.K. Charles, D.M. Paganin Monash University, Faculty of Science, Clayton, Victoria, Australia M.J. Boland The University of Melbourne, Melbourne, Victoria, Australia M.J. Boland, R.T. Dowd SLSA, Clayton, Australia
	Electron beams traversing a dispersive region, such as a bunch compressor and some transport line can form caustic lines and surfaces corresponding to regions of maximum electron density, which influence the current pulse shape. In this paper, we present a technique to manipulate the longitudinal phase space distribution to achieve an arbitrary, desired current pulse shape. We show how sextupole magnets (and in certain circumstances, octupole magnets), placed within a dispersive region can be used to generate the conditions required for a flexible technique of current pulse shaping that avoids truncation through collimation.
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MOPIK057	Strategy of Beam Tuning Implementation for the SARAF MEBT and SC Linac	linac, solenoid, quadrupole, focusing	652
	P.A.P. Nghiem, D. Uriot CEA/DSM/IRFU, France B. Dalena, J. Dumas, N. Pichoff CEA/IRFU, Gif-sur-Yvette, France
	Beam dynamics of the MEBT and Superconducting Linac in the SARAF accelerator are being finalized. A strategy for beam tuning implementation is applied to this section, leading to specifying the complete set of error tolerances / beam measurements / correctors. A systematic and precise methodology in several steps is applied, leading to fairly distributing the error budget, from which correction schemes are studied, allowing to determine the necessary beam measurements and correctors.
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MOPIK058	Beam Dynamic Studies for the SARAF MEBT and SC Linac	quadrupole, linac, cavity, rfq	655
	J. Dumas, N. Pichoff, D. Uriot CEA/IRFU, Gif-sur-Yvette, France P.A.P. Nghiem CEA/DSM/IRFU, France
	The SARAF MEBT and Super Conducting Linac (SCL) transport and accelerate deuterons or protons from the RFQ to the final energy. In this report, beam dynamics studies for this section are described. A rational distribution of the different roles of the MEBT leads to defining its necessary quadrupole/rebuncher composition. This allows easy beam re-tuning following changes from the RFQ or the SC Linac. After observing evidences of beam losses mainly due to phase unhooking, efforts have been dedicated to enlarge the SCL longitudinal acceptance. A combination of cavity field phases is found so that the required final beam energy is also fulfilled.
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MOPIK075	Design, Simulation and Compare of Flat Cathode Electron Guns with Spherical Cathode Electron Guns for Industrial Accelerators	cathode, gun, electron, space-charge	702
	M. Nazari, F. Abbasi Shahid Beheshti University, Tehran, Iran S. Ahmadiannamin ILSF, Tehran, Iran F. Ghasemi NSTRI, Tehran, Iran S. Haghtalab IPM, Tehran, Iran
	In this article, electron guns with flat and spherical cathodes have been designed and simulated for industrial accelerators. After checking the different features of each cathode geometry, there has been discussed about optimum values of this features. The most important features in selecting the best cathode geometry for industrial accelerators are beam waist radius, beam waist position, current density and price. Finally after comparing the different features of both geometries with each other, suitable geometry was selected.
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MOPIK076	Optimization of Dynamic Aperture with Constraints on Linear Chromaticity	luminosity, sextupole, coupling, lattice	705
	H. Sugimoto, H. Koiso, A. Morita, Y. Ohnishi, K. Oide, D. Zhou KEK, Ibaraki, Japan
	This paper presents numerical technique to optimize dynamic aperture with constraints on linear chromaticity of optical functions. By solving a set of linear equations at each iteration step of dynamic aperture optimization, the linear chromaticity is kept unchanged. The variable range of tuning knobs is taken into account in order to make the technique applicable to practical use. Numerical simulations assuming the SuperKEKB design lattice are performed, and it is demonstrated that the dynamic aperture obtained with the presented scheme is almost comparable to that without constraints. Luminosity simulations assuming weak-strong model show that the constraints lead to improvements of luminosity performance.
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MOPIK078	Narrow-Band, Wide-Range Tuneable THz Source Based on the Slotted-Foil Technique	undulator, electron, radiation, FEL	712
	J. Pfingstner, E. Adli, H. Holmestad University of Oslo, Oslo, Norway S. Bettoni, S. Reiche PSI, Villigen PSI, Switzerland
	The FEL user community has expressed a strong interest in a THz source for the excitation of their samples in pump probe experiments. The demanded THz properties are challenging to achieve, as they include a narrow bandwidth of <5-10%, the possibility of frequency tuning between 1 and 20 THz, a THz pulse energy of about 100 uJ, and a fixed phase relation from shot-to-shot. To fulfil these specifications, an accelerator-based source is proposed in this paper. It utilises the slotted-foil technique to create a pre-bunched electron beam that is injected into a helical undulator. Detailed simulation studies presented in this paper show that the corresponding undulator radiation has the demanded properties.
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MOPIK081	Study of HEPS Performance with Error Model and Simulated Correction	optics, quadrupole, sextupole, closed-orbit	721
	D. Ji, Z. Duan, S.K. Tian, Y. Wei IHEP, Beijing, People's Republic of China
	As an important component of physics study on High Energy Photon Source (HEPS), error modelling and simu-lated correction will provide the guideline to restrict the manufacture redundancy of the hardware and estimate the real machine performance. In this paper, we present some work on error effect evaluation and simulated commis-sioning based on a recent lattice design.
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MOPIK087	Development of a Tune Knob for the HLS-II Storage Ring	quadrupole, storage-ring, lattice, sextupole	730
	S.W. Wang, J.Y. Li, W.B. Wu, W. Xu, K. Xuan, X. Zhou USTC/NSRL, Hefei, Anhui, People's Republic of China
	A tune knob is a useful tool for lattice setup and machine studies in a storage ring. It is used to adjust the transverse tunes with a small impact on the beam dynamics. A global tune knob is designed for the Hefei Light Source (HLS). In the tune knob, the quadrupoles are grouped into four families and are symmetrically adjusted. Methodical Accelerator Design-X (MAD-X) is used to calculate the coefficients of the tune knob and the Accelerator Toolbox (AT) is used to double check the accuracy of the tune knob. The chromaticity is corrected by the sextupoles in the storage ring. This paper reports preliminary simulation results of the tune knob for HLS. The beta function deviations are also studied.
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MOPIK092	Computer Modelling of the SC202 Superconducting Cyclotron for Hadron Therapy	cyclotron, extraction, resonance, proton	742
	O. Karamyshev, V. Malinin, D.V. Popov JINR/DLNP, Dubna, Moscow region, Russia Y.F. Bi, G. Chen, K.Z. Ding, Y. Song ASIPP, Hefei, People's Republic of China G.A. Karamysheva, N.A. Morozov, E.V. Samsonov, G. Shirkov, S.G. Shirkov JINR, Dubna, Moscow Region, Russia
	The SC202 superconducting cyclotron for hadron therapy is under development by collaboration of ASIPP (Hefei, China) and JINR (Dubna, Russia). The accelerator will provide about 200 MeV proton beam with maximum current of 1μA in 2017-2018. We have performed simulations of all systems of the SC202 cyclotron and specified the main parameters of magnet, acceleration system and extraction elements.
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MOPIK096	Predictability of the Beam Quality During RFQ Voltage Tuning	emittance, rfq, distributed, quadrupole	748
	A. Ponton ESS, Lund, Sweden A.C. France CEA/IRFU, Gif-sur-Yvette, France
	It has previously been demonstrated that certain spatial harmonics of the dipolar and quadrupolar components of the RFQ voltage have stronger effects on the beam quality than others. The study suggested that, during the tuning process to compensate for manufacturing errors, some harmonic contents (other than the first ones) should be minimized. The analysis presented in this paper looks at how we can predict the beam quality knowing the content of each voltage harmonics. We propose also a strategy to minimize the impacts of the voltage errors on the output beam phase space during the tuning phase. A. Ponton, A.C. France, Y.I. Levinsen, O. Piquet, B. Pottin, and E. Sargsyan, Voltage Error Studies in the ESS RFQ, in Proc. 7th International Particle Accelerator Conference (IPAC'16), Busan, Korea, May 2016, paper THPMB039, pp. 3320-3323, ISBN: 978-3-95450-147-2
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MOPIK104	Top-Up Injection With Anti-Septum	septum, injection, kicker, storage-ring	774
	C.H. Gough, M. Aiba PSI, Villigen PSI, Switzerland
	We present a novel improvement for injection into the very restricted machine aperture of future light source synchrotrons. A conventional injection scheme is based on a septum to deflect the injected bunch plus a fast pulsed three or four kicker bump to bring the stored beam close to the septum wall. With the novel improvement, the bump kickers are fitted with a thin wall longitudinal metal plate which screens the injected bunch from deflection without changing the stored beam bump behaviour. This metal screen then forms the final septum, but inverted in function of the conventional approach, hence the name anti-septum. The approach does not remove the need for the main septum magnet, but for modest cost it permits the injected bunch to be brought closer to the stored beam. Application of the anti-septum to the SLS-2 project and simulation results on a prototype are presented.
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MOPIK107	Injection Efficiency Simulation in the Electron Storage Ring of X-Ray Generator NESTOR	storage-ring, injection, electron, alignment	784
	A.Y. Zelinsky, P. Gladkikh, A.A. Kalamayko NSC/KIPT, Kharkov, Ukraine
	In the paper the results of the beam dynamics and injection efficiency simulation in the storage ring of the X-ray generator NESTOR are presented.
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MOPIK108	Tuning Simulations for the CLIC Traditional Beam Delivery System	luminosity, lattice, collider, linear-collider	788
	R.M. Bodenstein, P. Burrows JAI, Oxford, United Kingdom E. Marín, F. Plassard, R. Tomás CERN, Geneva, Switzerland
	As the design of the CLIC Beam Delivery System (BDS) evolves, tuning simulations must be performed on each of the proposed lattice designs to see which system achieves the highest luminosity in the most realistic manner. This work will focus on the tuning simulations performed on the so-called Traditional lattice design for the center-of-mass energy of 3 TeV. The lattice modifications required to target the most important aberrations and the latest tuning results will be presented.
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MOPIK113	Beam Phase Space Tomography for FXR LIA	emittance, space-charge, solenoid, electron	801
	Y.H. Wu, Y.-J. Chen LLNL, Livermore, California, USA
	Funding: This work was performed under the auspices of the U.S. Department of Energy by Lawrence Livermore National Laboratory under Contract DE-AC52-07NA27344. Knowing the initial beam parameters entering an accelerator or a downstream beamline allows us to select transport tunes optimized for a desired accelerator performance. In this study, we report unfolding LLNL's FXR [1] beam parameters by using the tomography technique [2, 3] to construct the beam phase space along the accelerator's downstream beamline. The unfolded phase spaces from tomography and simulations are consistent.
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MOPIK114	End-to-End Energy Variation Study for Induction Radiography Accelerator	target, emittance, beam-transport, solenoid	804
	Y.H. Wu, Y.-J. Chen LLNL, Livermore, California, USA
	Funding: This work was performed under the auspices of the U.S. Department of Energy by Lawrence Livermore National Laboratory under Contract DE-AC52-07NA27344. Energy variation study for beam transport from the entrance of a conceptual induction radiography accelerator to the x-ray target has been reported previously [1]. In this report, we have extended the study upstream to the injector. To achieve minimum emittance growth and to obtain a desired final beam size, we have developed three optimal tunes. Among them, one optimal tune, capable of supressing beam break-up instability and producing acceptable corkscrew motions, is used to study the energy variation effects on radiography performance. The study shows that ±3% energy variation is acceptable.
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MOPIK115	A Design for 10 GeV, High Peak-Current, Tightly Focused Electron Beams at FACET-II	emittance, linac, electron, acceleration	807
	G.R. White SLAC, Menlo Park, California, USA
	Funding: This work was sponsored by the Department of Energy under Contract Number: DE-AC02-76SF00515 FACET-II will be a new test facility, starting construction in 2018 within the main SLAC Linac. Its purpose is to build on the decades-long experience developed conducting accelerator R&D at SLAC in the areas of advanced acceleration and coherent radiation techniques with high-energy electron and positron beams. The design consists of a 135-MeV high-brightness photo-injector constructed in an off-axis injection line in Sector 10 of the SLAC Linac, two new 4-bend chicane bunch compressors installed in Sectors 11 and 14, with a third compression stage provided by the existing FACET W Chicane in Sector 20. We develop a design to deliver peak currents more than 160 kA to the Sector 20 interaction region at 10 GeV, with 10 'm-rad emittances at 2 nC bunch charge and 1.4 % rms energy spread. The Sector 20 bunch compressor is re-designed for maximum peak current throughput and minimal emittance degradation via CSR, and the FACET-II compression scheme is optimized. We present 6D start-end beam tracking simulations using Lucretia including ISR, CSR, wakefields and space charge effects.
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MOPIK117	On the Computation of Phase and Energy Gain for a Thin-Lens RF Gap Using a General Field Profile	linac, factory, acceleration, cavity	810
	C.K. Allen ORNL, Oak Ridge, Tennessee, USA
	Funding: This material is based upon work supported by the U.S. Department of Energy, Office of Science, Office of Basic Energy Sciences under contract number DE-AC05-00OR22725. The thin-lens representation for an RF accelerating gap has been well developed and is documented by Lapostolle [5], Weiss [6], Wangler [14], and others [9], [10]. These models assume that the axial electric field is both centered and symmetric so it has a cosine expansion. Presented here is a model that considers general axial fields. Both the cosine and sine transit time factors are required plus their Hilbert transforms. The combination yields a complex Hamiltonian rotating in the complex plane with the synchronous phase. The phase and energy gains are computed in the pre-gap and post-gap regions then aligned with asymptotic values of wave number. Derivations are outlined, examples are shown, and simulations presented.
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MOPIK118	Model Based Optics Studies in the MEBT Section of SNS	emittance, linac, lattice, rfq	814
	A.P. Shishlo, A.V. Aleksandrov, A.P. Zhukov ORNL, Oak Ridge, Tennessee, USA Y. Liu KEK/JAEA, Ibaraki-Ken, Japan
	Funding: This manuscript has been authored by UT-Battelle, LLC, under Contract No. DE-AC0500OR22725 with the U.S. Department of Energy. The paper presents the beam dynamics studies for the Medium Energy Beam Transport (MEBT) section of the Spallation Neutron Source (SNS) accelerator. The analysis of measurements is based on the PyORBIT linac model. The diagnostics data includes wire scanners' profiles, slit-harp and slit-slit transverse emittances, MEBT re-bunchers calibration data, and bunch length measurements. The MEBT is a matching section between RFQ and a Drift Tube Linac (DTL). It is also a place for beam halo scraping which helps to reduce beam loss in downstream linac sections. The linac simulation code was benchmarked against the diagnostics data.
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MOPIK123	Beam Dynamics Numerical Studies Regarding CBETA Cornell-BNL ERL	lattice, quadrupole, multipole, optics	824
	F. Méot, S.J. Brooks, D. Trbojevic, N. Tsoupas BNL, Upton, Long Island, New York, USA S.C. Tygier UMAN, Manchester, United Kingdom
	Funding: Work supported by New York State Energy Research and Development Authority (NYSERDA) The Cornell-BNL Electron Test Accelerator CBETA is based on a 36 MeV superconducting linac and on a single 4-pass up/4-pass down linear FFAG return loop, for beam acceleration from 6 to 150 MeV and energy recovery. Numerical beam dynamics simulations have accompanied and eventually validated the quadrupole-doublet FFAG cell technology and parameters, and following that the complete return loop, all along the ERL lattice design process. They are key to assessing and validating the ERL optics and beam behavior over the whole acceleration/ER cycle, and in preparing future machine operation. This paper presents various of these beam dynamics studies, including start-to-end simulations.
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MOPVA007	Simulations for Beam-Based Measurements in BERLinPro	cavity, diagnostics, gun, optics	859
	M. McAteer, M. Abo-Bakr, J. Knedel, G. Kourkafas, B.C. Kuske, J. Völker HZB, Berlin, Germany
	BERLinPro is an energy recovery linac project whose goal is to establish the accelerator physics knowledge and technology needed to produce 50 MeV beams with high current, low normalized emittance, and low losses. Precise measurements of beam parameters are essential for demonstrating the achievement of performance goals. In this paper we present simulations for measurements of energy, energy spread, and bunch length using the tracking code Astra.
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MOPVA020	S2E Simulation of an ERL-Based High-Power EUV-FEL Source for Lithography	FEL, linac, electron, injection	894
	N. Nakamura, R. Kato, T. Miyajima, M. Shimada KEK, Ibaraki, Japan R. Hajima QST, Tokai, Japan T. Hotei Sokendai, Ibaraki, Japan
	An energy recovery linac(ERL)-based free electron laser(FEL) is a possible candidate of a high-power EUV source for lithography. The ERL can provide a high-current and high-quality electron beam for the high-power FEL and also greatly reduce the dumped beam power and activation compared to ordinary linacs. An ERL-based EUV-FEL source has been designed using available technologies and resources. For this design, we perform Start-to-End(S2E) simulation from the electron gun to the exit of the decelerating main linac to track the electron beam parameters and to evaluate the FEL performance. The electron bunches from the injector are off-crest accelerated to 800 MeV and compressed in the 1st arc and/or chicane to obtain a high-peak current for high FEL output. After the undulator section for SASE FEL, they are decompressed in the 2nd arc and then decelerated in the main linac to optimize the energy spread or the energy recovery efficiency. This paper will present the S2E simulation for the designed EUV-FEL source. N. Nakamura et al., Proc. of ERL2015, Stony Brook, NY, USA, pp.4-9.
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MOPVA025	Step-Like Field Magnets to Uniform Beam Distribution and Experiment at CADS Injector-I	target, dipole, experiment, proton	908
	C. Meng, Y. Chen, H. Geng, J.Y. Tang, F. Yan, L. Yu, Y.L. Zhao IHEP, Beijing, People's Republic of China
	High power is the development tendency of proton accelerator, so obtaining uniform beam distribution on target becomes more and more important and critical. The method of using step-like field magnets to obtain a uniform beam distribution on target was presented. In the beamdump line of CADS injector-I test facility four step-like field magnets have been installed to uniform beam distribution to reduce the maximum current density on the beamdump. The magnetic field of step-like field magnets have been measured and discussed in this paper. The simulation results and measurement results of beam uniformization are presented.
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MOPVA039	Manufacturing and Validation Tests of IFMIF Low-Beta HWRs	cavity, cryomodule, SRF, operation	942
	G. Devanz, F. Éozénou, L. Maurice, P. Sahuquet, C. Servouin CEA/DSM/IRFU, France N. Bazin, P. Carbonnier, P. Charon, G. Disset, P. Hardy, E. Jacques, O. Piquet, D. Roudier CEA/IRFU, Gif-sur-Yvette, France J.K. Chambrillon, T. Percerou CEA/DRF/IRFU, Gif-sur-Yvette, France
	The IFMIF accelerator aims to provide an accelerator-based D-Li neutron source to produce high intensity high energy neutron flux to test samples as possible candidate materials to a full lifetime of fusion energy reactors. A prototype of the low energy part of the accelerator is under construction at Rokkasho in Japan. It includes one cryomodule containing 8 half-wave resonators (HWR) operating at 175 MHz .The first manufactured HWR has passed low power tests at 4.2K in vertical cryostat succesfully and exceeds the specifications. It has also been tested in the dedicated horizontal Sathori cryostat equiped with its cold tuning system. The serial production and qualification tests of the 8 cavities which will eventually equip the cryomodule are carried out in parallel. In this paper, we focus on the HWR preparation and test results and give a status of the manufacturing activities.
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MOPVA042	CEA Preliminary Design of the Cryomodules for SARAF Phase II Superconducting Linac	cavity, cryomodule, vacuum, alignment	951
	R. Cubizolles, P. Brédy, D. Chirpaz-Cerbat, P. Hardy, F. Leseigneur, C. Madec, J. Plouin CEA/IRFU, Gif-sur-Yvette, France N. Bazin CEA/DSM/IRFU, France R. Bruce, Th. Plaisant CEA/DRF/IRFU, Gif-sur-Yvette, France
	CEA is committed to deliver a Medium Energy Beam Transfer line and a superconducting linac (SCL) for SARAF accelerator in order to accelerate 5mA beam of either protons from 1.3 MeV to 35 MeV or deuterons from 2.6 MeV to 40.1 MeV. The SCL consists of 4 cryomodules and 4 warm sections with diagnostics at the end of each cryomodule. The first two identical cryomodules host 6 half-wave resonator (HWR) low-beta cavities (β = 0.091), 176 MHz, and 6 focusing superconducting solenoids. The last two identical cryomodule welcome 7 HWR high-beta cavities (β = 0.181), 176 MHz, and 4 solenoids. The paper will presents the preliminary design of the cryomodules.
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MOPVA048	Simulation of the Thermoelectrically Generated Magnetic Field in a SC Nine-Cell Cavity	cavity, SRF, operation, superconducting-RF	968
	J.M. Köszegi, J. Knobloch, O. Kugeler HZB, Berlin, Germany
	Several studies showed that thermocurrents generate a magnetic field in a horizontal cavity test assembly or cryomodul, which may get trapped during the supercon-ducting phase transition. The trapped flux causes additional dissipation in the order of 1 to 10 n' during operation and can therefore significantly degrade the quality factor in a TESLA cavity. We simulated the distribution of the generated magnetic field over the whole cavity-tank system for an asymmetric temperature distribution. The asymmetry allows the field to penetrate the RF surface which would be field free in the symmetric case. The calculated results complemented a direct measurement of trapped magnetic flux inside the cavity with a small number of field probes. Finally, the obtained data was combined with RF measurements in three passband modes to determine the overall distribution of trapped magnetic flux due to thermocurrents.
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MOPVA051	Design of the High Power 1.5 GHz Input Couplers for BESSY VSR	coupling, cavity, operation, HOM	978
	E. Sharples, M. Dirsat, J. Knobloch, A.V. Vélez HZB, Berlin, Germany
	The Variable pulse length Storage Ring (BESSY VSR) upgrade to BESSY II at Helmholtz-Zentrum Berlin (HZB) requires an upgrade on the RF systems in the form of high-voltage longitudinally focusing super conducting RF cavities of 1.5 GHz ad 1.75 GHz. For operation, coaxial RF power couplers capable of handling 13 kW peak power at standing wave operation are required for both the 1.5 GHz and 1.75 GHz cavities. The coupler is based on a design by Cornell University with modifications to suit frequency and coupling requirements. The coupler is intended to provide variable coupling with a range of Qext from 6x10⁶ to 6x10⁷ to allow flexibility to adjust to operating conditions of BESSY VSR. Here we present the RF design of the high-power coaxial coupler for BESSY VSR along with the design of the test stand for conditioning a pair of couplers.
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MOPVA054	High Power RF Coupler for the CW-Linac Demonstrator at GSI	cavity, Windows, linac, ion	990
	M. Heilmann, W.A. Barth, S. Yaramyshev GSI, Darmstadt, Germany M. Amberg, M. Basten, R. Blank, M. Busch, F.D. Dziuba, H. Podlech, M. Schwarz IAP, Frankfurt am Main, Germany K. Aulenbacher IKP, Mainz, Germany K. Aulenbacher, W.A. Barth, V. Gettmann, M. Miski-Oglu HIM, Mainz, Germany W.A. Barth, S. Yaramyshev MEPhI, Moscow, Russia
	The planned super-heavy element (SHE) research project investigates heavy ions near the coulomb barrier in future experiments. A superconducting (sc) continuous wave (cw) CH-Linac Demonstrator was developed and installed behind the High Charge State Injector (HLI) at GSI Darmstadt, Germany. In future the advanced cw-LINAC setup, with several CH-cavities, will accelerates the heavy ion beam from HLI with an energy of 1.4 MeV/u up to 3.5 - 7.3 MeV/u. The RF power of several kW will be coupled capacitively into the CH-cavities with minimal reflection at an operation frequency of 217 MHz. Two ceramic windows (Al2O3) are installed inside the RF coupler, to reduce the premature contamination of the cavity and as an additional vacuum barrier. The CH-cavity will be operated at cryogenic temperature (4 K) and will be increased to room temperature along the RF coupler. The optimally adapted RF coupler design, providing minimal RF losses and simultaneously maximal performance, was optimized by electromagnetic simulations. An RF coupler design with a reflection-free RF adaptor as well as the temperature distribution along the coupler will be presented.
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MOPVA064	Multipacting Study in INFN-LASA ESS Medium-Beta Cavity	cavity, SRF, site, electron	1019
	J.F. Chen, M. Bertucci, A. Bosotti, P. Michelato, L. Monaco, C. Pagani, R. Paparella, D. Sertore INFN/LASA, Segrate (MI), Italy S. Pirani ESS, Lund, Sweden
	We present Multipacting studies in ESS Medium-Beta cavities of INFN-LASA design with both simulation and experimental results. The simulation on the ideal cavity shape with both FishPact and MultiPac2.1 codes shows that multipacting appears in a very small region near equator where the weld seam exists. A simulation with more realistic cavity shape considering the weld seam at cell equators has also been done out showing similar results for end cell but a remarkable mitigation for inner cell. During the vertical tests at LASA, Multipacting is frequently observed but with no limitation to the cavity performance, which well confirms the MP predicted by the simulations.
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MOPVA087	Low Betta Superconducting Cavity for the New Injector Linac for Nuclotron-NICA	cavity, linac, multipactoring, accelerating-gradient	1058
	M. Gusarova, T.A. Bakhareva, M.V. Lalayan, S.V. Matsievskiy, N.P. Sobenin, D.V. Surkov, K.V. Taletskiy, V. Zvyagintsev MEPhI, Moscow, Russia A.A. Bakinowskaya, V.S. Petrakovsky, A.I. Pokrovsky, D.A. Shparla Physical-Technical Institute of the National Academy of Sciences of Belarus, Minsk, Belarus A.V. Butenko, G.V. Trubnikov JINR/VBLHEP, Dubna, Moscow region, Russia V. Zvyagintsev TRIUMF, Vancouver, Canada
	The results of the RF, mechanical and multipactor discharge simulations of the 162 MHz quarter wave resonator (QWR) for New Superconducting Injector Linac for Nuclotron-NICA are presented. Cavity design in conjunction with manufacturing features is discussed.
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MOPVA088	Medium Betta Superconducting Cavity for the New Injector Linac for Nuclotron-NICA	cavity, linac, multipactoring, accelerating-gradient	1061
	M. Gusarova, M.V. Lalayan, N.P. Sobenin, D.V. Surkov, K.V. Taletskiy MEPhI, Moscow, Russia A.A. Bakinowskaya, V.S. Petrakovsky, A.I. Pokrovsky, D.A. Shparla Physical-Technical Institute of the National Academy of Sciences of Belarus, Minsk, Belarus A.V. Butenko, G.V. Trubnikov JINR/VBLHEP, Dubna, Moscow region, Russia
	The results of the electrodynamical and multipactor discharge simulations of the medium betta superconducting cavity for New Superconducting Injector Linac for Nuclotron-NICA are presented. Different designs of CH and Spoke cavities are compared and the optimal one is chosen.
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MOPVA091	Investigation of HOM Frequency Shifts Induced by Mechanical Tolerances	cavity, HOM, operation, cryogenics	1071
	S. Pirani, M. Eshraqi, M. Lindroos ESS, Lund, Sweden A. Bosotti, J.F. Chen, P. Michelato, C. Pagani, R. Paparella, D. Sertore INFN/LASA, Segrate (MI), Italy T.P.Å. Åkesson Lund University, Department of Physics, Lund, Sweden
	We present Higher Order Mode (HOM) studies on ESS Medium-Beta cavity of INFN-LASA design, including both simulation and measurement results. Mechanical tolerances of the fabrication process might shift HOMs frequencies toward harmonics of the bunch frequency. Both simulation and measurements at room and cryogenic temperature show that INFN LASA cavity is fully compatible with ESS requirements.
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MOPVA097	Finite Element Analysis on Helium Discharge from Superconducting RF in the Storage Ring Tunnel	cryogenics, SRF, cavity, distributed	1085
	J.-C. Chang, F. Z. Hsiao, J.C. Huang, S.P. Kao, H.C. Li, W.R. Liao, C.Y. Liu, H.H. Tsai, Z.-D. Tsai NSRRC, Hsinchu, Taiwan
	Liquid helium for transferring cooling power from the cryogenic plant to the magnets and SRF cavities had been widely applied on the advanced large superconducting particle accelerators. For requirements of high stable and reliable operation, many efforts have been put into the improvement and modification of the cryogenic system. However, personnel safety is another critical issue of the cryogenic system. Once large liquid helium was released on the atmospheric tunnel, the volume of helium will expand several hundred times and cause oxygen deficiency in short time due to sudden change of helium density. In this study, we applied numerical simulation to analyze helium discharge through a SRF cavity in the TPS tunnel.
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MOPVA100	Atomic Layer Deposition of Niobium Nitride from Different Precursors	plasma, niobium, experiment, controls	1094
	P. Pizzol, P. Chalker, J.W. Roberts, J. Wrench The University of Liverpool, Liverpool, United Kingdom O.B. Malyshev, R. Valizadeh STFC/DL/ASTeC, Daresbury, Warrington, Cheshire, United Kingdom
	Advancements in technology have taken bulk niobium cavities close to their theoretical operational limits of 45 MV/m, pushing the research to explore novel materials, such as niobium based alloys . Theoretical studies suggest that a composite material composed of alternative superconductor / insulator multilayers would surpass the bulk niobium limits. Chemical vapour deposition (CVD) can deposit mi-crons thick Nb films in less than an hour, at the expense of precise thickness control. Atomic layer deposition (ALD), instead, even if considerably slower than CVD can be used in applications where the thickness of the deposited layers needs to be controlled with a resolution down to the nanometer. This article presents the preliminary results obtained by using plasma assisted ALD techniques to deposit NbN based compounds starting from chlorinated precursors and organic ones, and the design for a new deposition system currently being built at the Daresbury Laboratories.
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Paper

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MOZA1

Electron Cloud Effects at the LHC and LHC Injectors

electron, operation, emittance, dipole

30

G. Rumolo, H. Bartosik, E. Belli, P. Dijkstal, G. Iadarola, K.S.B. Li, L. Mether, A. Romano, M. Schenk, F. Zimmermann
CERN, Geneva, Switzerland
E. Belli
University of Rome La Sapienza, Rome, Italy
P. Dijkstal
TU Darmstadt, Darmstadt, Germany
M. Schenk
EPFL, Lausanne, Switzerland

Electron cloud effects are one of the main limitations of the performance of the LHC and its injectors. Enormous progress has been done in the simulation of the electron cloud build-up and of the effects on beam stability while mitigation measures have been identified and implemented (scrubbing, low secondary electron yield coatings, etc.). The above has allowed reaching nominal beam parameters in the LHC during Run 2. A review of the studies and results obtained and the strategy and expected performance for the High Luminosity operation of the LHC will be presented.

Slides MOZA1 [12.855 MB]

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MOOCA1

High Efficiency Klystrons Using the COM Bunching Technique

klystron, electron, cavity, bunching

37

D.A. Constable
Lancaster University, Lancaster, United Kingdom
A.Yu. Baikov
Moscow University of Finance & Law, Moscow, Russia
G. Burt
Cockcroft Institute, Lancaster University, Lancaster, United Kingdom
R.D. Kowalczyk
L-3, Williamsport, Pennsylvania, USA
I. Syratchev
CERN, Geneva, Switzerland

Future large-scale particle accelerators, for example, the Future Circular Collider (FCC), the Compact Linear Collider (CLIC) and the International Linear Collider (ILC), will require significant RF drive power on the order of 100 MW. Thus, an RF source with high efficiency is preferable to minimise the overall power required. Klystrons represent an attractive RF source, with the current state of the art operating at efficiencies of up to 70%. Such devices feature monotonic bunching, where at the output cavity, a number of electrons will not be in the main bunch, and instead will be present in the anti-bunch, and therefore not contributing to the output power. Therefore, novel bunching methods, such as the Core Oscillation Method (COM), are worthy of investigation. By allowing the core of the electron beam to bunch and de-bunch between successive cavities, the number of electrons contained in the final bunch can increase, and therefore improve the efficiency of the device. Numerical simulation of klystrons featuring COM will be presented, with efficiencies of up to 85% being predicted thus far.

Slides MOOCA1 [12.765 MB]

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MOPAB001

Status of the FCC-hh Collimation System

collimation, insertion, proton, collider

64

J. Molson, A. Faus-Golfe
LAL, Orsay, France
R. Bruce, M. Fiascaris, A.M. Krainer, S. Redaelli
CERN, Geneva, Switzerland

Funding: Funding from the European Union's Horizon 2020 research and innovation programme under grant No 654305.
The future circular hadron collider (FCC-hh) will have an unprecedented proton beam energy of 50 TeV, and total stored beam energy of 8.4 GJ. We discuss current developments in the collimation system design, and methods with which the challenges faced due to the high energies involved can be mitigated. Finally simulation results of new collimation system designs are presented.

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MOPAB003

Energy Deposition in the Betatron Collimation Insertion of the 100 TeV Future Circular Collider

dipole, insertion, proton, betatron

68

M.I. Besana, C. Bahamonde Castro, A. Bertarelli, R. Bruce, F. Carra, F. Cerutti, A. Ferrari, M. Fiascaris, A. Lechner, A. Mereghetti, S. Redaelli, E. Skordis, V. Vlachoudis
CERN, Geneva, Switzerland

The FCC proton beam is designed to carry a total energy of about 8500 MJ, a factor of 20 above the LHC. In this context, the collimation system has to deal with extremely tight requirements to prevent quenches and material damage. A first layout of the betatron cleaning insertion was conceived, adapting the present LHC collimation system to the FCC lattice. A crucial ingredient to assess its performance, in particular to estimate the robustness of the protection devices and the load on the downstream elements, is represented by the simulation of the particle shower generated at the collimators, allowing detailed energy deposition estimations. This paper presents the first results of the simulation chain starting from the proton losses generated with the Sixtrack-FLUKA coupling, as currently done for the present LHC and for its upgrade. Expectations in terms of total power, peak power density and integrated dose on the different accelerator components are presented.

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MOPAB012

Study of the 2015 Top Energy LHC Collimation Quench Tests Through an Advanced Simulation Chain

ion, proton, collimation, heavy-ion

100

E. Skordis, C.P. Welsch
The University of Liverpool, Liverpool, United Kingdom
R. Bruce, F. Cerutti, A. Ferrari, P.D. Hermes, A. Lechner, A. Mereghetti, S. Redaelli, B. Salvachua, E. Skordis, V. Vlachoudis
CERN, Geneva, Switzerland
C.P. Welsch
Cockcroft Institute, Warrington, Cheshire, United Kingdom

While the LHC has shown record-breaking perfor-mance during the 2016 run, our understanding of the behaviour of the machine must also reach new levels. The collimation system and especially the betatron cleaning insertion region (IR7), where most of the beam halo is intercepted to protect superconducting (SC) magnets from quenching, has so far met the expectations but could nonetheless pose a bottleneck for future operation at higher beam intensities for HL-LHC. A better under-standing of the collimation leakage to SC magnets is required in order to quantify potential limitations in terms of cleaning efficiency, ultimately optimising the collider capabilities. Particle tracking simulations com-bined with shower simulations represent a powerful tool for quantifying the power deposition in magnets next to the cleaning insertion. In this study, we benchmark the simulation models against beam loss monitor measure-ments from magnet quench tests (QT) with 6.5 TeV pro-ton and 6.37Z TeV Pb ion beams. In addition, we investi-gate the effect of possible imperfections on the collima-tion leakage and the power deposition in magnets.

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MOPAB013

Recent Development and Results With the Merlin Tracking Code

collimation, proton, collider, electron

104

S.C. Tygier, R.B. Appleby, H. Rafique
UMAN, Manchester, United Kingdom
R.J. Barlow, S. Rowan
IIAA, Huddersfield, United Kingdom
J. Molson
LAL, Orsay, France

Funding: Work supported by High Luminosity LHC : UK (HL-LHC-UK), grant number ST/N001621/1
MERLIN is an high performance accelerator simulation code which is used for modelling the collimation system at the LHC. It is written in extensible object-oriented C++ so new physics processes can be easily added. In this article we present recent developments needed for the Hi-Lumi LHC and future high energy colliders including FCC, such as hollow electron lenses and composite materials. We also give an overview of recent simulation work, validation against LHC data from run 1 and 2, and loss maps for Hi-Lumi LHC.

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MOPAB014

Generating Low Beta Regions With Quadrupoles for Final Muon Cooling

emittance, quadrupole, collider, betatron

107

J.G. Acosta, L.M. Cremaldi, T.L. Hart, S.J. Oliveros, D.J. Summers
UMiss, University, Mississippi, USA
D.V. Neuffer
Fermilab, Batavia, Illinois, USA

Funding: Work supported by Fermi Research Alliance, LLC under contract No. DE-AC02-07CH11359
Muon beams and colliders are rich sources of new physics, if muons can be cooled. A normalized rms transverse muon emittance of 280 microns has been achieved in simulation with short solenoids and a betatron function of 3 cm. Here we use ICOOL, G4beamline, and MAD-X to explore using a 400 MeV/c muon beam and strong focusing quadrupoles to approach a normalized transverse emittance of 100 microns and finish 6D muon cooling. The low beta regions produced by the quadrupoles are occupied by dense, low Z absorbers, such as lithium hydride or beryllium, that cool the beam. Equilibrium transverse emittance is linearly proportional to the beta function. Reverse emittance exchange with septa and/or wedges is then used to decrease transverse emittance from 100 to 25 microns at the expense of longitudinal emittance for a high energy lepton collider. Work remains to be done on chromaticity correction.

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MOPAB023

ESS Emittance Measurements at INFN CATANIA

emittance, ion, ion-source, proton

123

O. Tuske, P. Daniel-Thomas, J.F. Denis, Y. Gauthier, T.J. Joannem, N. Misiara, V. Nadot, G. Perreu, F. Senée, V. Silva
CEA/IRFU, Gif-sur-Yvette, France
L. Celona, L. Neri
INFN/LNS, Catania, Italy
B. Cheymol, T.J. Shea
ESS, Lund, Sweden
I. Chu, M. Monteremand
CEA LITEN, CEA Grenoble, Grenoble, France
Ø. Midttun
University of Bergen, Bergen, Norway
T.V. Vacher
CEA/DSM/IRFU, France

Beam characteristics at low energy are an absolute necessity for an acceptable injection in the next stage of a linear accelerator, and are also necessary to reduce beam loss and radiation inside the machine. CEA is taking part of ESS linac construction, by designing Emittance Measurement Units (EMU) for the Low Energy Beam Transport (LEBT). The EMU are designed to qualify the proton beam produced by the INFN Catania ion source. This measurement has been decided to be time resolved, allowing to follow the beam emittance reduction, during the pulse length. A 1Mhz acquisition board controlled by EPICS save raw datas to an archiver in order to be able to post process the measurements for time resolution. The design corresponds to an Allison's scanner, using entrance and exit slits, electrostatic plates and a faraday cup. The beamstopper protects the device and can be removable to fit to beam power. It has been manufactured by the CEA/LITEN with copper tungsten HIP technique. This article report the first measurements on the ESS injector at INFN CATANIA.

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MOPAB027

Preparation of CVD Diamond Detector for fast Luminosity Monitoring of SuperKEKB

luminosity, detector, monitoring, target

135

C.G. Pang, P. Bambade, D. El Khechen, D. Jehanno, V. Kubytskyi, Y. Peinaud, C. Rimbault
LAL, Orsay, France

The SuperKEKB e⁺-e⁻ collider aims to reach a very high luminosity of 8×10 ³⁵ cm'2s'1, using highly focused ultra-low emittance bunches colliding every 4ns. To meet the requirement of the dithering feedback system used to stabilize the horizontal orbit at the IP (interaction point), a relative precision of 10 '3 in 1ms is specified for the fast luminosity monitoring, which can be in principle achieved thanks to the large cross section of the radiative Bhabha process. This paper firstly presents the fraction of detected Bhabha scattering positrons with a new beam pipe arrangement coupled with a Tungsten radiator to be installed in the Low Energy Ring; Then the characteristics of signals from a sCVD diamond detector with thickness of 140'm coupled with a broadband current amplifier were studied based on tests with a Sr-90 source; Finally, simulated results for the reconstructed luminosity and the relative precision with different assumed luminosities are also reported.

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MOPAB028

Estimation of Longitudinal Dimensions of Sub-Picosecond Electron Bunches with the 3-Phase Method

booster, electron, space-charge, gun

139

H. Purwar, C. Bruni, A. Gonnin
LAL, Orsay, France
T. Vinatier
DESY, Hamburg, Germany

An estimation of the longitudinal dimensions for short electron bunches in an accelerating field is an important diagnostic and can be extremely helpful in evaluating the performance of an accelerator. We investigate a method for close estimation of bunch length for sub-picosecond electron bunches from the measurement of their energy spreads. Three or more measurements for the bunch energy spread are made by varying the phase of the accelerating structure and later a reconstruction of the bunch longitudinal dimensions, namely bunch length, initial energy spread and chirp at the entrance of the accelerating structure are obtained using the least square method. A comparison of the obtained results with ASTRA simulations is also included to validate the 3-phase method for sub-ps electron bunches. It is a simple method from both understanding (easy reconstruction using transport matrices) and experimental point of views (multiple measurements of energy spread with varying phase of the accelerating structure).

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MOPAB029

Experimental Study of Halo Formation at ATF2

vacuum, scattering, electron, detector

142

R.J. Yang, P. Bambade, A. Faus-Golfe, V. Kubytskyi, S. Wallon
LAL, Orsay, France
A. Aryshev, T. Naito
KEK, Ibaraki, Japan
N. Fuster-Martínez
IFIC, Valencia, Spain

For Accelerator Test Facility 2 (ATF2), as well as other high-intensity accelerators, beam halo has been an important aspect reducing the machine performance and activating the components. It is imperative to clearly understand the mechanisms that lead to halo formation and to test the avail- able theoretical models with an adequate experiment setup. In this paper, the experimental measurement of the beam halo formation from beam gas scattering is presented. The upgrading of an OTR/YAG screen monitor for future halo study is also introduced.

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MOPAB037

Analytical and Numerical Performance Analysis of a Cryogenic Current Comparator

damping, cryogenics, dipole, beam-diagnostic

160

N. Marsic, H. De Gersem, W.F.O. Müller
TEMF, TU Darmstadt, Darmstadt, Germany
F. Kurian, M. Schwickert, T. Sieber
GSI, Darmstadt, Germany

Funding: This research is funded by the German Bundesministerium für Bildung und Forschung as the project BMBF-05P15RDRBB Ultra-Sensitive Strahlstrommessung für zukünftige Beschleunigeranlagen.
Nowadays, cryogenic current comparators (CCCs) are among the most accurate devices for measuring extremely small electric currents. Probably the most interesting property of this equipment, is the excellent position independence of the current passing through it. This feature motivated the use of CCCs for beam instrumentation in particle accelerators. A typical CCC consists of a ferrite core, a pick-up coil, a superconducting quantum interference device, appropriate electronics and superconducting shielding consisting of a meander structure. This configuration offers a strong attenuation for all the magnetic field components, except for the azimuthal one. Thus, high precision measurements of extremely low beam currents are made possible. The damping performance of this device is analysed in this work. A 3D finite element (FE) analysis has been carried out and the computed results were compared to an analytical model*. Furthermore, in order to reduce the computation time, a 2.5D FE model is also proposed and discussed.
* K. Grohmann et al., Field attenuation as the underlying principle of
cryo-current comparators 2. Ring cavity elements, Cryogenics, vol. 16, no. 10, pp. 601-605, 1976.

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MOPAB038

Research and Development of Diamond Based Beam Monitoring and Diagnostics Systems at the S-DALINAC

detector, monitoring, FPGA, electron

163

A. Rost, T. Galatyuk
TU Darmstadt, Darmstadt, Germany
T. Galatyuk, J. Pietraszko
GSI, Darmstadt, Germany

Funding: This work has been supported by the DFG through GRK 2128 and VH-NG-823.
For future experiments with the HADES and CBM detectors at FAIR in Darmstadt, a radiation hard and fast beam detector is required. The beam detector has to perform precise T0 measurements (σ_T0 < 50 ps) and should also offer beam monitoring capabilities. These tasks can be fulfilled by utilizing single-crystal Chemical Vapor Deposition (scCVD) diamond based detectors. For research and development of such detectors, a test set-up will be installed at the Superconducting Darmstadt Electron Linear Accelerator (S-DALINAC) of TU Darmstadt. A read-out system for a beam monitoring and diagnostics system is currently under development. It is based on the already well established TRB3 platform, which can provide FPGA based signal discriminators and high precision FPGA-TDCs with on-line monitoring capabilities. In this contribution the concept and the performance of a prototype beam monitoring system will be discussed. Furthermore the preparatory work, with particular focus on the beam-line simulations, for a multipurpose beam detector test set-up at the S-DALINAC will be addressed.

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MOPAB045

Reconstruction of the 3D Charge Distribution of an Electron Bunch Using a Novel Variable-Polarization Transverse Deflecting Structure (TDS)

electron, experiment, space-charge, laser

188

D. Marx, R.W. Aßmann, U. Dorda, U. Dorda, B. Marchetti
DESY, Hamburg, Germany
P. Craievich
PSI, Villigen PSI, Switzerland
A. Grudiev, A. Grudiev, A. Grudiev
CERN, Geneva, Switzerland

A TDS is a well-known device for the characterization of the longitudinal properties of an electron bunch in a linear accelerator. So far, the correlation of the slice properties in the horizontal/vertical planes of the electron bunch distribution has been characterized by using a TDS system deflecting in the vertical/horizontal directions respectively and analysing the image on a subsequent screen*. Recently, an innovative design for a TDS structure has been proposed, which includes the possibility of continuously varying the angle of the transverse streaking field inside a TDS structure**. This allows the beam distribution to be characterized in all transverse directions. By collecting measurements of bunches streaked at different angles and combining them using tomographic techniques, it is possible to retrieve 3D distributions of the charge density. In this paper, a method is proposed and simulation results are presented to show the feasibility of such an approach at the upcoming accelerator R&D facility, SINBAD, at DESY***.
* M. Roehrs et al., Phys. Rev. ST Accel. Beams 12, 050704 (2009).
** A. Grudiev, Report No. CLIC-Note-1067, 2016.
*** B. Marchetti et al. X-band TDS project contribution to these conference proceedings.

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MOPAB048

Simulation of fs Bunch Length Determination with the 3-Phase Method and THz Dielectric Loaded Waveguides

injection, linac, space-charge, electron

199

T. Vinatier, R.W. Aßmann, U. Dorda, B. Marchetti
DESY, Hamburg, Germany

In this paper, we investigate with ASTRA simulations the capability of the 3-phase method to reconstruct the length of a fs electron bunch. We show that a standard 3 GHz travelling wave accelerating structure is not suited for this purpose, because of the too important effect of the space-charge forces and of the too small variations of the induced energy spread with the bunch injection phase. Our simulations demonstrate that the use of dielectric-loaded waveguides driven by THz pulses would allow overcoming these two limitations and possibly achieving an ultimate resolution better than 5% for the determination of a 6.25 fs rms bunch length at 100 MeV energy and 1 pC charge. The next steps of the study to better evaluate, in simulations and experiments, the possible sources of degradation of the 3-phase method resolution are also mentioned.

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MOPAB052

A Transverse Deflection Structure with Dielectric-Lined Waveguides in the Sub-THz Regime

electron, emittance, impedance, laser

215

F. Lemery
University of Hamburg, Hamburg, Germany
R.W. Aßmann, K. Flöttmann, T. Vinatier
DESY, Hamburg, Germany

Longitudinal bunch measurements are typically done with rf-powered transverse deflection structures with operating frequencies 1-12~GHz. We explore the use of mm-scale, THz-driven, dielectric-lined cylindrical waveguides as transverse deflectors by driving the fundamental deflecting mode of the structure, the HEM₁₁. We give a brief overview of the physics, history, and provide an example with a 5~MeV beam using {\sc astra} and {\sc CST-MWS}.
This work was supported by the European Research Council (ERC) under the European Union's Seventh Framework Programme (FP/2007-2013)/ERC Grant agreement no. 609920

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MOPAB053

Electron Bunch Streaking With Single-Cycle THz Radiation Using an NSOM-Style TIP

electron, laser, interaction-region, diagnostics

219

F. Lemery, A.F. Hartin
University of Hamburg, Hamburg, Germany
D. Zhang
DESY, Hamburg, Germany
D. Zhang
CFEL, Hamburg, Germany

THz wavelengths provide an excellent scale for electron-bunch acceleration and manipulation. The improvement of laser-based THz-generation efficiencies to ~1% provides a good opportunity for e.g. phase-space manipulation and diagnostics. We describe a simple technique to streak and characterize electron beams. We provide full simulation results and discuss the scaling of this technique to various regimes.

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MOPAB054

Development and Application of Rogowski Coils as Beam Position Monitors

dipole, storage-ring, instrumentation, synchrotron

223

F. Trinkel, H. Soltner
FZJ, Jülich, Germany

We have developed segmented Rogowski coils as a beam position monitors at the storage ring COSY Jülich as an alternative to the conventional monitors installed there. These coils feature a torus with two or four segments, each densely covered with an insulating copper wire of 150μm in diameter. The bunched particle beam induces voltages in these segments, which are combined and analysed to yield information about beam displacements in the horizontal and the vertical plane. We highlight our theoretical understanding of position determination of these coils together with corresponding numerical simulations. The integration of such a beam position monitor with COSY and first results with it for a bunched deuteron beam are described. The ultimate goal of this development is a better control of the beam orbit for the very demanding requirements in a future ring dedicated to the measurement of Electric Dipole Moments (EDMs) of charged particles.

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MOPAB056

4-Channel Single Shot and Turn-by-Turn Spectral Measurements of Bursting CSR

detector, radiation, synchrotron, storage-ring

231

J.L. Steinmann, E. Blomley, M. Brosi, E. Bründermann, M. Caselle, B. Kehrer, A.-S. Müller, L. Rota, M. Schuh, P. Schönfeldt, M. Siegel, M. Weber
KIT, Karlsruhe, Germany

The test facility and synchrotron radiation source ANKA at the Karlsruhe Institute of Technology (KIT) in Karlsruhe, Germany, can be operated in a short-bunch mode. Above a threshold current, the high charge density leads to microwave instabilities and the formation of sub-structures. These time-varying sub-structures on bunches of picosecond duration lead to the observation of bursting coherent synchrotron radiation (CSR) in the terahertz (THz) frequency range. The spectral information in this range contains valuable information about the bunch length, shape and sub-structures. We present recent measurements of a spectrometer setup that consists of 4 ultra-fast THz detectors, sensitive in different frequency bands, combined with the KAPTURE readout system developed at KIT for studies requiring high data throughput. This setup allows to record continuously the spectral information on a bunch-by-bunch and turn-by-turn basis. This contribution describes the potential of time-resolved spectral measurements of the short-bunch beam dynamics.

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MOPAB059

Energy Chirp Measurements by Means of an RF Deflector: a Case Study the Gamma Beam Source LINAC at ELI-NP

electron, linac, brightness, detector

242

L. Sabato
U. Sannio, Benevento, Italy
P. Arpaia, A. Liccardo
Naples University Federico II, Science and Technology Pole, Napoli, Italy
A. Mostacci, L. Palumbo
University of Rome La Sapienza, Rome, Italy
A. Variola
INFN/LNF, Frascati (Roma), Italy

RF Deflector (RFD) based measurements are widely used in high–brightness electron LINAC around the world in order to measure the ultra–short electron bunch length. The RFD provides a vertical kick to the particles of the electron bunch according to their longitudinal positions. In this paper, a measurement technique for the bunch length and other bunch proprieties, based on the usage of an RFD, is proposed. The basic idea is to obtain information about the bunch length, energy chirp, and energy spread from vertical spot size measurements varying the RFD phase, because they add contributions on this quantity. The case study is the Gamma Beam System (GBS), the Compton Source being built in the Extreme Light Infrastructure–Nuclear Physics (ELI–NP) facility. The ELEctron Generation ANd Tracking (ELEGANT) code is used for tracking the particles from RFD to the measurement screen.

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MOPAB060

Thermal Issues for the Optical Transition Radiation Screen for the ELI-NP Compton Gamma Source

electron, target, radiation, laser

246

F. Cioeta, D. Alesini, A. Falone, V.L. Lollo, L. Pellegrino, A. Variola
INFN/LNF, Frascati (Roma), Italy
M. Ciambrella
University of Rome La Sapienza, Rome, Italy
D. Cortis, M. Marongiu, V. Pettinacci
INFN-Roma, Roma, Italy
A. Mostacci, L. Palumbo
Rome University La Sapienza, Roma, Italy

A high brightness electron Linac is being built in the Compton Gamma Source at the ELI Nuclear Physics facility in Romania. To achieve the design luminosity, a train of 32 bunches, 16 ns spaced, with a nominal charge of 250 pC will collide with the laser beam in two interaction points. Electron beam spot size is measured with optical transition radiation (OTR) profile monitors. In order to measure the beam properties, the OTR screens must sustain the thermal and mechanical stress due to the energy deposited by the bunches. This paper is an ANSYS study of the issues due to the high energy transferred to the OTR screens. Thermal multicycle analysis will be shown; each analysis will be followed by a structural analysis in order to investigate the performance of the material. The multiphysics analysis will be extended to the mechanical contact areas with the target frame in order to evaluate the order of magnitude of the phenomena in those regions.

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MOPAB064

Photoinjector Emittance Measurement at STAR

emittance, gun, electron, solenoid

257

A. Bacci, C. Curatolo, I. Drebot, L. Serafini, V. Torri
Istituto Nazionale di Fisica Nucleare, Milano, Italy
R.G. Agostino, R. Barberi, V. Formoso, M. Ghedini, F. Martire, C. Pace
UNICAL, Arcavacata di Rende, Italy
D. Alesini, M. Bellaveglia, J.J. Beltrano, F.G. Bisesto, G. Borgese, B. Buonomo, G. Di Pirro, G. Di Raddo, A. Esposito, A. Gallo, A. Ghigo, F. Iungo, A. Papa, L. Pellegrino, A. Stella, C. Vaccarezza, S. Vescovi
INFN/LNF, Frascati (Roma), Italy
A. Cianchi
Università di Roma II Tor Vergata, Roma, Italy
G. D'Auria, A. Fabris, M. Marazzi
Elettra-Sincrotrone Trieste S.C.p.A., Basovizza, Italy
V. Petrillo
Universita' degli Studi di Milano, Milano, Italy
A. Policicchio
UniCal & INFN CS, Arcavacata di Rende (CS), Italy
E. Puppin
Politecnico/Milano, Milano, Italy
M. Rossetti Conti
Universita' degli Studi di Milano & INFN, Milano, Italy

STAR is an advanced Thomson source of monochromatic and tunable, ps-long, polarised X-ray beams in the 40-140 keV range. The commissioning has started at the Univ. of Calabria (Italy). The light source is driven by a high-brightness, low-emittance electron beam produced in a LINAC allowing for the source tunability and spectral density. This note reports on an emittance measurement schema based on the insertion of a slit mask in the vacuum chamber dedicated to the photocathode laser entrance. Results of the simulation of the measurement technique are reported, and the use of the data for the optimisation of the accelerator performance are detailed. The experimental setup and the application developed in EPICS for image recording and analysis are also described.

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MOPAB066

Development and Performance Test of the BPM System for the SPring-8 Upgrade

radiation, storage-ring, electron, photon

265

H. Maesaka
RIKEN SPring-8 Center, Innovative Light Sources Division, Hyogo, Japan
H. Dewa, T. Fujita, M. Masaki
JASRI, Hyogo, Japan
S. Takano
Japan Synchrotron Radiation Research Institute (JASRI), RIKEN SPring-8 Center, Hyogo, Japan

We are developing a stable and precise BPM system for the low-emittance upgrade of SPring-8. One of the essential requirements for the BPM is the long term stabilization of the photon beam by regulating the electron beam orbit. Both the single-pass resolution of 100 um rms for an injected beam charge of 100 pC and an accuracy of 100 um rms are also crucial for beam commissioning. Drift sources of the present BPM system have been investigated extensively, such as humidity-dependent drifts coming from the radiation damage of coaxial cables, and the results are fed back to the design of the new BPM system. We have optimized the design of the button BPM electrodes to reconcile reduction of trapped-mode heating and maximization of the signal intensity. Stringent machining tolerance is imposed on a BPM head to align the BPM electric center accurately. A few kinds of the BPM head prototypes were produced and the machining accuracy, RF characteristics etc. were confirmed to be sufficient. We have installed one of the prototypes in the present storage ring to test the performance of the new BPM system under development, and have been obtaining successful results satisfying the requirements.

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MOPAB069

Measurement of Transverse Multipole Moments of the Proton Beam in the J-PARC MR

quadrupole, multipole, proton, vacuum

274

T. Toyama
J-PARC, KEK & JAEA, Ibaraki-ken, Japan
A. Ichikawa, A. Minamino, K.G. Nakamura, Y. Nakanishi, T. Nakaya, W. Uno
Kyoto University, Kyoto, Japan
T. Koseki, H. Kuboki, M. Okada
KEK, Tokai, Ibaraki, Japan

Funding: This work was partially supported by MEXT/JSPS KAKENHI Grant Numbers 25105002 and 16H06288.
Transverse multipole moments (quadrupole and more) of the beam may give important informations of the beam such as beam sizes, nonlinear resonances and so on. However higher moments are difficult to measure because signal-to-noise-ratio becomes smaller proportional to the n-th order of the beam-radius-to-vacuum-duct-radius ratio. In order to increase the SNR and to extend the multipole order, we developed and installed a 16 electrode beam monitor in the J-PARC MR, which consists of guard-potential-separated 16 striplines. The calibration method, beam test results will be presented.

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MOPAB082

Design and Simulation of High Order Mode Cavity Bunch Length Monitor for Infrared Free Electron Laser

cavity, FEL, laser, electron

309

Q. Wang, X.Y. Liu, P. Lu, Q. Luo, B.G. Sun, L.L. Tang, J.H. Wei, F.F. Wu, Y.L. Yang, T.Y. Zhou, Z.R. Zhou
USTC/NSRL, Hefei, Anhui, People's Republic of China

Funding: Supported by The National Key Research and Development Program of China (2016YFA0401900, 2016YFA0401903); NSFC (11375178, 11575181); the Fundamental Research Funds for the Central Universities (WK2310000046)
A bunch length monitor using resonant cavity has been designed for the NSRL Infrared Free Electron Laser (IR-FEL) facility. To avoid the restriction of working fre-quency caused by the beam pipe radius, the high order modes of the harmonic cavities are utilized. The position and orientation of coaxial probes are optimized to avoid interference modes which come from the cavity and beam tube according to the analysis formula of electro-magnetic field distribution. Based on the parameters of IR-FEL, a simulation is performed to verify the feasibility of the bunch length monitor. The simulation result shows that the design meets the requirements of IR-FEL, and the resolution can be better than 50 fs.

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MOPAB087

Study on Supports System of BPMs for HEPs

site, factory, storage-ring, synchrotron

322

Z.Z. Wang, J.S. Cao, J. He, H.Z. Ma, Y.F. Sui, Z. Wang
IHEP, People's Republic of China

The High Energy Photon Source(HEPS), a third generation light source with the energy of 6 GeV, is under constructed at IHEP. It has an ultralow emittance (~50pm.rad) and small beam size, thus the requirement of BPM in precision and resolution is quite high. Independent supports with high degree of mechanical and thermal stability will be employed for some special BPMs, such as the BPMs near the insert devices. The supports should have high eigen-frequencies to minimize the amplification of vibration from the ground. Vibrations information of the ground around the supports also need be estimated, with which FEA (finite element analysis) had be utilized to simulate the performance of the supports. Measurements of vibrational stability of the prototype supports have be done and compared with the simulation.

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MOPAB088

A Differential Beam Intensity Monitoring for the CIADS LINAC

monitoring, linac, instrumentation, pick-up

325

Z.P. Xie
Hohai University, Nanjing, People's Republic of China
Y. He, R. Huang, Z.J. Wang
IMP/CAS, Lanzhou, People's Republic of China

Funding: Work supported by the National Natural Science Foundation of China (Grant No. 91026001) and the Fundamental Research Funds for the Chinese Central Universities
The high power Linac places many crucial requirements on the beam diagnostics for the China initiative accelerator driven subcritical(CIADS) facility. Measuring the beam loss is essential for the purpose of machine protections for the facility. A beam position pickup based differential beam current monitoring (BPDBCM) scheme has been proposed for the MEBT section at CIADS. Discussions of the principles for the scheme and the realtionship between beam intensity measurement and the pulse length are presented. Simulations are performed and they demonstrate that the proposed system can be effective at the low enery section for the CIADS beam. This paper describes the proposed implementation that will have the capability of detecting both the instantaneous and chronicle loss in real time.

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MOPAB090

Wavefront Distortion Measurement at SSRF

experiment, radiation, synchrotron, synchrotron-radiation

332

B. Gao, H.J. Chen, J. Chen, Y.B. Leng, K.R. Ye
SINAP, Shanghai, People's Republic of China
B. Gao
University of Chinese Academy of Sciences, Beijing, People's Republic of China
N. Zhang
SSRF, Shanghai, People's Republic of China

The Synchrotron Radiation Monitor (SRM) system has been designed and constructed at the Shanghai synchrotron radiation Facility (SSRF) for several years and runs good. However, the monitor extraction mirror deformation is quite common at different facilities, and other reflecting mirrors in the optic path also have surface error and angle error. As we decide to upgrade the SR monitor system at SSRF, this issue is also one of the most import thing what we should overcome. In order to verify the feasibility and evaluate the accuracy, simulations based on SRW code have been done. In this simulation, a dedicated algorithm was developed to reconstruct wavefront. The result and the algorithm is very useful for our experiment and upgrade program. In this paper, the algorithm and the experiments based on Shark-Hartmann wavefront sensor will be presented detailed.

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MOPAB093

Bunch Phase Measurement for Storage Ring

storage-ring, injection, experiment, pick-up

341

Y.M. Zhou, Y.B. Leng, N. Zhang
SSRF, Shanghai, People's Republic of China
H.J. Chen
SINAP, Shanghai, People's Republic of China

A bunch-by-bunch phase measurement system has been studied to improve the accuracy of phase measurement. Longitudinal phase information will be retrieved from beam signals picked up from the button electrodes. The signals from four electrodes in the BPM are summed by using a 4-way power driver, by which the effect of the transverse beam offset on the phase measurement can be eliminated. Four samples with fixed time interval (typical 100ps) for each bunch, which are taken by a 500MHz waveform recorder with a four channels signal splitting and delaying network, will be used to calculate bunch phase. In this paper, we present the layout of the system and primary experimental results.

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MOPAB095

Development of the Simulation Software Package for the CBPM System

cavity, network, FEL, experiment

349

J. Chen, L.W. Lai, Y.B. Leng, L.Y. Yu
SINAP, Shanghai, People's Republic of China
N. Zhang
SSRF, Shanghai, People's Republic of China

In recent years, the development and construction of Free Electron Laser (FEL) facilities are in full swing. For FEL facilities, to generate coherent X-ray, cavity beam position monitor (CBPM) system which consist of cavity BPM, RF front-end and signal processor are employed to measure the transverse position in the undulator section. A generic simulation software package, with the S21 parameters of the real components, for the design of the RF front-end and the optimize of the CBPM system was developed. In this paper, the development of the generic simulation software package, and the experiment results with beam at Shanghai Deep ultraviolet (SDUV) FEL facility to verify the correctness of the simulation soft package will be introduced. The application in the design and optimize of the RF front-end for the Dalian Coherent Source (DCLS) will be addressed as well .

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MOPAB099

Design Study of Drift Tube Linac for BNCT Accelerator

DTL, quadrupole, rfq, linac

359

Y. Lee, S.W. Jang, E.-S. Kim
Korea University Sejong Campus, Sejong, Republic of Korea
B.H. Choi
IBS, Daejeon, Republic of Korea
D.S. Kim
Dawonsys, Siheung-City, Republic of Korea
Z. Li
SCU, Chengdu, People's Republic of China

A-BNCT accelerator is being developed as a proton accelerator with a high beam current of 50 mA for effective cancer therapy. Drift tube linac (DTL) with the length of 4.5 m is composed of 1 tank and 48 drift tubes (DTs). Proton beam is accelerated from 3 MeV to 10 MeV. Electromagnetic quadrupoles (EMQs) are inserted into every DT for transverse focusing. Slug tuners and post couplers (PCs) are used for accelerating field stabilization and resonant frequency tuning, respectively. The beam dynamics and engineering design for the DTL are performed for effective beam acceleration, and the design results are in detail presented.

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MOPAB107

A Method for Determining the Roll Angle of the CLIC Accelerating Structures From the Beam Shape Downstream of the Structure

octupole, collider, experiment, emittance

368

J. Ögren, V.G. Ziemann
Uppsala University, Uppsala, Sweden
W. Farabolini
CEA/DSM/IRFU, France

The Compact Linear Collider (CLIC) accelerating structures have a four-fold symmetry from the radial waveguides for damping higher order modes. This symmetry allows for an octupole component of the rf fields to co-propagate with the main accelerating field. The effect of this octupole mode has been observed at the CLIC test facility 3. In CLIC the accelerating structures are mounted together on a moveable girders. There are four vertical and four horizontal actuators on the girder, which allows for 5D control in a limited range and for instance we can roll the girder. By observing the beam shape perturbed by the octupole field on a screen downstream from the structure we can determine the roll angle and thus align the structure azimuthally. Here we discuss a possible method and show some preliminary results.

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MOPAB109

Operational Experience with Luminosity Scans for Beam Size Estimation in 2016 LHC Proton Physics Operation

emittance, luminosity, operation, proton

374

M. Hostettler
LHEP, Bern, Switzerland
K. Fuchsberger, G. Papotti
CERN, Geneva, Switzerland

Luminosity scans were regularly performed at the CERN Large Hadron Collider (LHC) as of 2015 as a complementary method for measuring the beam size. The CMS experiment provides bunch-by-bunch luminosities at sufficient rates to allow evaluation of bunch-by-bunch beam sizes, and the scans are performed in the horizontal and vertical plane separately. Closed orbit differences between bunches can also be derived by this analysis. During 2016 LHC operation, these scans were also done in an automated manner on a regular basis, and the analysis was improved to significantly reduce the systematic uncertainty, especially in the crossing plane. This contribution first highlights the recent improvements to the analysis and elaborates on their impact. The measured beam sizes during 2016 proton physics operation are then shown and compared to measurements from synchrotron light telescopes and estimates based on the absolute luminosities of the LHC experiments.

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MOPAB111

Diffraction Radiation for Non-Invasive, High-Resolution Beam Size Measurements in Future Linear Colliders

target, radiation, collider, polarization

381

M. Bergamaschi, R. Kieffer, T. Lefèvre, S. Mazzoni
CERN, Geneva, Switzerland
A. Aryshev, N. Terunuma
KEK, Ibaraki, Japan
M. Bergamaschi, P. Karataev, K.O. Kruchinin
JAI, Egham, Surrey, United Kingdom
M. Bergamaschi, P. Karataev, K.O. Kruchinin
Royal Holloway, University of London, Surrey, United Kingdom

Next generation linear colliders such as the Compact Linear Collider (CLIC) or the International Linear Collider (ILC) will accelerate particle beams with extremely small emittance. The high current and small size of the beam (micron-scale) due to such small emittance require non-invasive, high-resolution techniques for beam diagnostics. Diffraction Radiation (DR), a polarization radiation that appears when a charged particle moves in the vicinity of a medium, is an ideal candidate being non-invasive and allowing beams as small as a few tens of microns to be measured. Since DR is sensitive to beam parameters other than the transverse profile (e.g. its divergence and position), preparatory simulations have been performed with realistic beam parameters. A new dedicated instrument was installed in the KEK-ATF2 beam line in February 2016. At present DR is observed in the visible wavelength range, with an upgrade to the ultraviolet (200nm) planned for spring 2017 to optimize sensitivity to smaller beam sizes. Presented here are the latest results of these DR beam size measurements and simulations.

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MOPAB127

A New Method for Emittance Reconstruction Using a Scraper in a Dispersive Region of a Low Energy Storage Ring

emittance, storage-ring, antiproton, closed-orbit

429

J.R. Hunt, J. Resta-López, C.P. Welsch
The University of Liverpool, Liverpool, United Kingdom
C. Carli
CERN, Geneva, Switzerland
J.R. Hunt, J. Resta-López, C.P. Welsch
Cockcroft Institute, Warrington, Cheshire, United Kingdom

Funding: Science and Technology Funding Council, UK CERN
Beam scraping is a standard method for beam emittance measurements at low energies and will be applied at the Extra Low ENergy Antimatter (ELENA) ring. However, in ELENA, as in many other low energy storage rings, the scraper is located in a position of finite dispersion which poses a unique challenge when reconstructing the emittance from beam intensity data. A new algorithm for ELENA and other machines that use a scraper in a dispersive region has been developed. It combines data obtained by scraping the beam from opposite sides with information on the storage ring lattice. In this contribution, the new algorithm is presented, tested using simulations and compared with alternate methods for emittance reconstruction.

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MOPAB137

Validation of a Novel Emittance Diagnostic Method for Beams with Significant Space Charge

emittance, space-charge, focusing, quadrupole

451

R.B. Fiorito, C.P. Welsch, H.D. Zhang
Cockcroft Institute, Warrington, Cheshire, United Kingdom
M.E. Conde, N.R. Neveu, J.F. Power
ANL, Argonne, Illinois, USA
O. Mete Apsimon
Cockcroft Institute, Lancaster University, Lancaster, United Kingdom
A.G. Shkvarunets
UMD, College Park, Maryland, USA

Funding: Work supported by the EU under grant agreement 624890, the STFC Cockcroft Institute Core Grant No. ST/G008248/1.
Exact knowledge of beam emittance is of central importance for essentially every accelerator. However, there are only few methods to determine it when the beam has significant space charge. We report on our progress to validate a novel diagnostic method that has been proposed to determine the RMS emittance of an electron beam with space charge. This method uses RMS divergence and beam size data measured at a screen placed in a free drift region for selected values of magnetic focusing strength. A novel algorithm is then used to determine the cross correlation term and consequently the RMS emittance of the beam. Simulations, quadrupole scans, phase space tomography and optical diffraction-dielectric foil radiation interferometry are currently being employed to determine and compare the horizontal (x) and vertical (y) emittances of the 14 MeV witness electron beam at Argonne National Laboratory's Wakefield Accelerator. The results of simulations and current measurements are presented and the advantages of the new technique are discussed.

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MOPAB138

Comparison of Optical Transition Radiation Simulations and Theory

radiation, diagnostics, optics, electron

455

J. Wolfenden, R.B. Fiorito, C.P. Welsch
Cockcroft Institute, Warrington, Cheshire, United Kingdom
M. Bergamaschi, P. Karataev, K.O. Kruchinin
JAI, Egham, Surrey, United Kingdom
M. Bergamaschi, P. Karataev, K.O. Kruchinin
Royal Holloway, University of London, Surrey, United Kingdom
M. Bergamaschi, R. Kieffer, T. Lefèvre
CERN, Geneva, Switzerland
R.B. Fiorito, C.P. Welsch, J. Wolfenden
The University of Liverpool, Liverpool, United Kingdom

The majority of optical diagnostics currently used will not stand up to the requirements of the next generation of particle accelerators. Current methodologies need innovation to be able to reach the sub-micrometre resolution and sensitivity that will be required. One technique that has the potential to meet these requirements is optical transition radiation (OTR) imaging. A new algorithm is proposed which incorporates OTR theory, optical effects and beam distribution. This algorithm takes an existing method used for beam imaging and pushes the limits resolution beyond that normally attainable. In doing so, it can provide a reliable and economical diagnostic for future accelerators. A discussion on further applications of the algorithm is also presented.

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MOPAB141

Instrumentation and Its Interaction With the Secondary Beam for the Fermilab Muon Campus

ion, experiment, vacuum, emittance

466

D. Stratakis, B.E. Drendel, M.J. Syphers
Fermilab, Batavia, Illinois, USA
M.J. Syphers
Northern Illinois University, DeKalb, Illinois, USA

Funding: Operated by Fermi Research Alliance, LLC under Contract No. De-AC02-07CH11359 with the United States Department of Energy.
The Fermilab Muon Campus will host the Muon g-2 experiment - a world class experiment dedicated to the search for signals of new physics. Strict demands are placed on the beam diagnostics in order to ensure delivery of high quality beams to the storage ring with minimal losses. In this study, we briefly describe the available secondary beam diagnostics for the Fermilab Muon Campus. Then, with the aid of numerical simulations we detail their interaction with the secondary beam. Finally, we compare our results against theoretical findings.

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MOPIK006

Characterization of the Electron Beam from the Thz Driven Gun for AXSIS

electron, gun, experiment, diagnostics

509

G. Vashchenko, R.W. Aßmann, U. Dorda, K. Galaydych, B. Marchetti, T. Vinatier
DESY, Hamburg, Germany
M. Fakhari, A. Fallahi, F.X. Kärtner, N.H. Matlis
CFEL, Hamburg, Germany
W. Qiao, C. Zhou
University of Hamburg, Hamburg, Germany

Funding: The research leading to these results has received funding from the European Research Council under the European Union's Seventh Framework Programme (FP/2007-2013) / ERC Grant Agreement n. 609920
The AXSIS (Attosecond X-ray Science: Imaging and Spectroscopy) project aims for development of a compact, fully coherent, THz-driven, attosecond X-ray source. A compact THz driven gun was developed, produced and tested as a source of the ultra-short electron bunches required for the project. To characterize the low energy, low-charge beam produced by such a gun tailored diagnostic devices were developed and commissioned at a test-stand chamber in CFEL (DESY). Results of the first experiments on the production and characterization of the electron beam are presented.

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MOPIK008

Numerical Studies on a Modified Cathode Tip for the ELBE Superconducting RF Gun

electron, cathode, SRF, gun

515

E.T. Tulu, U. van Rienen
Rostock University, Faculty of Computer Science and Electrical Engineering, Rostock, Germany
A. Arnold
HZDR, Dresden, Germany

Future light sources such as synchrotron radiation sources driven by an Energy Recovery Linac (ERL), Free Electron Laser (FEL) or THz radiation sources have in common that they require injectors, which provide high-brilliance, high-current electron beams in almost continuous operation. Thus, the development of appropriate highly brilliant electron sources is a central factor. A promising approach for this key component is provided by superconducting radiofrequency photoinjectors (SRF guns) [*]. Since 2007, the free-electron laser FELBE at HZDR successfully operates such a SRF gun under real conditions and equipped with all components [**]. Nevertheless, there are limitations caused by multipacting which should be overcome in order to further improve the gun [***]. One aspect in order to reach this aim lies in studying various modifications of the cathode tip [****]. This contribution will present the effectiveness of isosceles triangular grooves with respect to MP.
* Arnold, et al., NIM A, 593, 57, (2008).
** J. Teichert, et al., 2008 NSS/MIC, Dresden, Germany.
*** J. Teichert, et al., J. Phys.: Conf. Ser. 298(2011), 012008.
**** E. T. Tulu, et al., IPAC2014, p652, Dresden, Germany.

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MOPIK009

Characterization of Cold Model Cavity for Cryocooled C-Band 2.6-Cell Photocathode RF Gun at 20 K

cavity, gun, experiment, cryogenics

518

T. Tanaka, K. Hayakawa, Y. Hayakawa, K. Nakao, K. Nogami, T. Sakai, K. Takatsuka
LEBRA, Funabashi, Japan
M.K. Fukuda, D. Satoh, T. Takatomi, N. Terunuma, J. Urakawa, M. Yoshida
KEK, Ibaraki, Japan

Funding: This work was partly supported by the Photon and Quantum Basic Research Coordinated Development Program of the Japanese Ministry of Education, Culture, Sports, Science, and Technology (MEXT).
A cryocooled C-band 2.6-cell photocathode RF electron gun has been studied at Nihon University in cooperation with KEK. The cold model cavity with an input coupler was completed in spring 2016. The RF characteristics measured at room temperature were in agreement with the prediction by the CST Studio simulation. The RF characteristics at 20 K have been measured using a rather simple cavity-cooling vacuum system that was built by using existing components for tentative experiments. A thin-wall stainless-steel R48 waveguide with copper-plated inner walls has been used for the RF power transmission from the room-temperature input port to the 20-K cooled coupler waveguide. The unloaded Q-value of 73000 has been obtained by the reflection coefficient measurement at 20 K, which is in agreement with the result of the CST Studio simulation using the cavity surface resistance predicted by the theory of the anomalous skin effect.

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MOPIK016

Sub-Picosecond Beam Production for External Injection Into Plasma Experiments

gun, plasma, electron, linac

531

O. Mete Apsimon, R. Apsimon, G. Burt
Cockcroft Institute, Lancaster University, Lancaster, United Kingdom
G.X. Xia
UMAN, Manchester, United Kingdom

Funding: This work has been funded by STFC.
Applications of plasmas in accelerators benefit from short probe bunches comparable to plasma wavelength due to currently achievable plasma wake profiles. In plasma acceleration case, high capture efficiency within a narrow energy spectrum can be achieved when a sub-picosecond to femtosecond witness bunch injected behind the driver pulse at the high electric field region. A start-to-end simulation study was performed for parametric optimisation of an rf photoinjector to provide a short witness bunch for plasma applications in accelerators. An rf photoinjector is a laser-driven, high brightness and robust electron source that can provide stability and flexibility provided by today's advanced laser and rf technologies.

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MOPIK021

Generation of Transversely Segmented Beam Using a Nano-Patterned Photocathode

cathode, laser, gun, acceleration

545

A. Lueangaramwong, P. Piot
Northern Illinois University, DeKalb, Illinois, USA
G. Andonian
RadiaBeam, Santa Monica, California, USA
P. Piot
Fermilab, Batavia, Illinois, USA

Funding: Work supported by US Department of Energy (DOE) contract DE-SC0009656 with Radiabeam Technologies and by NSF grant PHY-1535401 with Northern Illinois University.
Plasmonic photocathodes – nano-patterned photocathodes with periodicity comparable to the excitation laser – have demonstrated enhanced quantum efficiency. In the present paper we present numerical simulations of the beam dynamics associated to the emission process from this type of cathodes and to the subsequent acceleration to relativistic energies by combining WARP and IMPACT-T programs. We especially consider the possibility to transversely image the cathode surface at high energy and enable the generation of transversely segment beams.

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MOPIK023

Cornell Laboratory for High Intensity, Ultra-Bright and Polarized Electron Beams

electron, gun, cathode, ion

551

L. Cultrera, A.C. Bartnik, I.V. Bazarov, C.M. Gulliford, P. Gupta, H. Lee, S.A. McBride, T.P. Moore
Cornell University (CLASSE), Cornell Laboratory for Accelerator-Based Sciences and Education, Ithaca, New York, USA

Funding: This work has been funded by the National Science Foundation (Grant No. PHY-1416318) and Department of Energy (Grants No. DE-SC0014338, No. DE-SC0011643 and No. DE-SC0016203).
We report on the current activities pursued at Cornell University for the production of electron beams tailored to a wide range of applications. We have developed the expertise to grow many different type of high quantum efficiency photocathode belonging to the alkali antimonide family. Those materials are ideal candidates to produce high intensity beam with average currents in the mA range. When operated near threshold at cryogenic temperature in transmission mode they can also generate the electron beams needed to perform ultrafast electron diffraction of bio molecules. We have recently expanded our facility with a Mott polarimeter to include the capability to measure polarization of the electron beam. The photocathode lab is being complemented by a dedicated photo-gun laboratory to test the photocathode properties in a real environment and to perform measurement of the beam properties under new and yet unexplored operating conditions.

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MOPIK028

Simulation Study of Halo Collimation in the TRIUMF Ariel Proton Beam Line

proton, collimation, scattering, cyclotron

557

F.W. Jones, R.A. Baartman, I.V. Bylinskii, Y.-N. Rao
TRIUMF, Vancouver, Canada

Funding: Funded under a contribution agreement with NRC (National Research Council of Canada). Capital funding from CFI (Canada Foundation for Innovation).
The TRIUMF 500 MeV H⁻ cyclotron uses stripping foil extraction to drive several proton beam lines serving different experimental programs. As part of TRIUMF's Ariel facility now under construction, a new proton beam line 4-North will be installed to transport up to 100 microamps of 480 MeV protons to an ISOL target station for rare isotope beam production. This beam line has been designed for low-loss (< 1nA/m) operation and provides space for a collimator to remove the beam halo produced by large-angle scattering in the cyclotron extraction foil. We have studied proton loss patterns and collimation efficiency using simulation codes: the older REVMOC program and a fully 3D simulation based on Geant4, with all particle interactions in matter included. Scattering in the foil is treated by a separate iterated single-scatter model. Using these tools we arrive at a prototype design for an effective collimator.

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MOPIK039

Transport Channel of Secondary Ion Beam of Experimental Setup for Selective Laser Ionization With Gas Cell Gals

ion, quadrupole, target, neutron

589

N.Yu. Kazarinov, V. Bashevoy, G.G. Gulbekyan, I.A. Ivanenko, V.I. Kazacha, N.F. Osipov
JINR, Dubna, Moscow Region, Russia
S.G. Zemlyanoy
JINR/FLNR, Moscow region, Russia

GALS is the experimental setup intended for production and research of isobaric- and isotopically pure heavy neutron-rich nuclei. The beam line consists of two parts. The initial part is used for transport of the primary 136Xe ion beam with energy of 4.5-9.0 MeV/amu from the FLNR cyclotron U400M to the Pb target for the production of the studying ion beams. These beams have the following design parameters: the charge Z = +1, the mass A = 180-270 and the kinetic energy W = 40 keV. The second part placed after the target consists of SPIG (QPIG) system, the accelerating gap, the electrostatic Einzel lens, 90-degree spectrometric magnet (calculated value of the mass-resolution is equal to 1400) and the channel for the transportation of the ions from the focal plane of the magnet to a particle detector. The results of the simulation of particle dynamics and the basic parameters of the elements of the beam lines are presented in this report.

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MOPIK044

The Use of a Passive Scatterer for SPS Slow Extraction Beam Loss Reduction

scattering, extraction, septum, proton

607

B. Goddard, B. Balhan, J.C.C.M. Borburgh, M.A. Fraser, L.S. Stoel, F.M. Velotti
CERN, Geneva, Switzerland

A significant reduction in the fraction of protons lost on the SPS electrostatic septum ES during resonant slow extraction is highly desirable for present Fixed-Target beam operation, and will become mandatory for the proposed SHiP experiment, which is now being studied in the framework of CERN's Physics Beyond Colliders program. In this paper the possible use of a passive scattering device (diffuser) is investigated. The physics processes underlying the use of a diffuser are described, and the dependence on the diffuser geometry, material and location of the potential loss reduction on the electrostatic septum (ES) wires is investigated with a semi-analytical approach. Numerical simulations to quantify the expected performance gain for the optimum configuration are presented, and the results discussed in view of the feasibility of a potential realisation in the SPS.

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MOPIK045

SPS Slow Extraction Losses and Activation: Challenges and Possibilities for Improvement

extraction, proton, radioactivity, target

611

M.A. Fraser, B. Balhan, H. Bartosik, C. Bertone, D. Björkman, J.C.C.M. Borburgh, N. Conan, K. Cornelis, R. Garcia Alia, L. Gatignon, B. Goddard, Y. Kadi, V. Kain, A. Mereghetti, F. Roncarolo, P.M. Schicho, J. Spanggaard, O. Stein, L.S. Stoel, F.M. Velotti, H. Vincke
CERN, Geneva, Switzerland

In 2015 the highest integrated number of protons in the history of the North Area was slow extracted from the CERN Super Proton Synchrotron (SPS) for the Fixed Target physics programme. At well over 1.10¹⁹ protons on target (POT), this represented the highest annual figure at SPS for almost two decades, since the West Area Neutrino Facility was operational some 20 years ago. The high intensity POT requests have continued into 2016-17 and look set to do so for the foreseeable future, especially in view of the proposed SPS Beam Dump Facility and experiments, e.g. SHiP*, which are requesting up to 4·10¹⁹ POT per year. Without significant improvements, the attainable annual POT will be limited to well below the total the SPS machine could deliver, due to activation of accelerator equipment and associated personnel dose limitations. In this contribution, the issues arising from the recent high activation levels are discussed along with the steps taken to understand, manage and mitigate these issues. The research avenues being actively pursued to improve the slow extraction related beam loss for present operation and future requests are outlined, and their relative merits discussed.
*A. Golutvin et al., ‘‘A Facility to Search for Hidden Particles (SHiP) at the CERN SPS'', CERN, Geneva, Switzerland, Rep. CERN-SPSC-2015-016 (SPSC-P-350), Apr. 2015.

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MOPIK046

Phase Space Folding Studies for Beam Loss Reduction During Resonant Slow Extraction at the CERN SPS

extraction, multipole, sextupole, proton

615

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

The requested number of protons slow-extracted from the CERN Super Proton Synchrotron (SPS) for Fixed Target (FT) physics is expected to continue increasing in the coming years, especially if the proposed SPS Beam Dump Facility is realised. Limits on the extracted intensity are already being considered to mitigate the dose to personnel during interventions required to maintain the extraction equipment, especially the electrostatic extraction septum. In addition to other on-going studies and technical developments, a reduction of the beam loss per extracted proton will play a crucial role in the future performance reach of the FT experimental programme at the SPS. In this paper a concept is investigated to reduce the fraction of beam impacting the extraction septum by folding the arm of the phase space separatrix. Beam dynamics simulations for the concept are presented and compared to the phase space acceptance of the extraction channel. The performance potential of the concept at SPS is evaluated and discussed alongside the necessary changes to the non-linear optical elements in the machine.

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MOPIK050

Reduction of Resonant Slow Extraction Losses with Shadowing of Septum Wires by a Bent Crystal

extraction, proton, collimation, septum

631

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

A new experiment, SHiP, is being studied at CERN to investigate the existence of three Heavy Neutral Leptons in order to give experimental proof to the proposed neutrino minimal Standard Model. High-intensity slow-extraction of protons from the SPS is a pre-requisite for SHiP. The experiment requires a resonant extraction with in a 7.2 s cycle, and about 4·10¹³ protons extracted at 400 GeV in a 1 s flat-top, to achieve the needed 2·10²⁰ protons on target in five years. Although the SPS has delivered this in the past to the CNGS experiment with fast extraction, for SHiP beam losses and activation of the SPS electrostatic extraction septum (ZS) could be a serious performance limitation, since the target number of protons to resonantly extract per year is a factor of two higher than ever achieved before and a factor of four than ever reached with the third-integer slow extraction. In this paper, a novel extraction technique to significantly reduce the losses at the ZS is proposed, based on the use of a bent crystal to shadow the septum wires. Theoretical concepts are developed, the performance gain quantified and a possible layout proposed.

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MOPIK055

Beam by Design: Current Pulse Shaping Through Longitudinal Dispersion Control

electron, sextupole, synchrotron, laser

644

T.K. Charles, D.M. Paganin
Monash University, Faculty of Science, Clayton, Victoria, Australia
M.J. Boland
The University of Melbourne, Melbourne, Victoria, Australia
M.J. Boland, R.T. Dowd
SLSA, Clayton, Australia

Electron beams traversing a dispersive region, such as a bunch compressor and some transport line can form caustic lines and surfaces corresponding to regions of maximum electron density, which influence the current pulse shape. In this paper, we present a technique to manipulate the longitudinal phase space distribution to achieve an arbitrary, desired current pulse shape. We show how sextupole magnets (and in certain circumstances, octupole magnets), placed within a dispersive region can be used to generate the conditions required for a flexible technique of current pulse shaping that avoids truncation through collimation.

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MOPIK057

Strategy of Beam Tuning Implementation for the SARAF MEBT and SC Linac

linac, solenoid, quadrupole, focusing

652

P.A.P. Nghiem, D. Uriot
CEA/DSM/IRFU, France
B. Dalena, J. Dumas, N. Pichoff
CEA/IRFU, Gif-sur-Yvette, France

Beam dynamics of the MEBT and Superconducting Linac in the SARAF accelerator are being finalized. A strategy for beam tuning implementation is applied to this section, leading to specifying the complete set of error tolerances / beam measurements / correctors. A systematic and precise methodology in several steps is applied, leading to fairly distributing the error budget, from which correction schemes are studied, allowing to determine the necessary beam measurements and correctors.

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MOPIK058

Beam Dynamic Studies for the SARAF MEBT and SC Linac

quadrupole, linac, cavity, rfq

655

J. Dumas, N. Pichoff, D. Uriot
CEA/IRFU, Gif-sur-Yvette, France
P.A.P. Nghiem
CEA/DSM/IRFU, France

The SARAF MEBT and Super Conducting Linac (SCL) transport and accelerate deuterons or protons from the RFQ to the final energy. In this report, beam dynamics studies for this section are described. A rational distribution of the different roles of the MEBT leads to defining its necessary quadrupole/rebuncher composition. This allows easy beam re-tuning following changes from the RFQ or the SC Linac. After observing evidences of beam losses mainly due to phase unhooking, efforts have been dedicated to enlarge the SCL longitudinal acceptance. A combination of cavity field phases is found so that the required final beam energy is also fulfilled.

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MOPIK075

Design, Simulation and Compare of Flat Cathode Electron Guns with Spherical Cathode Electron Guns for Industrial Accelerators

cathode, gun, electron, space-charge

702

M. Nazari, F. Abbasi
Shahid Beheshti University, Tehran, Iran
S. Ahmadiannamin
ILSF, Tehran, Iran
F. Ghasemi
NSTRI, Tehran, Iran
S. Haghtalab
IPM, Tehran, Iran

In this article, electron guns with flat and spherical cathodes have been designed and simulated for industrial accelerators. After checking the different features of each cathode geometry, there has been discussed about optimum values of this features. The most important features in selecting the best cathode geometry for industrial accelerators are beam waist radius, beam waist position, current density and price. Finally after comparing the different features of both geometries with each other, suitable geometry was selected.

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MOPIK076

Optimization of Dynamic Aperture with Constraints on Linear Chromaticity

luminosity, sextupole, coupling, lattice

705

H. Sugimoto, H. Koiso, A. Morita, Y. Ohnishi, K. Oide, D. Zhou
KEK, Ibaraki, Japan

This paper presents numerical technique to optimize dynamic aperture with constraints on linear chromaticity of optical functions. By solving a set of linear equations at each iteration step of dynamic aperture optimization, the linear chromaticity is kept unchanged. The variable range of tuning knobs is taken into account in order to make the technique applicable to practical use. Numerical simulations assuming the SuperKEKB design lattice are performed, and it is demonstrated that the dynamic aperture obtained with the presented scheme is almost comparable to that without constraints. Luminosity simulations assuming weak-strong model show that the constraints lead to improvements of luminosity performance.

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MOPIK078

Narrow-Band, Wide-Range Tuneable THz Source Based on the Slotted-Foil Technique

undulator, electron, radiation, FEL

712

J. Pfingstner, E. Adli, H. Holmestad
University of Oslo, Oslo, Norway
S. Bettoni, S. Reiche
PSI, Villigen PSI, Switzerland

The FEL user community has expressed a strong interest in a THz source for the excitation of their samples in pump probe experiments. The demanded THz properties are challenging to achieve, as they include a narrow bandwidth of <5-10%, the possibility of frequency tuning between 1 and 20 THz, a THz pulse energy of about 100 uJ, and a fixed phase relation from shot-to-shot. To fulfil these specifications, an accelerator-based source is proposed in this paper. It utilises the slotted-foil technique to create a pre-bunched electron beam that is injected into a helical undulator. Detailed simulation studies presented in this paper show that the corresponding undulator radiation has the demanded properties.

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MOPIK081

Study of HEPS Performance with Error Model and Simulated Correction

optics, quadrupole, sextupole, closed-orbit

721

D. Ji, Z. Duan, S.K. Tian, Y. Wei
IHEP, Beijing, People's Republic of China

As an important component of physics study on High Energy Photon Source (HEPS), error modelling and simu-lated correction will provide the guideline to restrict the manufacture redundancy of the hardware and estimate the real machine performance. In this paper, we present some work on error effect evaluation and simulated commis-sioning based on a recent lattice design.

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MOPIK087

Development of a Tune Knob for the HLS-II Storage Ring

quadrupole, storage-ring, lattice, sextupole

730

S.W. Wang, J.Y. Li, W.B. Wu, W. Xu, K. Xuan, X. Zhou
USTC/NSRL, Hefei, Anhui, People's Republic of China

A tune knob is a useful tool for lattice setup and machine studies in a storage ring. It is used to adjust the transverse tunes with a small impact on the beam dynamics. A global tune knob is designed for the Hefei Light Source (HLS). In the tune knob, the quadrupoles are grouped into four families and are symmetrically adjusted. Methodical Accelerator Design-X (MAD-X) is used to calculate the coefficients of the tune knob and the Accelerator Toolbox (AT) is used to double check the accuracy of the tune knob. The chromaticity is corrected by the sextupoles in the storage ring. This paper reports preliminary simulation results of the tune knob for HLS. The beta function deviations are also studied.

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MOPIK092

Computer Modelling of the SC202 Superconducting Cyclotron for Hadron Therapy

cyclotron, extraction, resonance, proton

742

O. Karamyshev, V. Malinin, D.V. Popov
JINR/DLNP, Dubna, Moscow region, Russia
Y.F. Bi, G. Chen, K.Z. Ding, Y. Song
ASIPP, Hefei, People's Republic of China
G.A. Karamysheva, N.A. Morozov, E.V. Samsonov, G. Shirkov, S.G. Shirkov
JINR, Dubna, Moscow Region, Russia

The SC202 superconducting cyclotron for hadron therapy is under development by collaboration of ASIPP (Hefei, China) and JINR (Dubna, Russia). The accelerator will provide about 200 MeV proton beam with maximum current of 1μA in 2017-2018. We have performed simulations of all systems of the SC202 cyclotron and specified the main parameters of magnet, acceleration system and extraction elements.

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MOPIK096

Predictability of the Beam Quality During RFQ Voltage Tuning

emittance, rfq, distributed, quadrupole

748

A. Ponton
ESS, Lund, Sweden
A.C. France
CEA/IRFU, Gif-sur-Yvette, France

It has previously been demonstrated that certain spatial harmonics of the dipolar and quadrupolar components of the RFQ voltage have stronger effects on the beam quality than others*. The study suggested that, during the tuning process to compensate for manufacturing errors, some harmonic contents (other than the first ones) should be minimized. The analysis presented in this paper looks at how we can predict the beam quality knowing the content of each voltage harmonics. We propose also a strategy to minimize the impacts of the voltage errors on the output beam phase space during the tuning phase.
* A. Ponton, A.C. France, Y.I. Levinsen, O. Piquet, B. Pottin, and E. Sargsyan, Voltage Error Studies in the ESS RFQ, in Proc. 7th International Particle Accelerator Conference (IPAC'16), Busan, Korea, May 2016, paper THPMB039, pp. 3320-3323, ISBN: 978-3-95450-147-2

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MOPIK104

Top-Up Injection With Anti-Septum

septum, injection, kicker, storage-ring

774

C.H. Gough, M. Aiba
PSI, Villigen PSI, Switzerland

We present a novel improvement for injection into the very restricted machine aperture of future light source synchrotrons. A conventional injection scheme is based on a septum to deflect the injected bunch plus a fast pulsed three or four kicker bump to bring the stored beam close to the septum wall. With the novel improvement, the bump kickers are fitted with a thin wall longitudinal metal plate which screens the injected bunch from deflection without changing the stored beam bump behaviour. This metal screen then forms the final septum, but inverted in function of the conventional approach, hence the name anti-septum. The approach does not remove the need for the main septum magnet, but for modest cost it permits the injected bunch to be brought closer to the stored beam. Application of the anti-septum to the SLS-2 project and simulation results on a prototype are presented.

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MOPIK107

Injection Efficiency Simulation in the Electron Storage Ring of X-Ray Generator NESTOR

storage-ring, injection, electron, alignment

784

A.Y. Zelinsky, P. Gladkikh, A.A. Kalamayko
NSC/KIPT, Kharkov, Ukraine

In the paper the results of the beam dynamics and injection efficiency simulation in the storage ring of the X-ray generator NESTOR are presented.

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MOPIK108

Tuning Simulations for the CLIC Traditional Beam Delivery System

luminosity, lattice, collider, linear-collider

788

R.M. Bodenstein, P. Burrows
JAI, Oxford, United Kingdom
E. Marín, F. Plassard, R. Tomás
CERN, Geneva, Switzerland

As the design of the CLIC Beam Delivery System (BDS) evolves, tuning simulations must be performed on each of the proposed lattice designs to see which system achieves the highest luminosity in the most realistic manner. This work will focus on the tuning simulations performed on the so-called Traditional lattice design for the center-of-mass energy of 3 TeV. The lattice modifications required to target the most important aberrations and the latest tuning results will be presented.

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MOPIK113

Beam Phase Space Tomography for FXR LIA

emittance, space-charge, solenoid, electron

801

Y.H. Wu, Y.-J. Chen
LLNL, Livermore, California, USA

Funding: This work was performed under the auspices of the U.S. Department of Energy by Lawrence Livermore National Laboratory under Contract DE-AC52-07NA27344.
Knowing the initial beam parameters entering an accelerator or a downstream beamline allows us to select transport tunes optimized for a desired accelerator performance. In this study, we report unfolding LLNL's FXR [1] beam parameters by using the tomography technique [2, 3] to construct the beam phase space along the accelerator's downstream beamline. The unfolded phase spaces from tomography and simulations are consistent.

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MOPIK114

End-to-End Energy Variation Study for Induction Radiography Accelerator

target, emittance, beam-transport, solenoid

804

Y.H. Wu, Y.-J. Chen
LLNL, Livermore, California, USA

Funding: This work was performed under the auspices of the U.S. Department of Energy by Lawrence Livermore National Laboratory under Contract DE-AC52-07NA27344.
Energy variation study for beam transport from the entrance of a conceptual induction radiography accelerator to the x-ray target has been reported previously [1]. In this report, we have extended the study upstream to the injector. To achieve minimum emittance growth and to obtain a desired final beam size, we have developed three optimal tunes. Among them, one optimal tune, capable of supressing beam break-up instability and producing acceptable corkscrew motions, is used to study the energy variation effects on radiography performance. The study shows that ±3% energy variation is acceptable.

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MOPIK115

A Design for 10 GeV, High Peak-Current, Tightly Focused Electron Beams at FACET-II

emittance, linac, electron, acceleration

807

G.R. White
SLAC, Menlo Park, California, USA

Funding: This work was sponsored by the Department of Energy under Contract Number: DE-AC02-76SF00515
FACET-II will be a new test facility, starting construction in 2018 within the main SLAC Linac. Its purpose is to build on the decades-long experience developed conducting accelerator R&D at SLAC in the areas of advanced acceleration and coherent radiation techniques with high-energy electron and positron beams. The design consists of a 135-MeV high-brightness photo-injector constructed in an off-axis injection line in Sector 10 of the SLAC Linac, two new 4-bend chicane bunch compressors installed in Sectors 11 and 14, with a third compression stage provided by the existing FACET W Chicane in Sector 20. We develop a design to deliver peak currents more than 160 kA to the Sector 20 interaction region at 10 GeV, with 10 'm-rad emittances at 2 nC bunch charge and 1.4 % rms energy spread. The Sector 20 bunch compressor is re-designed for maximum peak current throughput and minimal emittance degradation via CSR, and the FACET-II compression scheme is optimized. We present 6D start-end beam tracking simulations using Lucretia including ISR, CSR, wakefields and space charge effects.

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MOPIK117

On the Computation of Phase and Energy Gain for a Thin-Lens RF Gap Using a General Field Profile

linac, factory, acceleration, cavity

810

C.K. Allen
ORNL, Oak Ridge, Tennessee, USA

Funding: This material is based upon work supported by the U.S. Department of Energy, Office of Science, Office of Basic Energy Sciences under contract number DE-AC05-00OR22725.
The thin-lens representation for an RF accelerating gap has been well developed and is documented by Lapostolle [5], Weiss [6], Wangler [14], and others [9], [10]. These models assume that the axial electric field is both centered and symmetric so it has a cosine expansion. Presented here is a model that considers general axial fields. Both the cosine and sine transit time factors are required plus their Hilbert transforms. The combination yields a complex Hamiltonian rotating in the complex plane with the synchronous phase. The phase and energy gains are computed in the pre-gap and post-gap regions then aligned with asymptotic values of wave number. Derivations are outlined, examples are shown, and simulations presented.

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MOPIK118

Model Based Optics Studies in the MEBT Section of SNS

emittance, linac, lattice, rfq

814

A.P. Shishlo, A.V. Aleksandrov, A.P. Zhukov
ORNL, Oak Ridge, Tennessee, USA
Y. Liu
KEK/JAEA, Ibaraki-Ken, Japan

Funding: This manuscript has been authored by UT-Battelle, LLC, under Contract No. DE-AC0500OR22725 with the U.S. Department of Energy.
The paper presents the beam dynamics studies for the Medium Energy Beam Transport (MEBT) section of the Spallation Neutron Source (SNS) accelerator. The analysis of measurements is based on the PyORBIT linac model. The diagnostics data includes wire scanners' profiles, slit-harp and slit-slit transverse emittances, MEBT re-bunchers calibration data, and bunch length measurements. The MEBT is a matching section between RFQ and a Drift Tube Linac (DTL). It is also a place for beam halo scraping which helps to reduce beam loss in downstream linac sections. The linac simulation code was benchmarked against the diagnostics data.

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MOPIK123

Beam Dynamics Numerical Studies Regarding CBETA Cornell-BNL ERL

lattice, quadrupole, multipole, optics

824

F. Méot, S.J. Brooks, D. Trbojevic, N. Tsoupas
BNL, Upton, Long Island, New York, USA
S.C. Tygier
UMAN, Manchester, United Kingdom

Funding: Work supported by New York State Energy Research and Development Authority (NYSERDA)
The Cornell-BNL Electron Test Accelerator CBETA is based on a 36 MeV superconducting linac and on a single 4-pass up/4-pass down linear FFAG return loop, for beam acceleration from 6 to 150 MeV and energy recovery. Numerical beam dynamics simulations have accompanied and eventually validated the quadrupole-doublet FFAG cell technology and parameters, and following that the complete return loop, all along the ERL lattice design process. They are key to assessing and validating the ERL optics and beam behavior over the whole acceleration/ER cycle, and in preparing future machine operation. This paper presents various of these beam dynamics studies, including start-to-end simulations.

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MOPVA007

Simulations for Beam-Based Measurements in BERLinPro

cavity, diagnostics, gun, optics

859

M. McAteer, M. Abo-Bakr, J. Knedel, G. Kourkafas, B.C. Kuske, J. Völker
HZB, Berlin, Germany

BERLinPro is an energy recovery linac project whose goal is to establish the accelerator physics knowledge and technology needed to produce 50 MeV beams with high current, low normalized emittance, and low losses. Precise measurements of beam parameters are essential for demonstrating the achievement of performance goals. In this paper we present simulations for measurements of energy, energy spread, and bunch length using the tracking code Astra.

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MOPVA020

S2E Simulation of an ERL-Based High-Power EUV-FEL Source for Lithography

FEL, linac, electron, injection

894

N. Nakamura, R. Kato, T. Miyajima, M. Shimada
KEK, Ibaraki, Japan
R. Hajima
QST, Tokai, Japan
T. Hotei
Sokendai, Ibaraki, Japan

An energy recovery linac(ERL)-based free electron laser(FEL) is a possible candidate of a high-power EUV source for lithography. The ERL can provide a high-current and high-quality electron beam for the high-power FEL and also greatly reduce the dumped beam power and activation compared to ordinary linacs. An ERL-based EUV-FEL source has been designed using available technologies and resources*. For this design, we perform Start-to-End(S2E) simulation from the electron gun to the exit of the decelerating main linac to track the electron beam parameters and to evaluate the FEL performance. The electron bunches from the injector are off-crest accelerated to 800 MeV and compressed in the 1st arc and/or chicane to obtain a high-peak current for high FEL output. After the undulator section for SASE FEL, they are decompressed in the 2nd arc and then decelerated in the main linac to optimize the energy spread or the energy recovery efficiency. This paper will present the S2E simulation for the designed EUV-FEL source.
* N. Nakamura et al., Proc. of ERL2015, Stony Brook, NY, USA, pp.4-9.

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MOPVA025

Step-Like Field Magnets to Uniform Beam Distribution and Experiment at CADS Injector-I

target, dipole, experiment, proton

908

C. Meng, Y. Chen, H. Geng, J.Y. Tang, F. Yan, L. Yu, Y.L. Zhao
IHEP, Beijing, People's Republic of China

High power is the development tendency of proton accelerator, so obtaining uniform beam distribution on target becomes more and more important and critical. The method of using step-like field magnets to obtain a uniform beam distribution on target was presented. In the beamdump line of CADS injector-I test facility four step-like field magnets have been installed to uniform beam distribution to reduce the maximum current density on the beamdump. The magnetic field of step-like field magnets have been measured and discussed in this paper. The simulation results and measurement results of beam uniformization are presented.

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MOPVA039

Manufacturing and Validation Tests of IFMIF Low-Beta HWRs

cavity, cryomodule, SRF, operation

942

G. Devanz, F. Éozénou, L. Maurice, P. Sahuquet, C. Servouin
CEA/DSM/IRFU, France
N. Bazin, P. Carbonnier, P. Charon, G. Disset, P. Hardy, E. Jacques, O. Piquet, D. Roudier
CEA/IRFU, Gif-sur-Yvette, France
J.K. Chambrillon, T. Percerou
CEA/DRF/IRFU, Gif-sur-Yvette, France

The IFMIF accelerator aims to provide an accelerator-based D-Li neutron source to produce high intensity high energy neutron flux to test samples as possible candidate materials to a full lifetime of fusion energy reactors. A prototype of the low energy part of the accelerator is under construction at Rokkasho in Japan. It includes one cryomodule containing 8 half-wave resonators (HWR) operating at 175 MHz .The first manufactured HWR has passed low power tests at 4.2K in vertical cryostat succesfully and exceeds the specifications. It has also been tested in the dedicated horizontal Sathori cryostat equiped with its cold tuning system. The serial production and qualification tests of the 8 cavities which will eventually equip the cryomodule are carried out in parallel. In this paper, we focus on the HWR preparation and test results and give a status of the manufacturing activities.

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MOPVA042

CEA Preliminary Design of the Cryomodules for SARAF Phase II Superconducting Linac

cavity, cryomodule, vacuum, alignment

951

R. Cubizolles, P. Brédy, D. Chirpaz-Cerbat, P. Hardy, F. Leseigneur, C. Madec, J. Plouin
CEA/IRFU, Gif-sur-Yvette, France
N. Bazin
CEA/DSM/IRFU, France
R. Bruce, Th. Plaisant
CEA/DRF/IRFU, Gif-sur-Yvette, France

CEA is committed to deliver a Medium Energy Beam Transfer line and a superconducting linac (SCL) for SARAF accelerator in order to accelerate 5mA beam of either protons from 1.3 MeV to 35 MeV or deuterons from 2.6 MeV to 40.1 MeV. The SCL consists of 4 cryomodules and 4 warm sections with diagnostics at the end of each cryomodule. The first two identical cryomodules host 6 half-wave resonator (HWR) low-beta cavities (β = 0.091), 176 MHz, and 6 focusing superconducting solenoids. The last two identical cryomodule welcome 7 HWR high-beta cavities (β = 0.181), 176 MHz, and 4 solenoids. The paper will presents the preliminary design of the cryomodules.

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MOPVA048

Simulation of the Thermoelectrically Generated Magnetic Field in a SC Nine-Cell Cavity

cavity, SRF, operation, superconducting-RF

968

J.M. Köszegi, J. Knobloch, O. Kugeler
HZB, Berlin, Germany

Several studies showed that thermocurrents generate a magnetic field in a horizontal cavity test assembly or cryomodul, which may get trapped during the supercon-ducting phase transition. The trapped flux causes additional dissipation in the order of 1 to 10 n' during operation and can therefore significantly degrade the quality factor in a TESLA cavity. We simulated the distribution of the generated magnetic field over the whole cavity-tank system for an asymmetric temperature distribution. The asymmetry allows the field to penetrate the RF surface which would be field free in the symmetric case. The calculated results complemented a direct measurement of trapped magnetic flux inside the cavity with a small number of field probes. Finally, the obtained data was combined with RF measurements in three passband modes to determine the overall distribution of trapped magnetic flux due to thermocurrents.

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MOPVA051

Design of the High Power 1.5 GHz Input Couplers for BESSY VSR

coupling, cavity, operation, HOM

978

E. Sharples, M. Dirsat, J. Knobloch, A.V. Vélez
HZB, Berlin, Germany

The Variable pulse length Storage Ring (BESSY VSR) upgrade to BESSY II at Helmholtz-Zentrum Berlin (HZB) requires an upgrade on the RF systems in the form of high-voltage longitudinally focusing super conducting RF cavities of 1.5 GHz ad 1.75 GHz. For operation, coaxial RF power couplers capable of handling 13 kW peak power at standing wave operation are required for both the 1.5 GHz and 1.75 GHz cavities. The coupler is based on a design by Cornell University with modifications to suit frequency and coupling requirements. The coupler is intended to provide variable coupling with a range of Qext from 6x10⁶ to 6x10⁷ to allow flexibility to adjust to operating conditions of BESSY VSR. Here we present the RF design of the high-power coaxial coupler for BESSY VSR along with the design of the test stand for conditioning a pair of couplers.

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MOPVA054

High Power RF Coupler for the CW-Linac Demonstrator at GSI

cavity, Windows, linac, ion

990

M. Heilmann, W.A. Barth, S. Yaramyshev
GSI, Darmstadt, Germany
M. Amberg, M. Basten, R. Blank, M. Busch, F.D. Dziuba, H. Podlech, M. Schwarz
IAP, Frankfurt am Main, Germany
K. Aulenbacher
IKP, Mainz, Germany
K. Aulenbacher, W.A. Barth, V. Gettmann, M. Miski-Oglu
HIM, Mainz, Germany
W.A. Barth, S. Yaramyshev
MEPhI, Moscow, Russia

The planned super-heavy element (SHE) research project investigates heavy ions near the coulomb barrier in future experiments. A superconducting (sc) continuous wave (cw) CH-Linac Demonstrator was developed and installed behind the High Charge State Injector (HLI) at GSI Darmstadt, Germany. In future the advanced cw-LINAC setup, with several CH-cavities, will accelerates the heavy ion beam from HLI with an energy of 1.4 MeV/u up to 3.5 - 7.3 MeV/u. The RF power of several kW will be coupled capacitively into the CH-cavities with minimal reflection at an operation frequency of 217 MHz. Two ceramic windows (Al2O3) are installed inside the RF coupler, to reduce the premature contamination of the cavity and as an additional vacuum barrier. The CH-cavity will be operated at cryogenic temperature (4 K) and will be increased to room temperature along the RF coupler. The optimally adapted RF coupler design, providing minimal RF losses and simultaneously maximal performance, was optimized by electromagnetic simulations. An RF coupler design with a reflection-free RF adaptor as well as the temperature distribution along the coupler will be presented.

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MOPVA064

Multipacting Study in INFN-LASA ESS Medium-Beta Cavity

cavity, SRF, site, electron

1019

J.F. Chen, M. Bertucci, A. Bosotti, P. Michelato, L. Monaco, C. Pagani, R. Paparella, D. Sertore
INFN/LASA, Segrate (MI), Italy
S. Pirani
ESS, Lund, Sweden

We present Multipacting studies in ESS Medium-Beta cavities of INFN-LASA design with both simulation and experimental results. The simulation on the ideal cavity shape with both FishPact and MultiPac2.1 codes shows that multipacting appears in a very small region near equator where the weld seam exists. A simulation with more realistic cavity shape considering the weld seam at cell equators has also been done out showing similar results for end cell but a remarkable mitigation for inner cell. During the vertical tests at LASA, Multipacting is frequently observed but with no limitation to the cavity performance, which well confirms the MP predicted by the simulations.

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MOPVA087

Low Betta Superconducting Cavity for the New Injector Linac for Nuclotron-NICA

cavity, linac, multipactoring, accelerating-gradient

1058

M. Gusarova, T.A. Bakhareva, M.V. Lalayan, S.V. Matsievskiy, N.P. Sobenin, D.V. Surkov, K.V. Taletskiy, V. Zvyagintsev
MEPhI, Moscow, Russia
A.A. Bakinowskaya, V.S. Petrakovsky, A.I. Pokrovsky, D.A. Shparla
Physical-Technical Institute of the National Academy of Sciences of Belarus, Minsk, Belarus
A.V. Butenko, G.V. Trubnikov
JINR/VBLHEP, Dubna, Moscow region, Russia
V. Zvyagintsev
TRIUMF, Vancouver, Canada

The results of the RF, mechanical and multipactor discharge simulations of the 162 MHz quarter wave resonator (QWR) for New Superconducting Injector Linac for Nuclotron-NICA are presented. Cavity design in conjunction with manufacturing features is discussed.

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MOPVA088

Medium Betta Superconducting Cavity for the New Injector Linac for Nuclotron-NICA

cavity, linac, multipactoring, accelerating-gradient

1061

M. Gusarova, M.V. Lalayan, N.P. Sobenin, D.V. Surkov, K.V. Taletskiy
MEPhI, Moscow, Russia
A.A. Bakinowskaya, V.S. Petrakovsky, A.I. Pokrovsky, D.A. Shparla
Physical-Technical Institute of the National Academy of Sciences of Belarus, Minsk, Belarus
A.V. Butenko, G.V. Trubnikov
JINR/VBLHEP, Dubna, Moscow region, Russia

The results of the electrodynamical and multipactor discharge simulations of the medium betta superconducting cavity for New Superconducting Injector Linac for Nuclotron-NICA are presented. Different designs of CH and Spoke cavities are compared and the optimal one is chosen.

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MOPVA091

Investigation of HOM Frequency Shifts Induced by Mechanical Tolerances

cavity, HOM, operation, cryogenics

1071

S. Pirani, M. Eshraqi, M. Lindroos
ESS, Lund, Sweden
A. Bosotti, J.F. Chen, P. Michelato, C. Pagani, R. Paparella, D. Sertore
INFN/LASA, Segrate (MI), Italy
T.P.Å. Åkesson
Lund University, Department of Physics, Lund, Sweden

We present Higher Order Mode (HOM) studies on ESS Medium-Beta cavity of INFN-LASA design, including both simulation and measurement results. Mechanical tolerances of the fabrication process might shift HOMs frequencies toward harmonics of the bunch frequency. Both simulation and measurements at room and cryogenic temperature show that INFN LASA cavity is fully compatible with ESS requirements.

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MOPVA097

Finite Element Analysis on Helium Discharge from Superconducting RF in the Storage Ring Tunnel

cryogenics, SRF, cavity, distributed

1085

J.-C. Chang, F. Z. Hsiao, J.C. Huang, S.P. Kao, H.C. Li, W.R. Liao, C.Y. Liu, H.H. Tsai, Z.-D. Tsai
NSRRC, Hsinchu, Taiwan

Liquid helium for transferring cooling power from the cryogenic plant to the magnets and SRF cavities had been widely applied on the advanced large superconducting particle accelerators. For requirements of high stable and reliable operation, many efforts have been put into the improvement and modification of the cryogenic system. However, personnel safety is another critical issue of the cryogenic system. Once large liquid helium was released on the atmospheric tunnel, the volume of helium will expand several hundred times and cause oxygen deficiency in short time due to sudden change of helium density. In this study, we applied numerical simulation to analyze helium discharge through a SRF cavity in the TPS tunnel.

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MOPVA100

Atomic Layer Deposition of Niobium Nitride from Different Precursors

plasma, niobium, experiment, controls

1094

P. Pizzol, P. Chalker, J.W. Roberts, J. Wrench
The University of Liverpool, Liverpool, United Kingdom
O.B. Malyshev, R. Valizadeh
STFC/DL/ASTeC, Daresbury, Warrington, Cheshire, United Kingdom

Advancements in technology have taken bulk niobium cavities close to their theoretical operational limits of 45 MV/m, pushing the research to explore novel materials, such as niobium based alloys . Theoretical studies suggest that a composite material composed of alternative superconductor / insulator multilayers would surpass the bulk niobium limits. Chemical vapour deposition (CVD) can deposit mi-crons thick Nb films in less than an hour, at the expense of precise thickness control. Atomic layer deposition (ALD), instead, even if considerably slower than CVD can be used in applications where the thickness of the deposited layers needs to be controlled with a resolution down to the nanometer. This article presents the preliminary results obtained by using plasma assisted ALD techniques to deposit NbN based compounds starting from chlorinated precursors and organic ones, and the design for a new deposition system currently being built at the Daresbury Laboratories.

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MOPVA102

Modeling the Low Level RF Response on the Beam during Crab Cavity Quench

cavity, luminosity, SRF, klystron

1098

R. Apsimon, G. Burt, A.C. Dexter
Cockcroft Institute, Lancaster University, Lancaster, United Kingdom
R.B. Appleby
UMAN, Manchester, United Kingdom
P. Baudrenghien, K.N. Sjobak
CERN, Geneva, Switzerland

The High Luminosity Upgrade for the LHC (HL-LHC) relies on crab cavities to compensate for the luminosity reduction due to the crossing angle of the colliding bunches at the interaction points. In this paper we present the simulation studies of cavity quenches and the impact on the beam. The cavity voltage and phase during the quench is determined from a simulation in Matlab and used to determine the impact on the beam from tracking simulations in SixTrack. The results of this study are important for determining the required machine protection and interlock systems for HL-LHC.

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MOPVA117

Performance of a SRF Half-Wave-Resonator Tested at Cornell for the RAON Project

cavity, radiation, SRF, pick-up

1123

M. Ge, F. Furuta, T. Gruber, D.L. Hall, S.W. Hartman, C. Henderson, M. Liepe, S. Lok, T.I. O'Connell, P.J. Pamel, J. Sears, V. Veshcherevich
Cornell University (CLASSE), Cornell Laboratory for Accelerator-Based Sciences and Education, Ithaca, New York, USA
B.H. Choi, J. Joo, J.W. Kim, W.K. Kim, J. Lee, I. Shin
IBS, Daejeon, Republic of Korea

A prototype half-wave-resonator (HWR) with frequency 162.5MHz and geometrical \beta=0.12 for the RAON project is currently undergoing testing at Cornell University. Detailed vertical performance testing includes (1) test of the bare cavity without the helium tank; (2) test of the dressed cavity with helium tank. In this paper, we report on the development of the test infrastructure, test results, and performance data analysis.

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MOPVA119

Surface Analysis of Features Seen on Nb3Sn Sample Coupons Grown by Vapour Diffusion

niobium, SRF, cavity, site

1130

D.L. Hall, M. Liepe, J.T. Maniscalco, R.D. Porter
Cornell University (CLASSE), Cornell Laboratory for Accelerator-Based Sciences and Education, Ithaca, New York, USA
T. Arias, P. Cueva, D.A. Muller, N. Sitaraman
Cornell University, Ithaca, New York, USA

As a high-kappa superconductor with a coherence length of 7 nm, the superconductor Nb3Sn is highly susceptible to material features at the sub-micron scale. For niobium surfaces coated with a thin layer of Nb3Sn using the vapour diffusion method, the polycrystalline nature of the film grown lends to the possibility that performance-degrading non-uniformities may develop. In particular, regions of insufficiently thick coating and tin-depletion have been seen to occur in sample coupons. In the interests of understanding how to control the presence and nature of such features, it is necessary to know how they form. In this paper we stop the coating at defined instances to gain a stop-motion image of the growth of the layer, and use SEM and TEM techniques to image the development of the features seen in previously coated samples. We demonstrate that surface pre-anodisation can suppress the formation of thin film regions, and apply this technique to a single-cell cavity. Contemporarily, we use TEM with EDS mapping to monitor grain boundaries and tin-depleted regions within the layer.

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MOPVA121

Frequency Tuner Development at Cornell for the RAON Half-Wave-Resonator

cavity, cryomodule, cryogenics, controls

1134

M. Ge, F. Furuta, T. Gruber, D.L. Hall, S.W. Hartman, C. Henderson, M. Liepe, S. Lok, T.I. O'Connell, P.J. Pamel, P. Quigley, J. Sears, V. Veshcherevich
Cornell University (CLASSE), Cornell Laboratory for Accelerator-Based Sciences and Education, Ithaca, New York, USA
B.H. Choi, J. Joo, J.W. Kim, W.K. Kim, J. Lee, I. Shin
IBS, Daejeon, Republic of Korea

The half-wave-resonators (HWR) for the RAON pro-ject require a slow frequency tuner that can provide at least 80 kHz tuning range. Cornell University is currently in the process of designing, prototyping, and testing this HWR tuner. In this paper, we present the tuner design, prototype fabrication, and first test results.

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MOPVA130

Development of Waveguide HOM Loads for BERLinPro and BESSY-VSR SRF Cavities

HOM, cavity, SRF, network

1160

J. Guo, F. Fors, J. Henry, R.A. Rimmer, H. Wang
JLab, Newport News, Virginia, USA
H.-W. Glock, A. Neumann, A.V. Tsakanian, A.V. Vélez
HZB, Berlin, Germany

Two ongoing accelerator projects at Helmholtz-Zentrum Berlin (HZB), BERLinPro and BESSY-VSR, need to design three different SRF cavities, a 1.3GHz cavity in BERLinPro and 1.5GHz/1.75GHz cavities in BESSY-VSR. These cavities have adopted waveguide HOM dampers in their design, with a few tens of watts HOM power in each load for BERLinPro and a few hundred watts for BESSY-VSR. JLab is collaborating with HZB prototyping these HOM loads. In this paper, we will report on the integrated RF-thermal-mechanical design of the loads, as well as the fabrication and testing results.

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MOPVA132

Production of Copper-Plated Beamline Bellows and Spools for LCLS-II

cryomodule, controls, cavity, vacuum

1167

K.M. Wilson, B. Carpenter, E. Daly, N.A. Huque, T. Peshehonoff
JLab, Newport News, Virginia, USA
T.T. Arkan, A. Lunin, K.S. Premo
Fermilab, Batavia, Illinois, USA

Funding: This work was supported by the LCLS-II Project and the U.S. Department of Energy, Contract DE-AC02-76SF00515
The SLAC National Accelerator Laboratory is currently constructing a major upgrade to its accelerator, the Linac Coherent Light Source II (LCLS-II). Several Department of Energy national laboratories, including the Thomas Jefferson National Accelerator Facility (JLab) and Fermi National Accelerator Laboratory (FNAL), are participating in this project. The 1.3-GHz cryomodules for this project consist of eight cavities separated by bellows (expansion joints) and spools (tube sections), which are copper plated for RF conduction. JLab is responsible for procurement of these bellows and spools, which are delivered to JLab and FNAL for assembly into cryomodules. Achieving accelerator-grade copper plating is always a challenge and requires careful specification of requirements and application of quality control processes. Due to the demanding technical requirements of this part, JLab implemented procurement strategies to make the process more efficient as well as provide process redundancy. This paper discusses the manufacturing challenges that were encountered and resolved, as well as the strategies that were employed to minimize the impact of any technical issues.

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MOPVA141

Input RF Coupler Design for Energy Compensator Cavity in eRHIC

cavity, radiation, impedance, synchrotron

1184

C. Xu, S. Bellavia, I. Ben-Zvi, M. Blaskiewicz, Y. Hao, K.S. Smith, R. Than, A. Zaltsman
BNL, Upton, Long Island, New York, USA

Funding: Work supported by Brookhaven Science Associates, LLC under Contract No. DE-AC02-98CH10886 with the U.S. Department of Energy.
This report gives a detail design of a 1.3 GHz input coupler for second harmonic cavity for eRHIC project. This coupler is designed to transmit 200KW CW RF to the cavity to compensate the synchrotron radiation loss. This report include RF and thermal simulation for this design.

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MOPVA143

Trim Tuning of SPS-Series DQW Crab Cavity Prototypes

cavity, target, operation, controls

1187

S. Verdú-Andrés, J. Skaritka, Q. Wu
BNL, Upton, Long Island, New York, USA
S. Baurac, C.H. Boulware, T.L. Grimm, J.A. Yancey
Niowave, Inc., Lansing, Michigan, USA
W.A. Clemens, E.A. McEwen, H. Park
JLab, Newport News, Virginia, USA
H. Park
ODU, Norfolk, Virginia, USA
A. Ratti
LBNL, Berkeley, California, USA
A. Ratti
SLAC, Menlo Park, California, USA

Funding: Work partially supported by US DOE via BSA LLC contract No.DE-AC02-98CH10886 and by the US LARP program.
The final steps in the manufacturing of a superconducting RF cavity involve careful tuning before the final welds to match the target frequency as fabrication tolerances may introduce some frequency deviations. The target frequency is chosen based on analysis of the shifts induced by remaining processing steps including acid etching and cool down. The baseline fabrication of a DQW crab cavity for the High Luminosity LHC (HL-LHC) envisages a first tuning before the cavity subassemblies are welded together. To produce a very accurate final result, subassemblies are trimmed to frequency in the last machining steps, using a clamped cavity assembly for RF measurements. This paper will describe the trim tuning of one of the SPS prototype DQW crab cavities fabricated by Niowave.

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TUOBA3

Strain and Temperature Measurements From the SNS Mercury Target Vessel During High Intensity Beam Pulses

target, radiation, data-acquisition, injection

1230

W. Blokland, Y. Liu, B.W. Riemer, M. Wendel, D.E. Winder
ORNL, Oak Ridge, Tennessee, USA

Funding: ORNL is managed by UT-Battelle, LLC, under contract DE-AC05-00OR22725 for the U.S. Department of Energy. This research was supported by the DOE Office of Science, Basic Energy Science, Scientific User Facilities.
To better understand the mechanical impact of the proton beam on the lifetime on Spallation Neutron Source (SNS*) mercury-filled, stainless steel targets, these targets are now instrumented with optical and metal strain sensors, temperature sensors, and accelerometers. The strain and temperature sensors are placed inside the target vessel, between the water shroud and mercury vessel, while the accelerators are placed outside on the target mount and on the mercury return line. We now have data from four targets. The first instrumented target used regular multimode optical sensors, while later targets have used radhard multimode sensors. We are also developing super-radhard single-mode optical strain sensors to get data further into the production cycle. In this paper, we describe the data-acquisition system, compare the measured strain to the simulated strain for the different targets, estimate the survivable radiation level for each type of sensor, and discuss the implications of the results on the lifetime of the target.

Slides TUOBA3 [37.266 MB]

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TUOAB2

First Observation of the LHC Beam Halo Using a Synchrotron Radiation Coronagraph

background, synchrotron, radiation, photon

1244

T.M. Mitsuhashi
KEK, Ibaraki, Japan
E. Bravin, F. Roncarolo, G. Trad
CERN, Geneva, Switzerland

A test coronagraph for the observation of beam halo has been installed in the Synchrotron radiation monitor line LHCB2 in 2015. This coronagraph is commissioned with LHC operation at 450GeV (injection energy). After some optical testing of the coronagraph with visible Synchrotron radiation in B2, we try to observe artificially-made beam halo. The beam halo of 10^-3 order of magnitude against the beam core is excited by the kicker of the transverse damper. We have succeeded to observe a diffraction noise free image of beam halo. The effect of beam collimator is also observed. Reduction of beam halo intensity was found nicely proportional to the simultaneously-recorded beam loss.

Slides TUOAB2 [8.302 MB]

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TUPAB001

Proof of Concept of CLIC Final Focus Quadrupoles Stabilization

controls, quadrupole, collider, ground-motion

1290

G. Balik, B. Aimard, L. Brunetti
IN2P3-LAPP, Annecy-le-Vieux, France
B. Caron
SYMME, Annecy-le-Vieux, France

The Compact LInear Collider (CLIC) [1] luminosity requires extremely low beam emittances. Therefore, high beam position stability is needed to provide cen-tral collisions of the opposing bunches. Since ground motion (GM) amplitudes are likely to be larger than the required tolerances, an Active Vibration Control (AVC) system is required to damp quadrupole motion to the desired value of 0.2 nm RMS at 4 Hz. This paper focuses on the vertical final focus quadrupoles (QD0, QF1) stabilization and demonstrates its feasibility. An AVC system to be installed under QD0 and QF1 has been developed and successfully tested at LAPP. Based on a dedicated homemade sensor with an ex-tremely low internal noise level of 0.05 nm at 4 Hz, it damps GM in the frequency range [3;70] Hz by up to 30 dB, leading to RMS values of approximately 0.25 nm at 4 Hz. Simulations based on GM measured in the Compact Muon Solenoid (CMS) experimental hall [2] show that with such a GM level, the specifications would only be achieved with a Passive Insulation (PI) system, which would filter ground motion starting at ~ 25 Hz

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TUPAB005

Investigation of Beam Variation and Emittance Growth Simulation With Both Misalignments and the Beam Jitter for SuperKEKB Injector Linac

emittance, linac, electron, quadrupole

1304

Y. Seimiya, K. Furukawa, T. Higo, F. Miyahara, M. Satoh, T. Suwada
KEK, Ibaraki, Japan

Funding: This work was supported by JSPS KAKENHI Grant Number 16K17545.
The SuperKEKB is e⁺/e⁻ circular collider for high luminosity, 8Â¥times10³⁵ as a target value. For the high luminosity, the injector linac is required to transport low emittance high-charged electron beam and positron beam to the ring. A charged beam with an offset from a center of cavity is affected by the wakefield depending on both the offset size in the cavity and longitudinal particle position in the beam. The wakefield causes emittance growth. This growth can be suppressed by appropriate orbit control so as to cancel the wakefield effect of the cavities in total. On the other hands, the beam variation in 6-dimensional phase space also induces the emittance growth. Emittance growth by both misalignments and 6-dimensional beam jitter was evaluated by particle tracking simulation. Investigation of beam jitter and drift was also performed by correlation analysis between beam position and measured parameter, charge or temperature.

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TUPAB011

Beam Dynamics Simulation in Two Versions of New Photogun for FCC-ee Electron Injector Linac

linac, injection, electron, beam-loading

1326

S.M. Polozov, T.V. Bondarenko
MEPhI, Moscow, Russia

New high-energy frontier project FCC is now under development at CERN. The project includes three modes: ee, hh and eh interactions for FCC. New injection system for FCC-ee is planned to consist of new ~ 2-14 GeV electron linac and electron-positron converter. Injector linac should provide two regimes: ~250 pC bunches for injection and ~6 nC bunches for e⁻/e⁺ conversion. Two possible schemes of photogun are comprised and results of beam dynamics simulation in both FCC-ee injection linac photoguns are discussed.

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TUPAB012

Comparison of Prismatic and Circular Biperiodical Accelerating Structures of 27 GHz Operating Frequency

coupling, linac, impedance, alignment

1330

Yu.D. Kliuchevskaia, S.M. Polozov
MEPhI, Moscow, Russia

As known a biperiodical accelerating structure (BAS) represents as a system based on disk loaded waveguide (DLW) operating on Pi/2 mode and is widely used for the compact electron linacs. Earlier such structure with operating frequency of 27 GHz was proposed for medical application and beam dynamics simulations and electrodynamics modeling were done [1-2]. It was shown that such structure manufacturing should have very high accuracy and can be manufactured using electro erosive technology only. It is very complex for axi-symmetrical geometry to use such technology. Interesting option will to use a prismatic geometry BAS. In this report the design of a prismatic and disk-loaded BAS will discus, simulation results and analysis will presented.

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TUPAB013

Beam Dynamics Study and Electrodynamics Simulations for the CW RFQ

rfq, cavity, linac, Windows

1333

S.M. Polozov, W.A. Barth, T. Kulevoy, Y. Lozeev, S. Yaramyshev
MEPhI, Moscow, Russia
W.A. Barth, S. Yaramyshev
GSI, Darmstadt, Germany
W.A. Barth
HIM, Mainz, Germany
T. Kulevoy, S.M. Polozov
ITEP, Moscow, Russia

A compact university scale CW research proton accelerator, as well as driver linac with three branches of experimental beam lines, delivering beam energy of 3, 30 and 100 MeV for experiments, are recently under development in Russia. First results of the beam dynamics simulations for such a linac were already shown in *. The recently developed advanced RFQ cavity design is presented. The low energy beam transport line (LEBT), dedicated to transport proton beam from an ECR ion source, as well as to match beam emittance to the RFQ acceptance, was investigated. The results of beam dynamics simulations for LEBT are discussed.
* W.Barth, T.Kulevoy, S.Polozov, S.Yaramyshev, Proc. of HB-2016, 188-190.

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TUPAB021

The Study of Focus-Dependent Dark Current for AREAL RF Photogun

electron, gun, solenoid, experiment

1358

L. Hakobyan, H. Davtyan, B. Grigoryan, A. Vardanyan
CANDLE SRI, Yerevan, Armenia

AREAL (Advanced Research Electron Accelerator Laboratory) is a project of linear accelerator based facility aimed to produce ultra-short electron bunches with small emittance. In the first phase of AREAL project an electron beam with energy up to 5 MeV is produced by the electron RF photogun and used for irradiation experiments in biology, microelectronics and accelerator technology development. For such experiments the exact calculation of absorbed dose and electron bunch peak current is one of important conditions. The presence of a dark current in electron gun affects the electron emission from photocathode, the exact absorbed dose calculation, and in general harms the machine performance. In this paper the estimation of dark current amount, produced in the electron gun, the ways to avoid its influence on experiments are discussed. The dark current measurements are compared with the simulation results. The electron beam separation from a dark current is discussed.

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TUPAB043

Design and Simulation of Voltage Multiplier Column of a 300keV, 10mAParallel Fed Cockcroft Walton Electron Accelerator for Industrial Applications

electron, coupling, software, gun

1421

M. Nazari, F. Abbasi Davani, F. Ghasemi
Shahid Beheshti University, Tehran, Iran
S. Ahmadiannamin
ILSF, Tehran, Iran

In this article a 300keV, 10mA multiplier column has been designed for a parallel fed Cockcroft Walton electron accelerator for industrial applications. The parallel fed Cockcroft Walton multiplier is a capacitive coupling multiplier with diode rectification which can convert an input RF voltage to a low ripple output DC voltage. In this research tried to get a low ripple (300keV output) dc voltage. At first, the voltage multiplier column has been simulated with pspice simulation software. After doing the pspice simulations, optimum value of different parameters has been get. At the end we try to get the optimum values of pspice simulations with a mechanical design with CST STODIO. The mechanical design of voltage multiplier and its equivalent circuit hah a good accordance with each other.

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TUPAB044

SIMULATION, MEASUREMENT AND TUNING OF A PROTOTYPE DISK LOADED RF CAVITY

electron, cavity, linac, operation

1424

S. Ahmadiannamin
ILSF, Tehran, Iran
F. Abbasi, F. Ghasemi
Shahid Beheshti University, Tehran, Iran
M. Lamehi, M. Shirshekan
IPM, Tehran, Iran

Constant impedance accelerator RF cavities are constructed from similar resonator cells that stacked to each other. Best operation condition is achieved when all of cells resonate in one resonance frequency with similar quality factors. So, measurement and tuning of RF cavities is the critical step for final best operation of linear accelerators. In this paper, the electromagnetic computer simulations, RF measurement and final tuning of a nine cell periodic accelerator structure was represented. All of cavities tuned in one resonant frequency and according to theoretical concepts we obtain nine resonant modes from RF measurements by vector network analyzer.

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TUPAB045

Design and Construction of a Pre-Buncher for Iranian Low Energy Linear Accelerator

cavity, electron, linac, coupling

1428

S. Ahmadiannamin
ILSF, Tehran, Iran
M. Bahrami, M.R. Khalvati, M. Lamehi, H. Shaker, M. Shirshekan
IPM, Tehran, Iran

Iranian IPM low energy linear accelerator project (e-Linac) is in its final steps for commissioning. Beam dynamic simulations with and without Pre-buncher prior to buncher was done. The results represent improvement in capturing efficiency better than 25% by application of Pre-buncher cavity. In this paper, we present the simulation, construction, RF measurements and vacuum test results. After construction, we measured RF reflection coefficient better than -33 dB in the nominal frequency of 2997.9 MHz with quality factor of 4500.

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TUPAB047

Design of a Low Emittance High Current Photocathode RF Gun for the IPM Linear Accelerator

cavity, gun, emittance, focusing

1431

M. Dayyani Kelisani, H. Shaker
CERN, Geneva, Switzerland
H. Shaker
IPM, Tehran, Iran

The IPM accelerator project is developing a 50 MeV linear accelerator as an injector for a terahertz source or an IR FEL. The design specifications require a laser driven photocathode located in one end of a high gradient RF cavity operated at 3 GHz frequency and a solenoid channel for the beam transport. In this work, we report on the RF design of an special photocathode RF gun and its associated focusing channel for the emittance compensation process along the whole injector.

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TUPAB070

S-Band Accelerating Structure for High-Gradient Upgrade of TTX

electron, impedance, accelerating-gradient, linac

1485

D.Z. Cao, H.B. Chen, Y.-C. Du, W. Gai, W.-H. Huang, X.C. Meng, J. Shi, C.-X. Tang, X.W. Wu, H. Zha
TUB, Beijing, People's Republic of China

Thomson scattering x-ray source is an indispensable scientific X-ray imaging tool in various research fields. The 3-meter S-band linac in Tsinghua Thomson scatter-ing X-ray source (TTX) has been running at an accelerat-ing gradient of 15 MV/m so far. The gradient will be upgraded to 30MV/m by replacing the old structure with a shorter linac. Detailed optimization of the RF design of the new S-band linac structure is presented in this paper. Finally, further research on energy upgrade with X-band structures are also discussed.

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TUPAB086

Design Study of a High-Intensity, Low-Energy Electron Gun

gun, electron, emittance, FEL

1517

Q. Zhang, K. Fan, T. Hu, K.F. Liu, Z.Y. Mei
HUST, Wuhan, People's Republic of China

An independently-tunable-cells thermionic RF gun (ITC-RF gun) is adopted in a compact FEL-THz facility due to its compactness, low-cost and high intensity. An electron gun is required to generate maximum beam current of 3.2 A at low energy of 15keV for the ITC-RF gun, which creates difficulties for the design of electron gun because of the strong space charge effect. A double-anode gridded gun structure is adopted that controls the beam current easily while maintains the energy dispersion less than 0.5%, with high perveance and high compression ratio. CST code has been used extensively for design optimization, which includes electrode shape, influences of grid, installation errors. A measurement scheme is also proposed for key parameters verification. Beam current, emittance and energy dispersion can be measured.

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TUPAB117

Conceptual Design of a Novel SCAPE Undulator

undulator, photon, lattice, vacuum

1596

Y. Ivanyushenkov, J.F. Fuerst, E. Gluskin, Q.B. Hasse, M. Kasa, Y. Shiroyanagi, E. Trakhtenberg
ANL, Argonne, Illinois, USA

Funding: Work supported by the U.S. Department of Energy, Office of Science, under Contract No. DE-AC02-06CH11357.
A concept of a novel SuperConducting Arbitrarily Polarizing Emitter, or SCAPE, has recently been suggested at the Advanced Photon Source. It consists of two pairs - both vertical and horizontal - of superconducting planar magnets assembled around a beam vacuum chamber. Such a device will be capable of generating either planar or circularly polarized photons, depending on which pair of magnets is energized. The magnetic simulation suggests that due to the employment of superconducting technology, the expected magnetic field is higher than that of the APPLE undulators. The SCAPE undulators could be useful for the fourth generation of storage rings with a multi-bend achromat lattice, as well as for the FELs where utilization of round beam vacuum chambers becomes possible. The results of magnetic modelling, as well as the design concept of the SCAPE, are presented.

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TUPAB122

Engineering Optimization of The Support Structure and Drive System for the LCLS-II Soft X-Ray Undulator Segments

undulator, photon, experiment, laser

1602

A.J. DeMello, D. Arbelaez, D. Bianculli, A.P. Brown, J.N. Corlett, J.R. Dougherty, D.E. Humphries, J.-Y. Jung, M. Leitner, S. Marks, K.A. McCombs, K.L. Ray, D.A. Sadlier, D. Schlueter, E.J. Wallén
LBNL, Berkeley, California, USA

Funding: Work supported by the Director, O'ce of Science, of the U.S. Department of Energy under Contract No. DE-AC02-05CH11231.
The Linear Coherent Light Source II (LCLS-II) project, an upgrade to the free-electron laser facility at SLAC, is replacing the undulator system from a fixed gap to a variable gap system to enable tuning of the photon energy range. The LCLS-II project will include a soft x-ray (SXR) beam line and a hard x-ray (HXR) beam line. The SXR undulators are conventional vertical-gap horizontally-polarizing devices while the HXR undulators are novel horizontal-gap vertically-polarizing devices. This paper describes in detail the development of the SXR mechanical support structure and drive system. The effort has included extensive analysis of the various components to ensure that the undulators will perform within the design specifications. Engineering simulations undertaken and experiments performed to validate the computer modeling are presented together with measurement results from prototype and pre-production undulators.

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TUPAB124

Development of the Manufacturing and QA Processes for the Magnetic Modules of the LCLS-II Soft X-Ray Undulators

undulator, status, laser, free-electron-laser

1609

K.L. Ray, D. Arbelaez, A.J. Band, D. Bianculli, A.P. Brown, J.N. Corlett, A.J. DeMello, J.R. Dougherty, L. Garcia Fajardo, K. Hanzel, D.E. Humphries, J.-Y. Jung, D. Leitner, M. Leitner, S. Marks, K.A. McCombs, D.V. Munson, D.A. Sadlier, D. Schlueter, E.J. Wallén, V. Waring, A. Zikmund
LBNL, Berkeley, California, USA
D.E. Bruch, A.L. Callen, G. Janša, D.S. Martinez-Galarce, H.-D. Nuhn, E. Ortiz, Â. Oven, M. Rowen, Z.R. Wolf
SLAC, Menlo Park, California, USA

Funding: Work supported by the Director, Office of Science, of the U.S. Department of Energy under Contract No. DE-AC02-05CH11231.
A new free electron laser being built at SLAC National Accelerator Laboratory, the Linear Coherent Light Source II (LCLS-II), will use 21 soft x-ray undulators (SXR) and 32 hard x-ray undulators (HGVPU). Lawrence Berkeley National Laboratory (LBNL) is responsible for the design and manufacturing of all variable-gap, hybrid permanent-magnet undulators. The physics requirements for the undulators specify a longitudinal pole misalignment maximum rms error of 25 μm and a vertical pole misalignment maximum error of 50 μm. In addition, magnet positioning critically influences the gap-dependent field properties due to saturation effects at the smallest operational gaps. This paper discusses the manufacturing and QA methods developed to carefully control the longitudinal and vertical pole and magnet positions during undulator production. Inspection results are discussed based on data gathered during construction of a prototype as well as pre-production soft x-ray undulator.

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TUPAB133

Perturbation Analysis for Beam Trajectories. Determining Local Shielding Containment for LCLS-II

shielding, quadrupole, dipole, undulator

1637

M. Santana-Leitner
SLAC, Menlo Park, California, USA

Funding: Work supported by U.S. Department of Energy contract DE-AC02-76SF00515
Containment of beam losses by halo and momentum/energy collimators is a well-established practice for normal operation of particle accelerators where tracking codes are applied. However, for exceptional events, such as magnet power failures, severe lattice mis-match, etc., ad-hoc analytical approaches are typically applied. Oftentimes those simplified methods are not automatic; they don't define the full phase-space of mis-steered trajectories and cannot keep up with beam-line upgrades. Moreover, there may exist a disconnect between the teams analyzing consequences of errant beams and those involved in beam-line design. With electron beams exceeding 100 kW, design of LCLS-II at SLAC National Accelerator Laboratory required exhaustive beam-containment studies to avoid potential destruction of components and excessive dose rates. The geometry of the different beam-lines and the nominal optics was built with MadFLUKA [1], and FLUKA [2] Monte Carlo code along with perturbations to magnetic fields was used to inspect failures compatible with beam operations and hardware settings. Consequences of mis-steered rays and the respective mitigations were directly analyzed with FLUKA.
[1] M. Santana-Leitner et al., MadFLUKA Beam Line 3D Builder. Simulation of Beam Loss Propagation in Accelerators, IPAC14 proceedings, MOPME040
[2] A. Ferrari et al, The FLUKA Code: Developments and Challenges for High Energy and Medical Applications, Nuclear Data Sheets 120, 211-214 (2014)

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TUPAB137

Evaluation of FEL Performance with a Longer Injector Drive Laser Pulse at the LCLS

laser, emittance, FEL, electron

1651

F. Zhou, Y. Ding, J.P. Duris, S. Gilevich, P. Hering, S. Vetter
SLAC, Menlo Park, California, USA

Funding: US DOE under grant No. DE-AC02-76SF00515.
It is known that the X-ray Free Electron Laser (FEL) performance strongly depends on the beam emittance and peak current. Lengthening injector laser pulse can improve the injector emittance but the injector peak current is notably compromised, in comparison to nominal laser pulse. With this longer laser pulse, a stronger bunch compression through downstream bunch compressors is thus required to keep same final peak current as the nominal laser pulse mode. This process may cause stronger micro-bunching effect. At the LCLS, we perform preliminary experiments with doubling injector laser pulse. In this paper, we present the experimental results of the injector emittance, microbunching effects and FEL performance with the longer drive laser pulse.

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TUPAB147

The Final RF-Design of the 36 MHz-HSI-RFQ-Upgrade at GSI

rfq, multipole, alignment, resonance

1678

M. Baschke, H. Podlech
IAP, Frankfurt am Main, Germany
L. Groening, S. Mickat, C. Zhang
GSI, Darmstadt, Germany

In Darmstadt/Germany the existing accelerator cite GSI is expanding to one of the biggest joint research projects worldwide: FAIR, a new antiproton and ion research facility with so far unmatched intensities and quality. The existing accelerators will be used as pre-accelerators and therefor need to be upgraded to fulfill the requirements with respect for intensity and beam quality. In a first step the 9.2 m long 36 MHz-HSI-RFQ for high current beams will obtain new electrodes to reach the specific frequency and to allow a higher electric strength. Therefor several simulations with CST MWS have been done. The final RF-design will be presented.

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TUPAB148

Investigation of a Splitring-RFQ for High Current Ion Beams at Low Frequencies

rfq, resonance, impedance, ion

1680

M. Baschke, H. Podlech, A. Schempp
IAP, Frankfurt am Main, Germany

For hadron linacs RFQs are the first stage of acceleration. To reach high intensities a new Splitring-RFQ is investigated. Not only a high current and high beam quality/brilliance should be achieved, also a good tuning flexibility and comfort for maintenance are part of the study. It will consist of two stages with 27 MHz and 54 MHz to accelerate ions with an A/q of 60 up to energies of 200 keV/u. Therefor RF simulations with CST MWS were done to study the quality factor and the shunt impedance as well as tuning possibilities. First results and the status of the project will be presented.

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TUPIK007

VisualPIC: A New Data Visualizer and Post-Processor for Particle-in-Cell Codes

software, plasma, interface, GUI

1696

A. Ferran Pousa, R.W. Aßmann
DESY, Hamburg, Germany
A. Martinez de la Ossa
University of Hamburg, Hamburg, Germany

Numerical simulations are heavily relied on for evaluating optimal working points with plasma accelerators and for predicting their performance. These simulations produce high volumes of complex data, which is often analyzed by scientists with individually prepared software and analysis tools. As a consequence, there is a lack of a commonly available, quick, complete and easy-to-use data visualizer for Particle-In-Cell simulation codes. VisualPIC is a new application created with the aim of filling that void, providing a graphical user interface with advanced tools for 2D and 3D data visualization, post-processing and particle tracking. The program is developed under the principles of open source and with a modular design, an approach and architecture which allow interested scientists to contribute by adding new features or compatibility for additional simulation codes.

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TUPIK014

Detailed Analysis of a Linear Beam Transport Line from a Laser Wakefield Accelerator to a Transverse-Gradient Undulator

quadrupole, multipole, beam-transport, alignment

1711

A. Will, A. Bernhard, A.-S. Müller, C. Widmann
KIT, Karlsruhe, Germany
M. Kaluza
HIJ, Jena, Germany
M. Kaluza
IOQ, Jena, Germany

A linear beam transport system, experimentally tested at the Laser Wakefield Accelerator in Jena, Germany, has been carefully analyzed in order to gain a deeper understanding of the experimental results and to develop experimental strategies for the future. This analysis encompassed a detailed characterization of the focusing magnets and an investigation of the effects of source parameters as well as magnet and alignment errors on the observables accessible in the experiment. A dedicated tracking tool was developed for these investigations. In this contribution we review the main results of these studies.

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TUPIK018

Experimental Investigation of High Transformer Ratio Plasma Wakefield Acceleration at PITZ

plasma, wakefield, acceleration, experiment

1718

G. Loisch, P. Boonpornprasert, J.D. Good, M. Groß, H. Huck, M. Krasilnikov, O. Lishilin, A. Oppelt, Y. Renier, T. Rublack, F. Stephan
DESY Zeuthen, Zeuthen, Germany
G. Asova
INRNE, Sofia, Bulgaria
G. Asova, R. Brinkmann, A. Martinez de la Ossa, T.J. Mehrling, J. Osterhoff
DESY, Hamburg, Germany
F.J. Grüner
CFEL, Hamburg, Germany
F.J. Grüner, A. Martinez de la Ossa, T.J. Mehrling
University of Hamburg, Institut für Experimentalphysik, Hamburg, Germany

Plasma wakefield acceleration (PWFA), the acceleration of particles in a plasma wakefield driven by high current-density particle bunches, is one of the most promising candidates for a future compact accelerator technology. A key aspect of this type of acceleration is the ratio between the accelerating fields experienced by a witness beam and the decelerating fields experienced by the drive beam, called the transformer ratio. As for longitudinally symmetrical bunches this ratio is limited by the fundamental theorem of beamloading to 2 in the linear regime*, a transformer ratio above this limit is considered high. This can be reached by using a modulated drive bunch or a shaped train of drive bunches. So far, only the latter case has been shown for wakefields in a RF-structure**. We show the experimental setup, simulations and first, preliminary results of high transformer ratio acceleration experiments at the Photoinjector Test Facility at DESY in Zeuthen (PITZ).
* K. L. F. Bane, P. B. Wilson and T. Weiland, AIP Conference Proceedings 127, p. 875, 1984
** C. Jing et al., Physical Review Letters 98, 144801, 2007

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TUPIK024

Study of High Transformer Ratio Plasma Wakefield Acceleration for Accelerator Parameters of SXFEL Using 3D PIC Simulations

plasma, injection, acceleration, wakefield

1734

S. Huang, J.F. Hua, F. Li, W. Lu, C.H. Pai, Y. Wan, Y.P. Wu, S.Y. Zhou
TUB, Beijing, People's Republic of China
W. An, C. Joshi, W.B. Mori, X.L. Xu
UCLA, Los Angeles, California, USA
H.X. Deng, B. Liu, D. Wang, Z. Wang, Z.T. Zhao
SINAP, Shanghai, People's Republic of China

High transformer ratio (HTR) Plasma Wakefield Accelerator (PWFA) based on shaped electron bunches is an important topic of plasma wakefield acceleration for future light sources and colliders [1]. To explore the possibility of implementing PWFA at SXFEL, we performed 3D PIC simulations using shaped electron beam parameters obtained by start-to-end beam line simulations [2]. The PIC simulations show that an average transformer ratio around 4 can be maintained for about 10 cm long low density plasma, and the energy gain of the trailing bunch eventually reaches 5.9 GeV. Simulations and analysis are also performed to check the effects of transverse beam size on HTR acceleration. In addition, plasma density downramp injection has also been tested as a possible high brightness injection method for HTR acceleration, and preliminary results will be presented.
[*] Lu W, An W, Huang C, et al. High Transformer ratio PWFA for Applications on XFELs. Bulletin of the American Physical Society, 2009, 54.
[**] Z. Wang, Z. T. Zhao, et al. private communication

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TUPIK031

Driver-Witness-Bunches for Plasma-Wakefield Acceleration at the MAX IV Linear Accelerator

plasma, electron, linac, wakefield

1743

J. Björklund Svensson, H.E. Ekerfelt, O. Lundh
Lund University, Lund, Sweden
J. Andersson, F. Curbis, M. Kotur, F. Lindau, E. Mansten, S. Thorin, S. Werin
MAX IV Laboratory, Lund University, Lund, Sweden

Beam-driven plasma-wakefield acceleration is an acceleration scheme promising accelerating fields of at least two to three orders of magnitude higher than in conventional radiofrequency accelerating structures. The scheme relies on using a charged particle bunch (driver) to drive a non-linear plasma wake, into which a second bunch (witness) can be injected at an appropriate distance behind the first, yielding a substantial energy gain of the witness bunch particles. This puts very special demands on the machine providing the particle beam. In this article, we use simulations to show that, if driver-witness-bunches can be generated in the photo-cathode electron gun, the MAX IV Linear Accelerator could be used for plasma-wakefield acceleration.

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TUPIK037

Proton Cross-Talk and Losses in the Dispersion Suppressor Regions at the FCC-hh

proton, collimation, quadrupole, luminosity

1763

H. Rafique, R.B. Appleby
UMAN, Manchester, United Kingdom
J.L. Abelleira
JAI, Oxford, United Kingdom
A.M. Krainer, A. Langner
CERN, Geneva, Switzerland

Funding: The European Circular Energy-Frontier Collider Study (EuroCirCol), EU's Horizon 2020 grant No 654305
Protons that collide at the interaction points of the FCC-hh may contribute to the background in the subsequent detector. Due to the high luminosity of the proton beams this may be of concern. Using DPMJET-III to model 50 TeV proton-proton collisions, tracking studies have been performed with PTC and MERLIN in order to gauge the elastic and inelastic proton cross-talk. High arc losses, particularly in the dispersion suppressor regions, have been revealed. These losses originate mainly from particles with a momentum deviation, either from interaction with a primary collimator in the betatron cleaning insertion, or from the proton-proton collisions. This issue can be mitigated by introducing additional collimators in the dispersion suppressor region. The specific design, lattice integration, and the effect of these collimators on cross-talk is assessed.

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TUPIK048

Longitudinal Beam Stabilization at FAIR by Means of a Derivative Estimation

synchrotron, controls, experiment, dipole

1795

B.R. Reichardt, D. Domont-Yankulova
Technische Universität Darmstadt (TU Darmstadt, RMR), Darmstadt, Germany
D. Domont-Yankulova, H. Klingbeil
TEMF, TU Darmstadt, Darmstadt, Germany
H. Klingbeil, D.E.M. Lens
GSI, Darmstadt, Germany

Funding: Supported by the GSI
During acceleration in SIS18/SIS100 at GSI/FAIR longitudinal beam-oscillations are expected to occur. To reduce emittance blow-up, dedicated LLRF beam feedback systems are planned. To date longitudinal beam oscillations have been damped in machine experiments with a finite-impulse-response (FIR) filter controller with 3 filter taps[1]. An alternative approach implementing the FIR filter as a derivative estimator controller is simulated and tested. This approach shares the same controller topology and can therefore be easily integrated in the system. It exploits the fact that the sampling rate of the feedback hardware is considerably higher than the frequency of the beam oscillations. It is therefore capable of damping oscillations without overshoot within one oscillation period.

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TUPIK053

A Broadband Transverse Kicker Prototype for Intra-Bunch Feedback in the CERN SPS

kicker, impedance, feedback, coupling

1812

M. Wendt, I.A. Alonso Romero, S.J. Calvo, W. Höfle, O.R. Jones, E. Montesinos
CERN, Geneva, Switzerland

A transverse intra-bunch feedback system is currently under study at CERN for the SPS, to mitigate beam instabilities caused by electron clouds and coupled transverse modes (TMCI). This feedback system is designed for a bandwidth of 1 GHz, and based on a digital feedback controller and broadband power amplifiers. For the kicker, a periodic, quasi-TEM slotted transmission-line structure is foreseen which promises to meet the bandwidth requirements. This paper discusses the electromagnetic design and the mechanical implementation of a prototype kicker, demonstrating its performance and limitations based on numerical simulations.

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TUPIK066

Beam Loss Simulation and Radiation Shielding for Top-Off Operation of Hefei Light Source

electron, storage-ring, shielding, injection

1845

X. Zhou, J.Y. Li, J.G. Wang, S.W. Wang, W.B. Wu, W. Xu, K. Xuan, Q.B. Zeng
USTC/NSRL, Hefei, Anhui, People's Republic of China

The Hefei Light Source (HLS) is undergoing a series of upgrades to prepare for the top-off operation. To ensure radiation safety in the experimental hall under abnormal beam loss, simulations under various system errors in the HLS storage ring are performed to get in-depth understanding of the induced radiation nature. To make the radiation shielding more effective, a beam scraper is used to decrease the aperture opening of the vacuum chamber, and additional shielding is installed around the scraper. Simulation and beam test results are reported in this paper.

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TUPIK068

Parameters Calibration and Compensation-Rematch of Failure Cavities in CADS Injector

cavity, experiment, brightness, rfq

1852

Y.Z. Jia, W.L. Chen, W.P. Dou, P.H. Gao, H. Jia, S.H. Liu, Y.S. Qin, C. Wang, W.S. Wang, Z.J. Wang
IMP/CAS, Lanzhou, People's Republic of China

Now when a failure on the China Accelerator Driven System (CADS) is detected, the beam will be stopped by the machine protection system (MPS) immediately. But because of the demand of the beam trip (more than 5 min) rate which should be less than 50 times per year [1], it is important to avoid cutting beam down or recover the beam in a short time. The compensation and rematch is of great importance. If the failure is on a cavity, the other cavities should retune to compensate the beam energy, position and phase in order to recover the beam in short time depending on the time of online calculation.

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TUPIK075

ATF2 Beam Halo Collimation System Background and Wakefield Measurements in the 2016 Runs

collimation, wakefield, background, photon

1864

N. Fuster-Martínez, A. Faus-Golfe
IFIC, Valencia, Spain
P. Bambade, A. Faus-Golfe, S. Wallon, R.J. Yang
LAL, Orsay, France
K. Kubo, T. Okugi, T. Tauchi, N. Terunuma
Sokendai, Ibaraki, Japan
S. Kuroda
KEK, Ibaraki, Japan
I. Podadera, F. Toral
CIEMAT, Madrid, Spain
G.R. White
SLAC, Menlo Park, California, USA

A single vertical beam halo collimation system has been installed in ATF2 in March 2016 to reduce the background in the IP and Post-IP region. In this paper, we present the results of an experimental program carried out during 2016 in order to demonstrate the efficiency of the vertical collimation system and measure the wakefields induced by such a system. Furthermore, a comparison of the measurements of the collimation system wakefield impact with CST PS numerical simulations and analytical calculations is also presented.

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TUPIK076

Pre-Alignment Techniques Developments and Measurement Results of the Electromagnetic Center of Warm High-Gradient Accelerating Structures

alignment, linac, wakefield, target

1868

N. Galindo Munoz, N. Catalán Lasheras
CERN, Geneva, Switzerland
V.E. Boria
DCOM-iTEAM-UPV, Valencia, Spain
A. Faus-Golfe
IFIC, Valencia, Spain

Funding: PACMAN is founded under the European Union's 7th Framework Program Marie Curie Actions, grant PITN-GA-2013-606839
In the framework of the PACMAN project we have developed a test set-up to measure the electromagnetic centre of high gradient accelerating structures for alignment purposes. We have demonstrated with previous simulation studies that a resolution of 1 m is possible. The improvements applied on the technique and on the set-up, calibrations and the equipment instrumentation allows the measurement of the electromagnetic centre, with a final precision of 1.09 m in the horizontal plane and 0.58 m in the vertical plane. The experimental measurements and the simulation studies as a support to justify the numbers obtained are presented and discussed.

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TUPIK089

Studies on Luminous Region, Pile-up and Performance for HL-LHC Scenarios

luminosity, operation, optics, detector

1908

L.E. Medina Medrano, G. Arduini, R. Tomás
CERN, Geneva, Switzerland
L.E. Medina Medrano
UGTO, Leon, Mexico

Funding: Research supported by the HL-LHC project and the Beam project (CONACYT, Mexico).
Studies on luminous region and pile-up density are of great interest for the experiments at the future High Luminosity LHC (HL-LHC) in order to optimize the detector performance. The evolution of these parameters at the two main interaction points of the HL-LHC along optimum physics fills is studied for the baseline and alternative operational scenarios with the latest set of parameters, including a refined description of the longitudinal bunch profile. Results are discussed in terms of a new figure-of-merit, the effective pile-up density.

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TUPIK091

Simulation Tools for the Design and Performance Evaluation of Transverse Feedback Systems

feedback, framework, interface, pick-up

1912

J. Komppula, W. Höfle, K.S.B. Li
CERN, Geneva, Switzerland

Transverse feedback systems are used in synchrotrons and storage rings to damp injection oscillations and suppress transverse instabilities. Especially instabilities driven by high intensity beams in future circular colliders such as the FCC set challenging requirements for transverse feedback systems. In order to develop a transverse feedback system able to meet those requirements, sophisticated simulation tools are required. For this purpose, a new modular framework for modeling a transverse feedback system has been developed in Python. The framework can be used as a transverse feedback module in the macro-particle beam dynamics simulation code PyHEADTAIL or as a separate tool for studying a feedback model from a control theory point of view by using a simple signal models for the beam. The main principle of the code is presented and simulation methods used for the conceptual design of the FCC are discussed.

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TUPIK093

Sensitivity of the LHC Transverse Feedback System to Intra-Bunch Motion

feedback, pick-up, hardware, impedance

1916

G. Kotzian, W. Höfle, D. Valuch
CERN, Geneva, Switzerland

The LHC Transverse Feedback System is designed to damp and counteract all possible coupled bunch modes between the lowest betatron frequency and 20 MHz. The present study reveals that the analogue frontend processing scheme based on down converting the pick-up signal at the LHC RF frequency to baseband considerably extends the detected bunch movements visible to the feedback system to beyond 1 GHz. We develop an analytical model of the signal processing chain to explore the impact of even-symmetric and odd-symmetric intra-bunch movements on the detected beam position as a function of the longitudinal bunch shape. A set of equations is derived suitable for numerical simulations, or as a complement in particle tracking codes to further refine the behaviour of the LHC transverse feedback system.

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TUPIK098

Micrometric Propagation of Error Using Overlapping Streched Wires for the CLIC Pre-Alignment

network, alignment, linac, collider

1935

H. Mainaud Durand
CERN, Geneva, Switzerland
J. Pfingstner
University of Oslo, Oslo, Norway
V. Rude
ESGT-CNAM, Le Mans, France

The geodetic network for the Compact LInear collider (CLIC) will consist of a combination of overlapping wires stretched in parallel and Wire Positioning Sensors (WPS). Such a configuration will limit the propagation of errors (maximum deviation w.r.t. a fit line) below 10 micrometres over 200 metres. These first results were obtained through simulations in 2009, with hypotheses remaining to be validated. New experimental results have been obtained allowing to reconsider the precision and accuracy of WPS sensors and the knowledge of stretched wires. This paper presents the experimental results obtained on dedicated calibration benches and on a facility made of three overlapping stretched wires over a length of 140 metres including WPS sensors measurements. It confirms the possibility to have a propagation of error below 10 micrometres using overlapping stretched wires combined with WPS sensors.

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TUPIK100

Methodology Applied for Dependability Studies on the Compact Linear Collider

operation, quadrupole, linac, collider

1943

O. Rey Orozko, A. Apollonio, M. Jonker
CERN, Geneva, Switzerland

The Compact Linear Collider (CLIC) scheme presents several challenges in terms of reliability and availability. The goal of the study is to demonstrate the requirements for availability and reliability by identifying the key factors on failure effects and analysing possible operational scenarios and designs. Hence, a good knowledge on CLIC system structures, failure modes and failure effects is needed. This paper reports about the set-up of the studies from the definition of the CLIC failure catalogue to the implementation of the models and analysis of the results. It will present in detail the steps that need to be followed when performing such a study. Finally, the CLIC Drive Beam Quadrupoles powering system will be presented as a use-case.

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TUPIK111

IP Feedback Ground Motion Simulation Studies for the ILC

feedback, luminosity, ground-motion, collider

1983

R.M. Bodenstein, N. Blaskovic Kraljevic, T. Bromwich, P. Burrows, G.B. Christian, C. Perry, R.L. Ramjiawan
JAI, Oxford, United Kingdom
J. Pfingstner
CERN, Geneva, Switzerland

The International Linear Collider (ILC), as described in its Technical Design Report (TDR), must maintain strict control of its electron and positron beams in order to achieve the desired luminosity at each of its proposed center-of-mass energies. Controlling the beam parameters requires a dynamic system, capable of adjusting to a myriad of perturbations and errors. One of the components used to control the beam is the Interaction Point (IP) feedback system, which is used to dynamically steer the beams back into collision within nanoseconds. This work will show the simulation of the IP Feedback system's compensation for ground motion model K at the ILC.

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TUPIK114

First Experiences with the Longitudinal Feedback System at Diamond Light Source

cavity, feedback, kicker, hardware

1992

A.F.D. Morgan, M.G. Abbott, G. Rehm
DLS, Oxfordshire, United Kingdom

In order to avoid longitudinal multibunch instabilities potentially caused by the addition of normal conducting RF cavities into the Diamond storage ring, a longitudinal feedback was installed. The main components are newly developed feedback electronics, in-house built modulator and amplifier, and a low Q kicker cavity. This paper describes the performance of the cavity as well as the full longitudinal feedback system as it is installed on the machine and tested before the installation of the normal conducting RF cavities.

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TUPVA004

Synchrotron Radiation Backgrounds for the FCC-hh Experiments

photon, radiation, optics, collider

2031

F. Collamati
INFN-Roma1, Rome, Italy
M. Boscolo
INFN/LNF, Frascati (Roma), Italy
H. Burkhardt, R. Kersevan
CERN, Geneva, Switzerland

Funding: This work was supported by the HORIZON 2020 project EuroCirCol, grant agreement 654305.
We present in this paper a detailed analysis of the synchrotron radiation emitted by the 50 TeV protons of the FCC-hh in the last bending and quadrupole magnets upstream the interaction region. We discuss the characteristics of this radiation in terms of power, flux, photon spectrum and fans in different running conditions such as, for example, with and without crossing angle. We mainly focus our study on the fraction of photons that may hit the detector, with a full tracking into GEANT4 that simulates their interaction within the central beam pipe.

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TUPVA009

Multiparametric Response of the LHC Dynamic Aperture in Presence of Beam-Beam Effects

emittance, luminosity, optics, octupole

2051

D. Pellegrini, F. Antoniou, S.D. Fartoukh, G. Iadarola, Y. Papaphilippou
CERN, Geneva, Switzerland

We performed extended simulations of LHC dynamic aperture (DA) in the presence of beam-beam effects in the weak-strong approximation, evaluating the contributions of parameters such as: tunes, optics, bunch intensity, crossing angle, emittance, chromaticity and current in the Landau octupoles. Here we present a summary of these studies, giving an overview of the amplitude of the LHC operational space and pointing out the remaining margins for mitigation of instabilities. These studies supported the actions deployed during the 2016 run of the LHC, which aimed at maximising its performances. Examples of such actions are the switch to lower emittance beams, the reduction of crossing angle and tune trims. More recently, DA scans have been used to help the definition of the operational scenarios for the 2017 run. Additional room for improvements, for instance by deploying crossing angle levelling, will be explained.

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TUPVA010

Multiparametric Response of the HL-LHC Dynamic Aperture in Presence of Beam-Beam Effects

luminosity, octupole, beam-beam-effects, emittance

2055

D. Pellegrini, S.D. Fartoukh, N. Karastathis, Y. Papaphilippou
CERN, Geneva, Switzerland

We performed extended simulations of HL-LHC dynamic aperture in the presence of beam-beam effects in the weak- strong approximation, evaluating the contributions of param- eters such as: bunch intensity, crossing angle, chromaticity, current in the Landau octupoles and multipole errors. From the beam dynamics point of view, the main differ- ence between the LHC (until 2017) and the HL-LHC is the deployment of the achromatic telescopic squeezing (ATS) optics, allowing not only for a smaller '' reach, but also modifying the phase advances between the lattice correctors (sextupoles, octupoles) and the main IPs, and increasing the peak ' functions in the arcs. These correctors become therefore more efficient for the chromatic correction, but also a mitigation of the beam-beam long range interactions using the Landau octupoles is enabled, resulting in a possible reduction of the normalised crossing angle. The limits have been investigated in a tracking simulation campaign aimed at exploring the operational space for the HL-LHC and two possible options for luminosity levelling.

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TUPVA011

Comparing Behaviour of Simulated Proton Synchrotron Radiation in the Arcs of the LHC with Measurements

photon, synchrotron, synchrotron-radiation, radiation

2059

G. Guillermo Cantón, M. Ady, R. Kersevan, F. Zimmermann
CERN, Geneva, Switzerland
M. Angelucci, R. Cimino, E. La Francesca
INFN/LNF, Frascati (Roma), Italy
D. Sagan
Cornell University (CLASSE), Cornell Laboratory for Accelerator-Based Sciences and Education, Ithaca, New York, USA

Funding: EuCARD2 CONACyT
In previous work it was shown that at high proton-beam energies, synchrotron radiation is an important source of beam-screen heating, of beam-related vacuum pressure increase, and of primary photoelectrons, which can contribute to electron cloud formation. We have used the Synrad3D code developed at Cornell to simulate the photon distributions in the arcs of the LHC, HL-LHC, and FCC-hh. Specifically, for the LHC we studied the effect of the sawtooth chamber. In this paper specific results of the Synrad3D simulations are compared with simulations in Synrad+, developed at CERN; and later on compared with experimental data for actual LHC vacuum-chamber samples.

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TUPVA013

Lifetime of Asymmetric Colliding Beams in the LHC

luminosity, proton, coupling, ion

2067

J.M. Jowett, R. Alemany-Fernández, M.A. Jebramcik, T. Mertens, M. Schaumann
CERN, Geneva, Switzerland

In the 2013 proton-nucleus (p-Pb) run of the LHC, the lifetime of the lead beam was significantly shorter than could be accounted for by luminosity burn-off. These effects were observed at a lower level in 2016 and studied in more detail. The beams were not only asymmetric but the differences in the bunch filling schemes between protons and Pb nuclei led to a wide variety of beam-beam interaction sequences in the bunch trains. The colliding bunches were also of different sizes. We present an analysis of the data and an interpretation in terms of theoretical models.

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TUPVA018

Macroparticle Simulation Studies of the LHC Beam Dynamics in the Presence of Electron Cloud

electron, dipole, quadrupole, octupole

2081

A. Romano, G. Iadarola, K.S.B. Li, G. Rumolo
CERN, Geneva, Switzerland

Beam quality degradation caused by the Electron Cloud (EC) effects has been identified as one of the main performance limitations for the high intensity 25 ns beams in the Large Hadron Collider (LHC). When a proton bunch passes through an EC, electrons are attracted towards the transverse center of the beam resulting into an increasing electron density within the bunch. The effects driven by the interaction of the electrons with the bunch have been studied with macroparticle simulations in order to evaluate, in different operational scenarios, the threshold for the coherent instabilities as well as the incoherent tune spread. This contribution will summarize the main findings of the simulation study and compare them with the available experimental observations.

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TUPVA023

Effect of Quench Heater and CLIQ Firing on the Circulating HL-LHC Beam

dipole, quadrupole, collimation, superconducting-magnet

2101

M. Valette, L. Bortot, A.M. Fernandez Navarro, B. Lindstrom, R. Schmidt, A.P. Verweij, D. Wollmann
CERN, Geneva, Switzerland

Funding: Research supported by the HL-LHC project.
A small vertical orbit oscillation of the LHC beam was observed following a quench of a main dipole magnet. This effect was thought to be caused by the current dis-charged in the quench heater (QH) strips of the superconducting magnet and confirmed in dedicated experiments with beam in the LHC. Quench heater connection schemes with the largest effect have been identified for the LHC and its future HiLumi upgrade (HL-LHC). Furthermore, the impact on the beam following discharges of the Coupling-Loss Induced Quench (CLIQ) system, a novel technology to protect high current superconducting magnets in case of a quench, was studied to evaluate the possible failure cases.

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TUPVA026

Beam-Beam Studies for FCC-hh

optics, dynamic-aperture, luminosity, resonance

2109

J. Barranco García, T. Pieloni, C. Tambasco
EPFL, Lausanne, Switzerland
X. Buffat, S.V. Furuseth, C. Tambasco
CERN, Geneva, Switzerland
S.V. Furuseth
NTNU, Trondheim, Norway

Funding: This works was performed in the framework of the European Circular 'Energy Fr'ontier Collider Study, H2020 Framework Programme under grant agreement no. 654305. We acknowledge support from the Swiss State Secretariat for Education, Research and Innovation SERI.
The Future Circular Collider hadron-hadron (FCC-hh) design study is currently exploring different IR design possibilities including round and flat optics or different crossing schemes. The present study intends to evaluate each scenario from the beam-beam effects point of view. In particular the single particle long term stability to maximize beam lifetimes and luminosity reach is used to quantify the differences. The impact of strong head on interactions on the beam quality and lifetime is addressed by means of GPU accelerated simulations code featuring a weak-strong 6-dimensional beam-beam interaction.

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TUPVA029

Observations of Emittance Growth in the Presence of External Noise in the LHC

emittance, damping, brightness, experiment

2117

X. Buffat, C. Tambasco, D. Valuch
CERN, Geneva, Switzerland
J. Barranco García, T. Pieloni, C. Tambasco
EPFL, Lausanne, Switzerland

Dedicated experiments were perfomed in the LHC to study the impact of noise on colliding high brightness beams. The results are compared to theoretical models and multiparticle tracking simulations. The impacts on the LHC operation and the HL-LHC project are discussed.

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TUPVA030

Measurement of Beta-Beating Due to Strong Head-on Beam-Beam Interactions in the LHC

dipole, emittance, optics, injection

2121

P. Gonçalves Jorge, J. Barranco García, T. Pieloni
EPFL, Lausanne, Switzerland
X. Buffat, F.S. Carlier, J.M. Coello de Portugal, E. Fol, L.E. Medina Medrano, R. Tomás, A. Wegscheider
CERN, Geneva, Switzerland

The LHC operation relies on a good knowledge of the optics, usually corrected in absence of beam-beam interactions. In a near future, both the LHC and the HL-LHC will need to cope with large head-on beam-beam parameters, the impact on the optics needs to be understood and, if necessary, corrected. The results of a dedicated experiment performed at injection energy are discussed in this paper.

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TUPVA031

Impact of Incoherent Effects on the Landau Stability Diagram at the LHC

octupole, betatron, damping, coupling

2125

C. Tambasco, J. Barranco García, X. Buffat, T. Pieloni
CERN, Geneva, Switzerland
J. Barranco García, X. Buffat, T. Pieloni
EPFL, Lausanne, Switzerland

Instability thresholds are explored at the Large Hadron Collider (LHC) by means of the computation of the Landau Stability Diagrams (SD). In the presence of diffusive mechanisms, caused by resonance excitations or noise, the SD can be reduced due to the modification of the particle distribution inside the beam. This effect can lead to a possible lack of Landau damping of the coherent modes previously damped by lying within the unperturbed SD area. The limitations deriving from coherent instabilities in the LHC is crucial in view of future projects that aim to increase the performance of the LHC such as the High-Luminosity upgrade (HL-LHC). Simulation tools for the computation of the SD have been extended in order to take into account the incoherent effects from long tracking through the detailed model of the accelerator machine. The model includes among others beam-beam interactions and octupoles and the interplay between both is addressed. Finally the simulation results are compared to the Beam Transfer Function (BTF) measurements in the LHC.

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TUPVA032

Beam-Gas Background Observations at LHC

background, experiment, detector, luminosity

2129

S.M. Gibson
Royal Holloway, University of London, Surrey, United Kingdom
R. Alemany-Fernández, F. Alessio, G. Bregliozzi, H. Burkhardt, G. Corti, A. Di Mauro, M. Guthoff, A. Manousos, K.N. Sjobak, C. Yin Vallgren
CERN, Geneva, Switzerland
A. Alici
Bologna University, Bologna, Italy
S. D'Auria
University of Glasgow, Glasgow, United Kingdom
S.M. Gibson
JAI, Egham, Surrey, United Kingdom
D. Lazic
BUphy, Boston, Massachusetts, USA

Observations of beam-induced background at LHC during 2015 and 2016 are presented in this paper. The four LHC experiments use the non-colliding bunches present in the physics-filling pattern of the accelerator to trigger on beam-gas interactions. During luminosity production the LHC experiments record the beam-gas interactions using dedicated background monitors. These data are sent to the LHC control system and are used to monitor the background levels at the experiments during accelerator operation. This is a very important measurement, since poor beam-induced background conditions can seriously affect the performance of the detectors. A summary of the evolution of the background levels during 2015 and 2016 is given in these proceedings.

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TUPVA034

SPS Studies in Preparation for the Crab Cavity Experiment

emittance, experiment, luminosity, cavity

2133

A. Alekou, A. Alekou, F. Antoniou, F. Antoniou, G. Arduini, G. Arduini, H. Bartosik, H. Bartosik, R. Calaga, R. Calaga, Y. Papaphilippou, Y. Papaphilippou, Y. Papaphilippou
CERN, Geneva, Switzerland
A. Alekou, R.B. Appleby, R.B. Appleby
UMAN, Manchester, United Kingdom
R.B. Appleby, C.P. Welsch
Cockcroft Institute, Warrington, Cheshire, United Kingdom
C.P. Welsch
The University of Liverpool, Liverpool, United Kingdom

A local Crab Cavity (CC) scheme will recover head-on collisions at the Interaction Points (IPs) of the High Luminosity LHC (HL-LHC), which aims to increase the LHC luminosity by a factor of 3-10. The first time that CC will ever be tested with proton beams will be in 2018 in the SPS machine. The available dedicated Machine Development (MD) time after the installation of the cavities will be limited and therefore good preparation is essential in order to ensure that the MDs are as efficient as possible. This paper presents the simulations and experimental studies performed in preparation for the future MDs and discusses the next steps.

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TUPVA036

Cross-Talk Studies between FCC-hh Experimental Interaction Regions

detector, proton, collider, interaction-region

2136

J.L. Abelleira, A. Seryi
JAI, Oxford, United Kingdom
R.B. Appleby, H. Rafique
UMAN, Manchester, United Kingdom
M.I. Besana
CERN, Geneva, Switzerland

Funding: The European Circular Energy-Frontier Collider Study (EuroCirCol), EU's Horizon 2020 grant No 654305.
Debris from 50 TeV proton-proton collisions at the main interaction point in the FCC-hh may contribute to the background in the subsequent detector. This cross-talk is of possible concern for the FCC-hh due to the high luminosity and energy of the collider. DPMJET-III is used as a collision debris generator in order to assess the muon cross-talk contribution. An analytical calculation of muon range in rock is performed. This is followed by a full Monte Carlo simulation using FLUKA, where the accelerator tunnel has been modelled. The muon cross talk between the adjacent interaction points is assessed and its implications for FCC-hh design are discussed.

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TUPVA042

K-Modulation Developments via Simultaneous Beam Based Alignment in the LHC

quadrupole, optics, sextupole, closed-orbit

2159

L. van Riesen-Haupt, A. Seryi
JAI, Oxford, United Kingdom
J.M. Coello de Portugal, E. Fol, R. Tomás, R. Tomás
CERN, Geneva, Switzerland

Funding: EuroCirCol
A parasitic effect of k-modulation is that if the modulated quadrupole has an offset the modulation results in a dipole like kick forcing the beam on a new orbit. This paper presents a new method using the orthonormality of singular value decomposition that uses this new orbit to estimate the offset. This could be used to measure misalignments or crossing angles but could also help improve k-modulation \beta measurements by predicting the parasitic tune change caused by the new orbit not passing through the centre of the sextupoles.

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TUPVA047

IBS Simulation with Different RF Configurations in RHIC

emittance, cavity, proton, injection

2178

C. Liu, A.V. Fedotov, M.G. Minty, V. Ptitsyn
BNL, Upton, Long Island, New York, USA

Funding: Work supported by Brookhaven Science Associates, LLC under Contract No. DE-AC02-98CH10886 with the U.S. Department of Energy.
This report focuses on three dimensional emittance growth of polarized proton beam due to Intra-Beam Scattering (IBS) at RHIC. Simulations are presented which give guidance on the configuration of the RF systems to mitigate IBS-induced emittance growth. In addition, simulated growth rates are compared with measured emittance evolution at injection, which shows better agreement in longitudinal than transverse dimension. The results in this report will help us better understand the emittance evolution for current RHIC operations and for future operations (eRHIC).

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TUPVA048

Calculation of Particle Loss Maps for 2016 RHIC Gold-Gold Run

detector, operation, kicker, radiation

2181

Y. Luo, K.A. Drees, W. Fischer, X. Gu, A. Marusic, G. Robert-Demolaize, V. Schoefer
BNL, Upton, Long Island, New York, USA

Funding: Work supported by Brookhaven Science Associates, LLC under Contract No. DE-AC02-98CH10886 with the U.S. Department of Energy.
In the 2016 RHIC 100~GeV gold-gold (Au-Au) run, 20~mm orbit bumps were installed in the arcs to protect the experimental detectors from abort kicker prefiring. Chronic particle losses were observed in the arcs with these orbit bumps. Those particle losses are mainly from the 78+Au197 and 79+Au196 particles generated from bound-free pair production (BFPP) and electromagnetic dissociation (EMD) associated with the Au-Au collision at the IPs. In this article, we present simulated particle losses of 78+Au197 and 79+Au196 and calculate the particle loss distribution in the ring. The calculated particle loss maps are compared with operational observations.

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TUPVA061

Beam Dynamics Study for the HIM&GSI Heavy Ion SC CW-LINAC

cavity, linac, ion, acceleration

2217

S. Yaramyshev, W.A. Barth, M. Heilmann
GSI, Darmstadt, Germany
K. Aulenbacher
IKP, Mainz, Germany
K. Aulenbacher, W.A. Barth, V. Gettmann, M. Miski-Oglu
HIM, Mainz, Germany
W.A. Barth, S. Yaramyshev
MEPhI, Moscow, Russia
M. Basten, M. Busch, F.D. Dziuba, H. Podlech, M. Schwarz
IAP, Frankfurt am Main, Germany

A sc cw-linac with variable output energy from 3.7 to 7.5 MeV/u for ions with mass to charge ratio of A/Z<6 is recently under development at HIM and GSI. Following the results of the latest RF-tests with the newly constructed sc CH-DTL cavity, even heavier ions up to Uranium 28+ could be potentially accelerated with the already reached higher RF-voltage. Also the possibility for an up to 10 MeV/u increased output energy, using the same 13 independent cavities, is under consideration. All these options require an advanced beam dynamics layout, as well as a versatile procedure for transverse and longitudinal beam matching along the entire linac. The proposed algorithms are discussed and the obtained simulation results are presented.

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TUPVA068

The New Injector Design for MYRRHA

cavity, emittance, impedance, rfq

2234

K. Kümpel, P. Müller, D. Mäder, N.F. Petry, H. Podlech
IAP, Frankfurt am Main, Germany

The MYRRHA (Multi-purpose hYbrid Research Reactor for High-tech Applications) Project is a planned accelerator driven system (ADS) for the transmutation of long-living radioactive waste. A critical passage for the beam quality and especially for the emittance is the injector. Therefore, a new injector design with improved beam dynamics has been developed, featuring low emittance growth rates while using only room temperature structures. The previous design consisted of a 4-Rod RFQ, 7 room temperature and 5 superconducting CH-DTL cavities and 2 rebuncher cavities, whereas the superconducting cavities in the new design have been replaced by 8 room temperature CHs and an additional rebuncher. The main challenge during the development is achieving the required reliability to reduce the thermal stress inside the planned reactor. Therefore, simulations with CST MICROWAVE STUDIO have been made to compare several cooling concepts and to optimize the cavities, especially in terms of the shunt impedance.

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TUPVA070

Dipole Compensation of the 176 MHz MYRRHA RFQ

dipole, rfq, quadrupole, proton

2240

K. Kümpel, H.C. Lenz, N.F. Petry, H. Podlech
IAP, Frankfurt am Main, Germany
A. Bechtold
NTG Neue Technologien GmbH & Co KG, Gelnhausen, Germany
C. Zhang
GSI, Darmstadt, Germany

The MYRRHA (Multi-purpose hYbrid Research Reactor for High-tech Applications) Project is planned as an accelerator driven system (ADS) for the transmutation of long-living radioactive waste. For this project a cw 4-Rod-RFQ with 176 MHz and a total length of about 4 m is required. It is supposed to accelerate protons from 30 keV up to 1.5 MeV*. One of the main tasks during the development of the RFQ is the very high reliability of the accelerator to limit the thermal stress inside the reactor. Another challenge was to compensate the dipole component of the MYRRHA-RFQ which is due to the design principle of 4-Rod-RFQs. This dipole component is responsible for shifting the ideal beam axis from the geometrical center of the quadrupole downwards. Design studies with CST MICROWAVE STUDIO have shown that the dipole component can be almost completely compensated by widening the stems alternately so that the current paths of the lower electrodes are increased.
* C. Zhang, H. Podlech: NEW REFERENCE DESIGN OF THE EUROPEAN ADS RFQ ACCELERATOR FOR MYRRHA. In Proceedings of IPAC'14, 3223-3225 (2014)

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TUPVA074

Status of the modulated 3 MeV 325 MHz Ladder-RFQ

rfq, operation, linac, dipole

2249

M. Schütt, M.A. Obermayer, U. Ratzinger, M. Syha
IAP, Frankfurt am Main, Germany

Funding: BMBF 05P12RFRB9
Based on the positive results of the unmodulated 325 MHz Ladder-RFQ from 2013 to 2016, we develop a modulated 3.3 m Ladder-RFQ. The unmodulated Ladder-RFQ features a very constant voltage along the axis. It could withstand more than 3 times the operating power of which is needed in operation at a pulse length of 200μseconds. That corresponds to a Kilpatrick factor of 3. The 325 MHz RFQ is designed to accelerate protons from 95 keV to 3.0 MeV according to the design parameters of the p-linac at FAIR. This particularly high frequency for a 4-Rod-type RFQ creates difficulties, which are challenging in developing an adequate cavity. The results of the unmodulated prototype have shown, that the Ladder-RFQ is a suitable candidate for that frequency. Inspired by the successful rf power test, the nominal vane-vane voltage was increased from 80 kV to 96 kV. The basic design and tendering of the RFQ has been successfully completed in 2016. EM simulations of a modulated full structure, especially in terms of field-flatness and frequency tuning, will be shown. Furthermore, the mechanical design including a direct cooling of the structure for duty cycles up to about 5% will be discussed.

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TUPVA077

The Phase Slip Factor of the Electrostatic Cryogenic Storage Ring CSR

ion, storage-ring, quadrupole, cryogenics

2255

M. Grieser, R. Hahn, S. Vogel, A. Wolf
MPI-K, Heidelberg, Germany

For the determination of the momentum spread of an ion beam from the measurable revolution frequency distribution the knowledge of the phase slip factor of the storage ring is necessary. At various working points of the cryogenic storage ring CSR installed at the MPI for Nuclear Physics in Heidelberg the slip factor was simulated and compared with measurements. The predicted functional relationship of the slip factor and the horizontal tune depends on the different islands of stability, which has been experimentally verified. This behavior of the slip factor is in clear contrast to magnetic storage rings. In the paper we compare the results of the simulations with the measurements

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TUPVA079

Model of Statistical Errors in the Search for the Deuteron EDM in the Storage Ring

detector, experiment, scattering, dipole

2258

A.E. Aksentyev, V. Senichev
FZJ, Jülich, Germany

In this work we investigate the standard error of the spin precession frequency estimate in an experiment for the search for the electric dipole moment (EDM) of the deuteron using the polarimeter. The basic principle of polarimetry is the scattering of a polarized beam on a carbon target. Since the number of particles in one fill is limited, we must maximize the utility of the beam. This raises the question of sampling efficiency, as the signal, being an oscillating function, varies in informational content. To address it, we define a numerical measurement model, and compare two sampling strategies (uniform and frequency-modulated) in terms of beam-use efficiency. The upshot is the formulation of the conditions necessary for the effective use of the modulated sampling strategy, and the evaluation of its advantage over the uniform strategy. The simulation results are also used to compare two competing analytical models for the standard error of the frequency estimate.

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TUPVA082

Spin Tracking for a Deuteron EDM Storage Ring

lattice, storage-ring, dipole, quadrupole

2267

Al.Alb. Skawran, A. Lehrach
FZJ, Jülich, Germany

The purpose of the Jülich Electric Dipole moment Investigations (JEDI) collaboration is the measurement of the electric dipole moment (EDM) of charged particles like deuterons. There are two possible experimental setups under consideration for realization of this measurement with deuterons: The Frozen and Quasi Frozen Spin storage ring experiments. Both approaches are discussed and compared in this presentation. Various misalignments and systematic effects are simulated in the context of comparison. Furthermore the clockwise-counterclockwise method (CW-CCW) is applied and checked for its validity.

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TUPVA083

Analysis of Closed-Orbit Deviations for a First Direct Deuteron Electric Dipole Moment Measurement at the Cooler Synchrotron COSY

closed-orbit, dipole, power-supply, quadrupole

2271

V. Schmidt, A. Lehrach
FZJ, Jülich, Germany

This presentation investigates closed orbit influencing effects focusing on transverse orbit deviations. Using a model of the Cooler Synchrotron COSY at the Forschungszentrum Jülich implemented in the Methodical Accelerator Design program, several magnet misalignments are simulated and analyzed. A distinction is made between magnet displacements along the axes and rotations around them. Results are always analyzed for the uncorrected as well as for the orbit after the application of an orbit correction. Furthermore, the effect of displaced beam position monitors is simulated and a constraint resolution of their readout is considered. Besides magnet misalignments also field variations resulting from residual power supply oscillations are quantified for all types of magnets.

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TUPVA089

Preliminary Design of a High-intensity Continuous-wave Deuteron RFQ

rfq, emittance, linac, focusing

2287

X. Liu
RIKEN, Saitama, Japan
O. Kamigaito, N. Sakamoto, K. Yamada
RIKEN Nishina Center, Wako, Japan

Funding: This work has been funded by ImPACT Program of Council for Science, Technology and Innovation (Cabinet Office, Government of Japan)
A high-intensity deuteron linear accelerator is currently beding studied as a promising candidate to treat high-level radioactive wastes through the nuclear transmutation process. This paper presents the study on a design of a 75.5 MHz, 400 mA, continuous-wave deuteron radio-frequency quadrupole (RFQ), which is proposed as the front-end of such a linear accelerator. The results of the beam dynamics simulation suggest that the designed RFQ can accelerate a 400-mA deuteron beam from 100 keV to 2.5 MeV with a transmission rate of 92 ~ 93.3%, depending on the assumed input transverse emittance.

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TUPVA094

Beam Dynamics Design of the Muon Linac High-Beta Section

linac, emittance, impedance, target

2304

Y. Kondo, K. Hasegawa
JAEA/J-PARC, Tokai-mura, Japan
R. Kitamura
University of Tokyo, Tokyo, Japan
T. Mibe, M. Otani, M. Yoshida
KEK, Tsukuba, Japan

Funding: This work was supported by JSPS KAKENHI Grant Number 16H03987.
A muon linac development for a new muon g-2 experiment is now going on at J-PARC. Muons from the muon beam line (H-line) at the J-PARC MLF are once stopped in an silica aerojel target and room temperature muoniums are evaporated from the aerogel. They are dissociated with laser (ultra slow muons), then accelerated up to 212 MeV using a linear accelerator. For the accelerating structure from 40 MeV, disk-loaded traveling-wave structure is applicable because the particle beta is more than 0.7. The structure itself is similar to that for electron linacs, however, the cell length should be harmonic to the increase of the particle velocity. In this paper, the beam dynamics design of this muon linac using the disk-loaded structure is described.

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TUPVA099

Preparation for the CSNS-RCS Commissioning

quadrupole, lattice, dipole, proton

2317

Y.W. An, Y.D. Liu, Y. Liu, S. Wang, S.Y. Xu
IHEP, Beijing, People's Republic of China

Funding: Work supported by National Natural Science Foundation of China (11405189)
As a key part of the China Spallation Neutron Source (CSNS) Project, the Rapid Cycling Synchrotron (RCS) accumulates and accelerates the proton beam from 80MeV to 1.6GeV for extracting and striking the target with a repetition rate of 25Hz. As a commissioning plan, the BPM offset should be carefully investigated before closed orbit distortion (COD) correction. The fast response correctors are installed to correct orbit distortion and model the lattice of the RCS in every 1ms period. The bunch-by-bunch data from BPMs are collected and decomposed for better known of the RCS Lattice.

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TUPVA101

Study of Different Models on DTL for CSNS

DTL, linac, emittance, alignment

2322

Y. Yuan, Z.P. Li, J. Peng
IHEP, Beijing, People's Republic of China

China Spallation Neutron Source (CSNS) is a high intensity accelerator based facility. Its accelerator consists of an H⁻ injector and a proton Rapid Cycling Synchrotron (RCS). The injector includes the front end and linac. The RFQ accelerates the beam to 3MeV, and then the Drift Tube Linac (DTL) accelerates it to 80MeV. A Medium Energy Beam Transport (MEBT) matches RFQ and DTL, and the DTL consists of four tanks (DTL1, 2, 3, 4). A Linac to Ring Beam Transport (LRBT) matches DTL and RCS, also decreases beam energy spread. Commissioning of the first three DTL tank and LRBT straight section have been almost accomplished in this run. This paper takes a beam dynamics simulation on beam transport in MEBT and DTL at different DTL accelerate models. Meanwhile, beam's central orbit deviation at DTL and LRBT straight section due to DTL mechanical cavity's alignment errors is studied with IMPACT-Z code.

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TUPVA103

Beam Dynamics Design of the 3MeV RFQ for BISOL Project

rfq, emittance, neutron, linac

2328

H.P. Li, Q. Fu, P.P. Gan, Y.R. Lu, Z. Wang, K. Zhu
PKU, Beijing, People's Republic of China

The Beijing isotope separation online (BISOL) facility will be used to study the new physics and technologies at the limit of nuclear stability. The facility can be driven by a reactor or a deuteron accelerator. The driver accelerator for the BISOL facility aims to accelerate a 50 mA D⁺ beam to 40 MeV. As an injector for the downstream su-perconducting linac, a 4-vane RFQ operating at 162.5 MHz has been designed to accelerate the deuteron beam from 0.05 MeV to 3.0 MeV in CW mode. For the beam dynamics design of this high-intensity RFQ, a matched and equipartitioned design method is adopted in order to control beam loss. After the optimization, the simulated beam transmission efficiency is higher than 99%. The transverse normalized rms emittance growth is approxi-mately 12%. Detailed results of the beam dynamics as well as the error study of the RFQ are presented in this paper.

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TUPVA104

RF and Primary Beam Dynamics Design of a 325 MHz IH-DTL

DTL, cavity, proton, linac

2332

Y. Lei, X. Guan, C.-X. Tang, R. Tang, X.W. Wang, Q.Z. Xing, S.X. Zheng
TUB, Beijing, People's Republic of China

An interdigital H-mode drift tube linac (IH-DTL), which is aimed at proton medical facilities, has been proposed and developing at Tsinghua University. Considering following 3 MeV RFQ in the platform of CPHS (Compact Pulse Hadron Source at Tsinghua University) and XiPAF (Xi‘an Proton Application Facility) project, the input energy of IH-DTL is 3 MeV and the RF frequency is 325 MHz. The proton beam can be accelerated from 3 MeV to 7 MeV and the peak current of the beam at the exit of the cavity is about 15 mA. In order to simplify the fabrication, A KONUS structure without focusing element in the cavity is chosen. The RF design of single CELL and the primary dynamics design is done. The co-iteration of dynamics simulation and RF calculation of whole cavity is undergoing.

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TUPVA115

Progress with Long-Range Beam-Beam Compensation Studies for High Luminosity LHC

electron, cathode, proton, optics

2358

A. Rossi, O. Aberle, J. Albertone, A. Bertarelli, C.B. Boccard, F. Carra, G. Cattenoz, Y. Delaup, S.D. Fartoukh, G. Gobbi, J. Lendaro, Y. Papaphilippou, D. Perini, S. Redaelli, H. Schmickler, C. Zanoni
CERN, Geneva, Switzerland
A.M. Barnyakov, A.E. Levichev, D.A. Nikiforov
BINP SB RAS, Novosibirsk, Russia
M. Fitterer, A.S. Patapenka, G. Stancari, A. Valishev
Fermilab, Batavia, Illinois, USA

Long-range beam-beam (LRBB) interactions can be a source of emittance growth and beam losses in the LHC during physics and will become even more relevant with the smaller '* and higher bunch intensities foreseen for the High Luminosity LHC upgrade (HL-LHC), in particular if operated without crab cavities. Both beam losses and emittance growth could be mitigated by compensat-ing the non-linear LRBB kick with a correctly placed current carrying wire. Such a compensation scheme is currently being studied in the LHC through a demonstration test using current-bearing wires embedded into col-limator jaws, installed either side of the high luminosity interaction regions. For HL-LHC two options are considered, a current-bearing wire as for the demonstrator, or electron lenses, as the ideal distance between the particle beam and compensating current may be too small to allow the use of solid materials. This paper reports on the ongoing activities for both options, covering the progress of the wire-in-jaw collimators, the foreseen LRBB experiments at the LHC, and first considerations for the design of the electron lenses to ultimately replace material wires for HL-LHC.

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TUPVA120

Design and Fabrication of ESS-Bilbao RFQ Linac

rfq, cavity, vacuum, proton

2373

J.L. Muñoz, I. Bustinduy, I. Rueda, D. de Cos
ESS Bilbao, Zamudio, Spain

The RFQ accelerator for ESS-Bilbao is presented. This device will complete ESS-Bilbao injection chain after the ion source and LEBT. Design, carried out by ESS-Bilbao team, was finished in 2015. Machining has started in 2016. The RFQ is a 4-vane structure, aimed to accelerate protons from 45 keV to 3.0 MeV and operating at 352.2 MHz. It has a total length of about 3.1 meters, divided in 4 segments. Segments themselves are formed by 2 major and 2 minor vanes, assembled together by using polymeric vacuum gaskets instead of brazing or other welding system. In this paper the design is presented, including the beam dynamics, RF cavity design, field flatness and frequency tuning. Cooling and thermo-mechanical design is also described. Mechanical design, including vacuum strategy and test models, is also briefly described (there is a dedicated poster on this). The first segment fabrication is scheduled to finish before the end of 2016, so vacuum and low power RF tests results would also be included in the presented paper.

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TUPVA133

Thin Internal Target Studies in a Compact FFAG

target, scattering, emittance, proton

2411

D. Bruton, R.J. Barlow, T.R. Edgecock
University of Huddersfield, Huddersfield, United Kingdom
C. Johnstone
PAC, Batavia, Illinois, USA

The production of radioisotopes using a thin internal target and recycled beam within a compact FFAG design has been studied. Radioisotopes have a wide range of uses in medicine, and recent disruption to the supply chain has seen a renewed effort to find alternative isotopes and production methods. The FFAG design features separate sector magnets with non-scaling, non-linear field gradients which are optimized with magnet geometry to achieve isochronisity at the level of 0.3%, sufficient for Continuous Wave (CW) operation. Simulations have demonstrated that beam currents of up to 10mA can comfortably be achieved with this design. To further improve production efficiency a thin internal target, where the beam passes through the target and is recirculated, may be used. This setup ensures that production takes place within a narrow energy range, potentially increasing production rates and reducing impurities.

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TUPVA136

Using Sloppy Models for Constrained Emittance Minimization at the Cornell Electron Storage Ring (CESR)

emittance, lattice, storage-ring, coupling

2418

W.F. Bergan, A.C. Bartnik, I.V. Bazarov, H. He, D. L. Rubin
Cornell University (CLASSE), Cornell Laboratory for Accelerator-Based Sciences and Education, Ithaca, New York, USA
J.P. Sethna
Cornell University, Ithaca, New York, USA

Funding: DOE DE-SC0013571 NSF DGE-1144153
In order to minimize the emittance at the Cornell Electron Storage Ring (CESR), we measure and correct the orbit, dispersion, and transverse coupling of the beam.* However, this method is limited by finite measurement resolution of the dispersion, and so a new procedure must be used to further reduce the emittance due to dispersion. In order to achieve this, we use a method based upon the theory of sloppy models.** We use a model of the accelerator to create the Hessian matrix which encodes the effects of various corrector magnets on the vertical emittance. A singular value decomposition of this matrix yields the magnet combinations which have the greatest effect on the emittance. We can then adjust these magnet ‘‘knobs'' sequentially in order to decrease the dispersion and the emittance. We present here comparisons of the effectiveness of this procedure in both experiment and simulation using a variety of CESR lattices. We also discuss techniques to minimize changes to parameters we have already corrected.
* J. Shanks, D.L. Rubin, and D. Sagan, Phys. Rev. ST Accel. Beams 17, 044003 (2014).
** K.S. Brown and J.P. Sethna, Phys. Rev. E 68, 021904 (2003).

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TUPVA140

Space charge effects of catch-up collision in a CW double-pass proton linac

linac, proton, cavity, space-charge

2429

Y. Tao, K. Hwang, J. Qiang
LBNL, Berkeley, California, USA

Recirculating superconducting proton linac has an advantage to reduce the number of cavities and the resulting accelerator construction/operation costs. Beam dynamics simulations were done recently in a double pass recirculating proton linac using a single bunch. For continuous wave (CW) operation, the high energy proton beam bunch during the second pass will catch up and collide with the low energy proton bunch at a number of locations inside the superconducting linac. In this paper, we report on the study of the space-charge effects during a collision on both beams through the rest of the linac.

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TUPVA146

6D Phase Space Measurement of Low Energy, High Intensity Hadron Beam

experiment, hadron, dipole, quadrupole

2441

B.L. Cathey
ORNL RAD, Oak Ridge, Tennessee, USA
A.V. Aleksandrov, S.M. Cousineau, A.P. Zhukov
ORNL, Oak Ridge, Tennessee, USA

Funding: SNS is managed by UT-Battelle, LLC, under contract DE-AC05-00OR22725 for the U.S. Department of Energy. The work has been partially supported by NSF grant 1535312
The goal of this experiment is to measure the full 6D phase space of a low energy, high intensity hadron beam. We use 4D emittance measurement techniques for the transverse plane combined with dispersion measurement and a beam shape monitor to provide the longitudinal phase space. The Beam Testing Facility (BTF) at the Spallation Neutron Source (SNS), a 2.5 MeV functional duplicate front end of the SNS accelerator is being used to facilitate the measurement. Early 6D measurements will be presented.

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TUPVA148

FODO Lattice Design for Beam Halo Research at SNS

lattice, quadrupole, rfq, experiment

2449

Z.L. Zhang
ORNL RAD, Oak Ridge, Tennessee, USA
A.V. Aleksandrov, S.M. Cousineau
ORNL, Oak Ridge, Tennessee, USA

Beam halo is a big challenge for high intensity accelerators. Knowledge of the mechanisms of halo formation could help to prevent it. The Spallation Neutron Source (SNS) Beam Test Facility (BTF) is a functional duplicate of the SNS front end with enhanced diagnostics capable of accelerating 50 mA H⁻ or protons to 2.5 MeV. To explore halo development in both matched and mismatched beams, a dedicated FODO lattice is being designed as an extension to the BTF. The FODO lattice will be 3.5 meters in length and is comprised of 16 quadrupole magnets, with dedicating matching magnets. Simulations of the design lattice show halo can be seen clearly in the phase space density plot when beam is mismatched. Details of the FODO design will be presented in the paper.

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WEOBA1

A Comparison of Interaction Physics for Proton Collimation Systems in Current Simulation Tools

collimation, proton, collider, scattering

2478

J. Molson, A. Faus-Golfe
LAL, Orsay, France
R.B. Appleby, S.C. Tygier
UMAN, Manchester, United Kingdom
R.J. Barlow
IIAA, Huddersfield, United Kingdom
R. Bruce, F. Cerutti, A. Ferrari, A. Mereghetti, S. Redaelli, K.N. Sjobak, V. Vlachoudis
CERN, Geneva, Switzerland
H. Rafique
University of Manchester, Manchester, United Kingdom
Y. Zou
IHEP, Beijing, People's Republic of China

Funding: The European Circular Energy-Frontier Collider Study (EuroCirCol) project has received funding from the European Union's Horizon 2020 research and innovation programme under grant No 654305.
High performance collimation systems are required for current and proposed high energy hadron accelerators in order to protect superconducting magnets and experiments. In order to ensure that the collimation system designs are sufficient and will operate as expected, precision simulation tools are required. This paper discusses the current status of existing collimation system tools, and performs a comparison between codes in order to ensure that the simulated interaction physics between a proton and a collimator jaw is accurate.

Slides WEOBA1 [7.235 MB]

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WEOBA2

Hollow Electron Beam Collimation for HL-LHC - Effects on the Beam Core

electron, emittance, experiment, operation

2482

M. Fitterer, G. Stancari, A. Valishev
Fermilab, Batavia, Illinois, USA
R. Bruce, G. Papotti, S. Redaelli, D. Valuch, C. Xu
CERN, Geneva, Switzerland
G. Valentino
University of Malta, Information and Communication Technology, Msida, Malta

Funding: Fermilab is operated by Fermi Research Alliance, LLC, under Contract DE-AC02-07CH11359 with the US Department of Energy.
Collimation with hollow electron beams is currently one of the most promising concepts for active halo control in the High Luminosity Large Hadron Collider (HL-LHC). To ensure the successful operation of the hollow beam collimator the unwanted effects on the beam core, which might arise from the operation with a pulsed electron beam, must be minimized. This paper gives a summary of the effect of hollow electron lenses on the beam core in terms of sources, provides estimates for HL-LHC and discusses the possible mitigation methods.

Slides WEOBA2 [2.074 MB]

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WEOBA3

Studies of a Scheme for Low Emittance Muon Beam Production From Positrons on Target

target, positron, emittance, scattering

2486

M. Boscolo, M. Antonelli, M.E. Biagini, O.R. Blanco-García, A. Variola
INFN/LNF, Frascati (Roma), Italy
A. Bacci
Istituto Nazionale di Fisica Nucleare, Milano, Italy
I. Chaikovska, R. Chehab
LAL, Orsay, France
F. Collamati
INFN-Roma1, Rome, Italy
M. Iafrati
ENEA, Agenzia nazionale per le nuove tecnologie, l'energia e lo sviluppo economico sostenibile, Frascati, Italy
L. Keller
SLAC, Menlo Park, California, USA
S.M. Liuzzo, P. Raimondi
ESRF, Grenoble, France
P. Sievers
CERN, Geneva, Switzerland

We are studying a new scheme to produce very low emittance muon beams using a positron beam of about 45 GeV interacting on electrons on target. This is a challenging and innovative scheme that needs a full design study. One of the innovative topics to be investigated is the behaviour of the positron beam stored in a low emittance ring with a thin target, that is directly inserted in the ring chamber to produce muons. Muons will be immediately collected at the exit of the target and transported to two mu+ and mu- accumulator rings. We focus in this paper on the simulation of the e⁺ beam interacting with the target, its degradation in the 6-D phase space and the optimization of the e⁺ ring design mainly to maximize the energy acceptance. We will investigate the performances of this scheme, ring optics plus target system, comparing different multi-turn simulations.

Slides WEOBA3 [3.737 MB]

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WEXB1

Studies and Observations of Beam Dynamics Near a Sum Resonance

resonance, space-charge, synchrotron, emittance

2503

G. Franchetti
GSI, Darmstadt, Germany
S.S. Gilardoni, A. Huschauer, F. Schmidt, R. Wasef
CERN, Geneva, Switzerland

The effect of space charge on bunches stored for long term in a can be severe for beam survival. This may be the case in projects as SIS100 at GSI or LIU at CERN. In the past decade systematic simulation studies and experiments performed at CERN and GSI have highlighted the space charge induced periodic crossing of Â“one dimensionalÂ” resonances as the underlying mechanism of long term beam loss or emittance growth. However only in 2012, for the first time, the effect of space charge on a normal third order coupled resonance was investigated at the CERN-PS. The experimental results have highlighted an unprecedented asymmetric beam response where in the horizontal plane the beam exhibits a thick halo, whereas the vertical profile has only core growth. The quest for explaining these results requires a journey thorough the 4 dimensional dynamics of the coupled resonance investigating the fix-lines, and requires a detailed code-experiment benchmarking also including beam profile benchmarking. This study shows that the experimental results of the 2012 PS measurements can be explained by the dynamics the fixed lines also including the effect of the dispersion.

Slides WEXB1 [18.195 MB]

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WEOAB3

RF Quadrupole Structures for Transverse Landau Damping in Circular Accelerators

quadrupole, damping, impedance, collider

2516

M. Schenk, X. Buffat, L.R. Carver, A. Grudiev, K.S.B. Li, E. Métral, K. Papke
CERN, Geneva, Switzerland
A. Maillard
ENS, Paris, France

The beams required for the high luminosity upgrade of the Large Hadron Collider (HL-LHC) and other potential future circular colliders (FCC) call for efficient mechanisms to suppress transverse collective instabilities. In addition to octupole magnets installed for the purpose of Landau damping in the transverse planes, we propose to use radio frequency (rf) quadrupole structures to considerably enhance the aforementioned stabilising effect. By means of the PyHEADTAIL macroparticle tracking code as well as analytical studies, the stabilising mechanism introduced by an rf quadrupole is studied and explained. It is, furthermore, compared to the influence of the second order chromaticity on transverse beam stability.

Slides WEOAB3 [2.537 MB]

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WEYB1

Towards a Fully Integrated Accelerator on a Chip: Dielectric Laser Acceleration (DLA) From the Source to Relativistic Electrons

laser, electron, acceleration, emittance

2520

K.P. Wootton, R.J. England, S.G. Tantawi
SLAC, Menlo Park, California, USA
R.W. Aßmann, I. Hartl, W. Kuropka, F. Mayet, A. Rühl
DESY, Hamburg, Germany
D.S. Black, R.L. Byer, H. Deng, S. Fan, J.S. Harris, T.W. Hughes, N. Sapra, O. Solgaard, J. Vuckovic
Stanford University, Stanford, California, USA
B.M. Cowan
Tech-X, Boulder, Colorado, USA
T. Egenolf, U. Niedermayer
TEMF, TU Darmstadt, Darmstadt, Germany
P. Hommelhoff, A. Li, N. Schönenberger
University of Erlangen-Nuremberg, Erlangen, Germany
J. Illmer, J.C. McNeur, A.K. Mittelbach, A.D. Tafel
Friedrich-Alexander Universität Erlangen-Nuernberg, University Erlangen-Nuernberg LFTE, Erlangen, Germany
R. Ischebeck, L. Rivkin
PSI, Villigen PSI, Switzerland
F.X. Kärtner
MIT, Cambridge, Massachusetts, USA
F.X. Kärtner
CFEL, Hamburg, Germany
W. Kuropka, F. Mayet
University of Hamburg, Institut für Experimentalphysik, Hamburg, Germany
Y.J. Lee, M. Qi
Purdue University, West Lafayette, Indiana, USA
P. Musumeci
UCLA, Los Angeles, California, USA
L. Rivkin
EPFL, Lausanne, Switzerland

Funding: This work was supported by the U.S. Department of Energy, Office of Science, under Contract no. DE-AC02-76SF00515, and by the Gordon and Betty Moore Foundation under grant GBMF4744 (Accelerator on a Chip).
Dielectric laser acceleration of electrons has recently been demonstrated with significantly higher accelerating gradients than other structure-based linear accelerators. Towards the development of an integrated 1 MeV electron accelerator based on dielectric laser accelerator technologies, development in several relevant technologies is needed. In this work, recent developments on electron sources, bunching, accelerating, focussing, deflecting and laser coupling structures are reported. With an eye to the near future, components required for a 1 MeV kinetic energy tabletop accelerator producing sub-femtosecond electron bunches are outlined.

Slides WEYB1 [12.774 MB]

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WEPAB001

Parallel Operation of SASE1 and SASE3 Undulator Sections of European XFEL

radiation, undulator, kicker, operation

2554

A. Sargsyan, V. Sahakyan
CANDLE SRI, Yerevan, Armenia
W. Decking
DESY, Hamburg, Germany

In the current paper the numerical simulation results for parallel (decoupled) operation of SASE1 and SASE3 undulator sections of European XFEL are presented. The study was based on the idea of betatron switcher imple-mentation. It was shown that it is possible to avoid energy spread growth in SASE1 and to reach the saturation in SASE3 in desirable range of radiation wavelengths by a trajectory kick before SASE1 and its correction before SASE3.

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WEPAB005

First MOGA Optimization of the Soleil Lattice

lattice, storage-ring, injection, synchrotron

2568

L.S. Nadolski, P. Brunelle, X.N. Gavaldà
SOLEIL, Gif-sur-Yvette, France

The first optimization of the nonlinear beam dynamics of the SOLEIL synchrotron radiation light sources using Multi-Objective Genetic Algorithm is reported. After benchmarking ELEGANT against TRACY3, beam lifetime studies with the operation lattice and fine-tuning of the storage ring model, MOGA-ELEGANT was used to find the best settings of quadrupole and sextupole magnets in order to maximize the dynamic and momentum apertures used as proxies for the Touschek lifetime and the injection efficiency respectively. The solutions obtained after one month of computation in the high level computational cluster of SOLEIL using 200 CPUs are detailed. The improvement of the Touschek lifetime obtained with MOGA is confirmed by the beam-based experiments. The beam lifetime of the SOLEIL storage ring was increased experimentally by 40% as predicted by the simulations.

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WEPAB020

Beam Loss Simulations for the Implementation of the Hard X-Ray Self-Seeding System at European XFEL

undulator, electron, collimation, neutron

2611

S. Liu, W. Decking, L. Fröhlich
DESY, Hamburg, Germany

The European XFEL is designed to be operated with a nominal beam energy of 17.5 GeV at a maximum repetition rate of 27000 bunches/second. The high repetition rate together with the high loss sensitivity of the undulators raises serious radiation damage concern, especially for the implementation of the Hard X-ray Self-Seeding (HXRSS) system, where a 100 um thick diamond crystal will be inserted close to the beam in the undulator section. Since the seeding power level highly depends on the delay of the electron beam with respect to the photon beam, it is crucial to define the minimum electron beam offset to the edge of the crystal in the HXRSS chicane. At European XFEL a ~200 m long post-linac collimation section has been designed to protect the undulators. In the HXRSS scheme, however, beam halo hitting the crystal can generate additional radiation. Particle tracking simulations have been performed using GEANT4 and BDSIM for the undulator and the collimation section, respectively. The critical number of electrons allowed to hit the crystal is estimated for a certain operation mode and the efficiency of beam halo collimation is investigated to predict the minimum HXRSS chicane delay.

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WEPAB026

BRho-Dependent Taylor Transfer Maps for Super-FRS Dipole Magnets

dipole, ion, radiation, multipole

2631

E.S. Kazantseva, O. Boine-Frankenheim
TEMF, TU Darmstadt, Darmstadt, Germany
M. Berz, R. Jagasia, K. Makino
MSU, East Lansing, Michigan, USA
H. Weick, J.S. Winfield
GSI, Darmstadt, Germany

The Super-FRS is an in-flight projectile fragment separator being built at GSI for FAIR. Due to the required high design momentum resolution and large acceptance (Ah= ±40mrad, Av= ±20mrad) the dipole magnets of the Super-FRS have large apertures (38×14cm²). The wide design magnetic rigidity (BRho) range 2-20 Tm requires the variation of the main dipole magnetic field B0 in the range 0.16-1.6 T. Since the upper third of the B0 range is situated in a non-linear saturation region of the magnetization curve B(H) and the spatial distribution of magnetic permeability in the steel yoke is non-uniform, the field distribution in the useful aperture of the magnet is a non-linear and non-uniform function of the excitation current I. One consequence is the shortening of the effective length and the change of the field distribution with increasing I. In this study we analyze these effects for the Super-FRS dipole magnets. We use 3D field distribution from FEM simulations for different I values and a resulting BRho(I). From the fields the Taylor transfer maps for the particles are obtained using DA techniques (COSY-infinity) and the convergence of the resulting transfer maps is discussed.

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WEPAB031

OCELOT as a Framework for Beam Dynamics Simulations of X-Ray Sources

wakefield, FEL, space-charge, electron

2642

S.I. Tomin
XFEL. EU, Hamburg, Germany
I.V. Agapov, M. Dohlus, I. Zagorodnov
DESY, Hamburg, Germany

We describe the OCELOT open source project focusing on new beam dynamics simulation capabilities of the whole machine in modern electron-based x-ray sources. Numerical approaches for particle tracking and field calculations are discussed. In developing of the full-dimensional numerical modeling we pursue two important competitive aspects: the simulation has to be fast and has to include accurate estimations of collective effects. The simulation results for the European XFEL [1] are presented. The results have been benchmarked agains other codes and some of such benchmarks are shown.

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WEPAB033

Experimental Optimization and Characterization of Electron Beams for Generating IR/THz SASE FEL Radiation with PITZ

emittance, electron, FEL, radiation

2650

P. Boonpornprasert, Y. Chen, J.D. Good, H. Huck, I.I. Isaev, D.K. Kalantaryan, M. Krasilnikov, X. Li, O. Lishilin, G. Loisch, D. Melkumyan, A. Oppelt, H.J. Qian, Y. Renier, T. Rublack, F. Stephan
DESY Zeuthen, Zeuthen, Germany
G. Asova
INRNE, Sofia, Bulgaria
C. Saisa-ard
Chiang Mai University, Chiang Mai, Thailand
Q.T. Zhao
IMP/CAS, Lanzhou, People's Republic of China

The Photo Injector Test facility at DESY, Zeuthen site (PITZ), develops high brightness electron sources for modern linac-based Free Electron Lasers (FELs). The PITZ accelerator can also be considered as a suitable machine for the development of an IR/THz source prototype for pump-probe experiments at the European XFEL. One of the interesting options for the IR/THz generation with PITZ is to generate the radiation by means of a SASE FEL using an uncompressed electron beam with bunch length of a few 10 ps and a peak current of ~200 A. In this paper, results of experimental optimizations and characterizations, including transverse phase space, slice transverse emittance and longitudinal phase space, of electron beams with bunch charges of 4 nC are presented and discussed. The measurements were done with beam momenta of 15 MeV/c and 22 MeV/c. Results of IR/THz SASE FEL calculations by using the GENESIS1.3 code based on the measured beam parameters are also presented and discussed.

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WEPAB034

Control of Seeded FEL Pulse Duration Using Laser Heater Pulse Shaping

laser, electron, FEL, experiment

2654

V. Grattoni
Università degli Studi di Trieste, Trieste, Italy
E. Allaria, L. Badano, M.B. Danailov, A.A. Demidovich, S. Di Mitri, L. Giannessi, G. Penco, E. Roussel, P. Sigalotti, S. Spampinati, M. Trovò, M. Veronese
Elettra-Sincrotrone Trieste S.C.p.A., Basovizza, Italy
E. Ferrari
PSI, Villigen PSI, Switzerland

New Free-Electron Laser facilities deliver VUV and X-ray radiation with pulse length in the range of hundreds and tens of fs. A further reduction of the FEL pulse length is desired by those experiments aiming at probing ultrafast phenomena. Unlike SASE FEL, where the pulse duration is mainly driven by the electron bunch duration, in a seeded FEL the pulse duration can be determined by the seed laser properties. The use of techniques able to locally deteriorate the electron beam properties such as emittance or energy spread have been used in SASE FELs to reduce the region of the electron beam that is able to produce FEL radiation and hence reduce the FEL pulse length. The temporal shaping of the laser heater can be used to create an electron beam characterized by a very large energy spread all along the bunch except for a small region. We report measurements of the effect of the laser heater shaping on the electron beam phase-space performed at FERMI. Impact on the final FEL pulse properties are predicted with a series of numerical simulations.

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WEPAB070

Study of ESASE Scheme with Microbunching Instability for Generating Attosecond-Terawatt X-Ray Pulse in XFELs

laser, electron, FEL, free-electron-laser

2741

C.H. Shim, D.E. Kim, I.S. Ko
POSTECH, Pohang, Kyungbuk, Republic of Korea
Y.W. Parc
PAL, Pohang, Kyungbuk, Republic of Korea

Recent studies show that the attosecond-terawatt X-ray pulse in XFELs can be generated by using ESASE (enhanced self-amplified spontaneous emission) scheme to obtain a sub-femtosecond spike in the electron peak current. However, ESASE scheme is not working properly when the microbunching instability is taken into account. The instability can be suppressed when the laser heater system which increases the uncorrelated energy spread of the electron beam is used in the injector. The effect of the microbunching instability on the performance of ESASE scheme will be discussed. In addition, the optimized results with the laser heater system for generating attosecond-terawatt X-ray pulse in XFELs is also presented.

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WEPAB074

On the Coherence Properties of FEL

FEL, laser, undulator, experiment

2753

M.A. Pop, F. Curbis, S. Werin
MAX IV Laboratory, Lund University, Lund, Sweden

Free Electron Lasers (FEL) are one of the most brilliant light sources in the world and their unique properties are driving worldwide research in understanding and improving them. Numerous papers have already been published describing the output of the FEL in terms of coherence and bandwidth. In this contribution, however, we focus on how the coherence evolves along the FEL undulator and on what factors influence it the most. Using Genesis⁻¹.3* we have been able to follow and record the light field as it is being produced in the undulator. Our analysis method takes advantage of the extensively studied double pinhole experiment and uses the principles behind it to create a tool for extracting coherence information from the radiation field. We will present the scope, limitations and advantages of these virtual experiments as well as an application on an example FEL, to showcase what kind of information can be extracted using this method.
* Numerical simulation code used for particle and field distribution tracking along the undulator developed by Sven Reiche

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WEPAB084

Development of Injector System for MIR/THz Free-Electron Laser Facility in Thailand

electron, gun, undulator, FEL

2767

W. Thongpakdi, S. Rimjaem
Chiang Mai University, Chiang Mai, Thailand

Development of a linac-based MIR/THz FEL light source is ongoing at the Plasma and Beam Physics Research Facility, Chiang Mai University. The future facility will consist of an S-band thermionic cathode RF electron gun, a pre-magnetic bunch compressor in a form of alpha magnet, an S-band travelling-wave linac structure, a 180-degree achromat system and two undulator magnets equipped with optical cavities. This research focuses on start-to-end beam dynamics simulations of the injector system. The aim of the study is to produce high quality electron beam at the entrance of the THz undulator magnet. The simulation was conducted by using programs PARMELA and ELEGANT. The program PARMELA was utilized to study the electron beam dynamics inside the RF-gun. Then, the program ELEGANT was used to optimize the injector system parameters. Optimization of physical specifications for the achromat system was performed to obtain short electron bunches with small energy spread at the undulator entrance. In this paper, results of beam dynamics simulations with suitable condition for the THz-FEL beamline are presented and discussed.

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WEPAB088

Dark Current Studies in the CLARA Front-End Injector

gun, solenoid, linac, electron

2779

F. Jackson, I.R. Gessey, J.W. McKenzie, B.L. Militsyn, P.J. Tipping
STFC/DL/ASTeC, Daresbury, Warrington, Cheshire, United Kingdom

At STFC Daresbury a new facility CLARA (Compact Linear Accelerator for Research and Applications) is being designed and constructed. The principal aim of CLARA is advanced Free Electron Laser research. Halo and dark current in CLARA is a concern for damage to the undulator, and other applications of the machine. Recently the front end (gun, diagnostics, first linac) of CLARA has been installed including some collimation to mitigate halo effects. Beam halo may arise from gun field emission or due to beam dynamics in the early stages of acceleration, which may achieve the same energy as the core beam and thus may be transported to the undulator. The code CST is used to study the gun field emission. The code ASTRA is used to study the transport of field emission through the front end, including the effectiveness of collimators. Machine measurements of dark current are compared against these simulations.

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WEPAB089

Design Study for the Generation of Few-Cycle FEL Pulses Using Mode-Locked Afterburner Scheme at Clara

FEL, bunching, laser, radiation

2783

C.L. Shurvinton, D.J. Dunning, N. Thompson
STFC/DL/ASTeC, Daresbury, Warrington, Cheshire, United Kingdom

Ultrashort pulse operation in FELs is a highly desirable capability for imaging matter on ultrafast timescales. This paper presents a design study for a proof-Âof-Âprinciple demonstration of the mode-locked afterburner (ML-AB) scheme on the FEL test facility CLARA. A start-to-end simulation has been constructed using the time-Âdependent three-Âdimensional FEL code GENESIS 1.3 to evaluate the performance of the scheme. The ability to produce pulses of several femtoseconds in duration with peak powers of the order of 100 MW at 100 nm wavelength is predicted.Â Such pulses have duration of 2 fs (6 optical cycles), a factor of ~5 shorter than the FEL cooperation length. Potential routes for further optimisation and alternative operating modes are explored.

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WEPAB090

Developments in the CLARA FEL Test Facility Accelerator Design and Simulations

FEL, laser, undulator, optics

2787

P.H. Williams, D.J. Dunning, N. Thompson
STFC/DL/ASTeC, Daresbury, Warrington, Cheshire, United Kingdom

We present recent developments in the accelerator design of CLARA (Compact Linear Accelerator for Research and Applications), the proposed UK FEL test facility at Daresbury Laboratory. The requirement to co-propagate the beam with laser seeds of very different wavelengths has led to a redesign of the section preceding the undulators, with a dogleg being replaced by a chicane. Additional refinements of the facility design include the inter-undulator sections. With this finalised design we show start to FEL simulations for all beam modes envisaged.

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WEPAB097

Modelling Two-Colour FEL with Wide Wavelength Separation and Individual Polarisation Tuning

polarization, FEL, undulator, electron

2808

D. Bultrini, N. Thompson
Cockcroft Institute, Warrington, Cheshire, United Kingdom
R.J. Allan
The Hartree Centre, Science and Technology Facilities Council (STFC/DL), Warrington, United Kingdom
L.T. Campbell, B.W.J. MᶜNeil
USTRAT/SUPA, Glasgow, United Kingdom
D.J. Dunning, N. Thompson
STFC/DL/ASTeC, Daresbury, Warrington, Cheshire, United Kingdom
J.D.A. Smith
TXUK, Warrington, United Kingdom

Free electron lasers (FELs) are currently enabling cutting edge research in chemistry, biology and physics. We use simulations to assess a new FEL capability that would add to the impressive repertoire of experiments made possible by the technology: a two-colour independent polarization mode, which allows for light pulses with variable temporal separation, individually tuneable polarisation, and widely separated wavelength. Simulations are carried out using the broad bandwidth FEL code Puffin, the results of which are used to discuss the radiation properties of the output. This scheme is applicable to existing and proposed facilities which feature undulators with variable ellipticity and gap.

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WEPAB109

Multipole Field Effects in a Transverse Gradient Undulator

undulator, multipole, FEL, electron

2833

P. Baxevanis, Z. Huang
SLAC, Menlo Park, California, USA

Using a transverse gradient undulator (TGU) is one of the methods proposed in order to enable the utilization of electron beams with large energy spread (such as those from plasma-based accelerators) in a free-electron laser (FEL). Most of the analytical treatments of this scheme assume a linear variation of the undulator field with one of the transverse coordinates. While this assumption leads to a simplified and more tractable model, including higher-order multipoles allows us to offer a more complete and rigorous description of the system. In this paper, we investigate the magnetic field components of a TGU using both theory and simulation and explore the impact of higher-order multipoles on the FEL performance.

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WEPAB118

High Power Sub-Femtosecond X-Ray Pulse Study for the LCLS

undulator, electron, space-charge, photon

2848

J.P. MacArthur
Stanford University, Stanford, California, USA
J.P. Duris, Z. Huang, A. Marinelli
SLAC, Menlo Park, California, USA

The desire to resolve sub-femtosecond electron dynamics has pushed FEL facilities to shorter pulse lengths. However, current short-pulse schemes provide low pulse energy and a gain-length limited lower bound on the pulse duration. The X-ray Laser-Enhanced Attosecond Pulses (XLEAP) project at SLAC is designed implement an Enhanced Self Amplified Spontaneous Emission (ESASE) scheme, which produces sub-fs current spikes by modulating and compressing the electron beam. We show through a series of Genesis simulations that the current spike is capable of producing sub-fs pulses with a peak power well above 100 GW. Space-charge induced beam chirp can decrease pulse lengths below 400 as, and multi-stage schemes can increase peak x-ray powers to around 1 TW.

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WEPAB130

First Results from MICE Step IV

emittance, scattering, detector, solenoid

2878

P. Franchini
University of Warwick, Coventry, United Kingdom

Funding: STFC, DOE, NSF, INFN, CHIPP and more
Muon beams of low emittance provide the basis for the intense, well characterised neutrino beams of the Neutrino Factory and for lepton-antilepton collisions at energies of up to several TeV at a Muon Collider. The international Muon Ionization Cooling Experiment (MICE) will demonstrate ionization cooling - the technique by which it is proposed to reduce the phase-space volume occupied by the muon beam. MICE is being constructed in a series of Steps. The configuration currently in operation at the Rutherford Appleton Laboratory is optimised for the study the properties of liquid hydrogen and lithium hydride that affect cooling. The data taken in the present configuration have been partially analyzed and the available results will be described in detail.
submitted by the Speakers Bureau of the collaboration, in charge of
finding later a member to prepare and present the contribution

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WEPAB134

Progress on Beam-Plasma Effect Simulations in Muon Ionization Cooling Lattices

plasma, emittance, scattering, electron

2891

J.S. Ellison
IIT, Chicago, Illinois, USA
P. Snopok
Fermilab, Batavia, Illinois, USA
P. Snopok
Illinois Institute of Technology, Chicago, Illinois, USA

Funding: Work supported by the U.S. Department of Energy.
New computational tools are essential for accurate modeling and simulation of the next generation of muon-based accelerators. One of the crucial physics processes specific to muon accelerators that has not yet been simulated in detail is beam-induced plasma effect in liquid, solid, and gaseous absorbers. We report here on the progress of developing the required simulation tools and applying them to study the properties of plasma and its effects on the beam in muon ionization cooling channels.

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WEPIK001

Advanced Beam Dump for FCC-ee

collider, electron, distributed, positron

2906

A. Apyan
ANSL, Yerevan, Armenia
B. Goddard, F. Zimmermann
CERN, Geneva, Switzerland
K. Oide
KEK, Ibaraki, Japan

A modified beam dump for the future electron positron circular collider FCC-ee is discussed. The extraction line with a dilution kicker system distributes bunches at different transverse locations on the face of the beam dump. For a standard absorber the maximum energy deposition of all bunches occurs at the same longitudinal position inside the beam dump. This region experiences an enormous temperature rise compared with the surrounding parts of the beam dump. We propose a novel type of beam dump which spreads out the deposited energy over its whole volume quasi-uniformly, thereby reducing the maximum temperature rise. Results of Monte-Carlo simulations for a multi-material mosaic beam dump and for absorbers with distorted shapes are shown.

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WEPIK047

Frequency Choice Studies of eRHIC Crab Cavity

luminosity, cavity, ion, electron

3028

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

Funding: Work supported by Brookhaven Science Associates, LLC under Contract No. DE-AC02-98CH10886 with the U.S. Department of Energy.
Crab crossing scheme is essential collision scheme to achieve high luminosity for the future electron-ion collider (EIC). Since the ion beam is long when cooling is not present, the nonlinear dependence of the crabbing kick may present a challenge to the beam dynamics of the ion beam, hence a impact to the luminosity lifetime. In this paper, we present the initial result of the weak-strong and strong-strong beam-beam tracking with the crab crossing scheme. The result provides beam dynamics guidance in choosing the proper frequency the crab cavity for the future EIC.

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WEPIK055

Analysis and Countermeasures of Wakefield Heat Losses for Sirius

HOM, impedance, vacuum, storage-ring

3052

H.O.C. Duarte, L. Liu, S.R. Marques, T.M. da Rocha, F.H. de Sá
LNLS, Campinas, Brazil

Design evaluation and possible solutions for several in-vacuum components of Sirius are presented, having their impedance analysis focused on mitigating the wake heating impact. Thermal and/or structural simulation of the models are carried out by considering the heat load directly obtained from wakefield simulations with resistive wall boundary conditions.

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WEPIK057

Transverse Resonance Island Buckets as Bunch Separation Scheme

injection, optics, sextupole, operation

3059

P. Goslawski, A. Jankowiak, F. Kramer, M. Ries, M. Ruprecht, G. Wüstefeld
HZB, Berlin, Germany

Funding: Supported by the BMBF
Beam storage close to a tune resonance (Qx = 1/3,1/4) can generate transverse resonance island buckets in the x,x' phase space providing a second stable island orbit winding around the standard orbit. The two orbits are well separated, with good life time and stability. Successful user experiments have been conducted at BESSY II and the Metrology Light Source (MLS) *,** with such an operation mode. We discuss the required beam optics setup, the TopUp injection process and present successful measurements taken at photon beamlines at BESSY II.
* THPMR017, P.Goslawski et al., IPAC2016, Busan, Korea
** MOPWA021, M.Ries et al., IPAC2015, Richmond, USA

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WEPIK058

Preliminary Longitudinal Impedance Model for the ESRF-EBS

impedance, vacuum, undulator, storage-ring

3063

S.M. White
ESRF, Grenoble, France

In light sources, longitudinal beam coupling impedance can deteriorate performance through bunch lengthening or increased longitudinal emittance due to the microwave instability. Simulation estimates are therefore required to devise the appropriate counter-measures if necessary. The main contributors to the longitudinal impedance model of the new ESRF-EBS storage ring were simulated. A preliminary longitudinal impedance model is presented and preliminary tracking simulations are shown.

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WEPIK064

Eigenvalue Calculations Based on the Finite Element Method With Physically Motivated Field Smoothing Using the Kirchhoff Integral

cavity, electromagnetic-fields, extraction, radio-frequency

3074

W. Ackermann, H. De Gersem, T. Weiland
TEMF, TU Darmstadt, Darmstadt, Germany

In current linear particle accelerators, the actual acceleration of the charged particles is realized with the help of the electric field strength within driven radio frequency resonators. The characterization and optimization of the applied resonating structures can be reliably performed based on numerical simulation techniques. Efficient numerical methods have been introduced in the last decades to determine the electromagnetic fields while special care has been put in the correct description of the geometry and the material distribution of the structures. Although the resonators are operated in a driven setup, one of the advantageous numerical strategies here is given by an eigendecomposition of the fields which is realized by the application of accurate eigenmode calculations together with suitable postprocessing steps. In particular, the extraction of representative field maps used for particle tracking for example requires an accurate numerical modeling of the field at any position inside the structure. In order to avoid numerically motivated discontinuities of the fields a proper smoothing algorithm based on the vector equivalents of the Kirchhoff integral is proposed.

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WEPIK067

Beam-Dynamics Simulation Studies for the HESR

dynamic-aperture, dipole, multipole, coupling

3084

J.H. Hetzel, U. Bechstedt, J. Böker, A. Lehrach, B. Lorentz, S. Quilitzsch, H. Soltner, R. Tölle
FZJ, Jülich, Germany
A. Lehrach
RWTH, Aachen, Germany

The High Energy Storage Ring (HESR) is part of the future Facility for Antiproton and Ion Research (FAIR) placed in Darmstadt (Germany). The HESR is designed for antiprotons with a momentum range from 1.5 GeV/c to 15 GeV/c, but will as well be suitable to provide heavy ion beams with a momentum range from approximately 0.6 GeV/c to 5.8 GeV/c. To guarantee smooth operation it is crucial to verify and to optimize the design with beam-dynamics simulations. Within recent studies* calculations based on a variant of the Lyapunov exponent were carried out to estimate the dynamic aperture. The studies could reproduce expected influences as reduced aperture due to tune resonances and tune shifts due to coupling. Thus they can be extended to investigate the dynamic behaviour of the beam and identify the main restrictions to the dynamic aperture near the chosen betatron tune. Furthermore ongoing measurements of the magnetic fields of the already produced bending dipoles and quadrupoles deliver a more precise insight to the harmonic content of these elements. Thus the existing simulations could now be updated by including the new measurement results.
*J. Hetzel, A. Lehrach, U. Bechstedt, J. Böker, B. Lorentz, R. Tölle: Towards Beam-Dynamics Simulations Including More Realistic Field Descriptions for the HESR, IPAC'16

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WEPIK075

Electron Cloud Instability in SuperKEKB Phase I Commissioning

electron, target, permanent-magnet, solenoid

3104

K. Ohmi, J.W. Flanagan, H. Fukuma, H. Ikeda, E. Mulyani, K. Shibata, Y. Suetsugu, M. Tobiyama
KEK, Ibaraki, Japan

Beam size blow-up due to electron cloud has been observed in Phase I commissioning of SuperKEKB. Vacuum chambers in LER (low energy positron ring) were cured by antechamber and TiN coating for electron cloud. Some parts, bellows, were not cured by the coating. In the early stage of Phase I commissioning, beam size blow up has been observed above a threshold current. The blow up was suppressed by weak permanent magnets generating longitudinal field, which cover the bellows. Electron cloud current have been monitored during the commissioning. The thresholds for the electron cloud induced fast head-tail instability have been simulated in the operating beam conditions. Coupled bunch instability caused by electron cloud has been measured in the operating beam conditions and installation of the permanent magnets. The measurement and simulation results are presented.

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WEPIK077

Shielding of Beam Pipe on Rapidly Varying Magnetic Field

vacuum, shielding, feedback, emittance

3107

N. Wang, J. Chen, S.K. Chen, P. He, G. Xu
IHEP, Beijing, People's Republic of China

In low emittance rings, beam is quite sensitive to orbit oscillations. Fast correctors will be used to correct the beam orbit. The fast varying magnetic field will generate eddy current on the beam pipe, which will in turn change the phase and the amplitude of the magnetic field. The shielding effect of the beam pipe on a fast varying magnetic field is simulated for different frequencies. The results are also benchmarked with the measurements in the lab.

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WEPIK080

Preliminary Study of Beam Dynamics Compensation for the Elliptically Polarized Undulator at the HLS-II

electron, software, undulator, dynamic-aperture

3114

Z.H. Yang, Z.H. Bai, W. Li, L. Wang
USTC/NSRL, Hefei, Anhui, People's Republic of China

An elliptically polarized undulator (EPU) was installed at the upgraded Hefei Light Source, HLS-II, for special users. Due to that the area of good field of the EPU is not large enough, the resulting beam dynamics is serious. At present, the lattice is changed to lower beta functions at the EPU to solve this problem. However, the compensation for the EPU is necessary for better operation of the machine in the future. In this paper, we used the surface fitting method to extract the Hamiltonian of the EPU from the real surface magnetic field data. Thus, we can obtain the effective Hamiltonian of the ring, which can be analyzed using normal form or other techniques. Then the beam dynamics effects resulting from the EPU can be compensated by optimizing the nonlinear quantities with striplines.

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WEPIK084

Approximating Nonlinear Forces with Phase-Space Decoupling

octupole, proton, linac, sextupole

3120

B.T. Folsom, E. Laface
ESS, Lund, Sweden

Beam tracking software for accelerators typically falls into two categories: fast envelope simulations limited to linear beam optics, and slower multiparticle simulations that can model nonlinear effects. To find a middle ground between these approaches, we introduce virtual coordinates in position and momentum which have a cross-dependency (i.e. p*=f(x) where x is an initial position and p* is a virtual projection of momentum onto the position axis).This technique approximates multiparticle simulations with a significant reduction in calculation cost.

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WEPIK087

Measurement and Characterization of Cable Losses for High Voltage Coaxial Cables Used in Kicker Systems

impedance, kicker, network, injection

3131

A. Ferrero Colomo, L. Ducimetière, T. Kramer, L. Sermeus
CERN, Geneva, Switzerland

In the framework of CERN's LHC Injector Upgrade, simulation models for kicker pulse generators have been improved. A key element in the conventional pulse generators, among many others, are the high voltage coaxial cables. Since they can have significant impact on the waveform characteristics, an accurate cable model for simulation is crucial for reliable results during development. For this purpose, precise measurements of scatter parameters have been carried out in order to improve existing simulation models. Specialized high voltage cables, sometimes SF6 gas filled, used in various CERN kicker systems are usually large, heavy, not very flexible and often only one end is easy accessible. In addition, the impedance of these cables is rarely of 50 Ohms, which presents an extra difficulty. This paper describes the methods that have been defined and used to measure any kind of coaxial structures relying on S11 parameters exclusively. Measurements for various specialized cable types are presented and compared with their improved models. The implications for overall kicker system performance are briefly discussed.

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WEPIK089

Characterization of Resonant Impedances of CERN-SPS Gate Valves

impedance, resonance, coupling, vacuum

3139

T. Kaltenbacher, J. Repond, C. Vollinger
CERN, Geneva, Switzerland

For the CERN High Luminosity LHC project, a doubling of bunch intensity is foreseen. However, this intensity increase is currently limited by the LHC injector chain, in part due to longitudinal multi-bunch instabilities in the SPS. Therefore, the implementation of an accurate SPS impedance model was started some time ago in order to obtain a better understanding of instability sources and develop mitigation measures. In this paper, we present the electromagnetic characterization of commonly used all-metal gate valves with respect to their contribution to the SPS longitudinal impedance. The valve impedance was evaluated with commercially available EM-field simulation programs and verified with RF-bench measurements. Using this input, it was possible to obtain in particle simulations the dependence of the multi-bunch stability threshold on the number of these valves. A practical means of mitigation is to use a commercially available impedance shielded version of these gate valves. We also present the associated reduction in beam coupling impedance and the expected gain in beam stability if all existing unshielded valves are replaced by shielded valves.

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WEPIK091

Amplitude Dependent Closest Tune Approach Generated by Normal and Skew Octupoles

octupole, coupling, resonance, injection

3147

E.H. Maclean, T. Persson, R. Tomás
CERN, Geneva, Switzerland

Amplitude dependent closest tune approach, an action dependent analogue of the DQmin generated by linear coupling, was observed in the LHC during Run1. It restricts the accessible resonance free area of the tune diagram and by altering tune spread has the potential to impact upon Landau damping. A theoretical description of such behaviour, generated by normal octupoles and linear coupling has recently been validated in the LHC, however simulation has established that amp-dependent closest approach may also be generated by a combination of normal and skew octupoles. This paper summarizes these simulation based observations.

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WEPIK092

Effect of Linear Coupling on Nonlinear Observables at the LHC

coupling, dynamic-aperture, injection, octupole

3151

E.H. Maclean, F.S. Carlier, M. Giovannozzi, T. Persson, R. Tomás
CERN, Geneva, Switzerland

Simulation work during LHC Run 1 established that linear coupling had a large impact on nonlinear observables such amplitude detuning and dynamic aperture. It is generally taken to be the largest single source of uncertainty in the modelling of the LHC's nonlinear single particle dynamics. Measurements in 2016 sought to confirm this impact of linear coupling with beam. This paper summarizes the observed influence of linear coupling on various nonlinear observables in the LHC.

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WEPIK095

Evaluation of Longitudinal Beam Impedance in the Beam Gas Ionization Monitor of the CERN-PS Accelerator

impedance, coupling, wakefield, detector

3163

N. Nasr Esfahani, T. Kaltenbacher, J.W. Storey, C. Vollinger
CERN, Geneva, Switzerland

The recently observed beam induced heating issues in the BGI monitors of the LHC which could have been occurred due to a strong coupling between the beam and the localized modes at the sensor location showed the general importance of a thorough evaluation of the beam coupling impedance and the corresponding heat deposit in beam monitoring equipments. This paper is devoted to the examination of the beam coupling impedance and beam induced heating for a currently under development beam gas ionization (BGI) monitor which is intended to be a part of the CERN Proton Synchrotron (PS) beam monitoring equipment. Details of the EM and wake field simulations for this BGI monitor together with the RF measurement results and power loss calculations will be presented.

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WEPIK096

Assessment of Beam Impedance for the CERN-PS Booster Wire Scanner

coupling, impedance, booster, proton

3167

T. Kaltenbacher, N. Nasr Esfahani, C. Vollinger
CERN, Geneva, Switzerland

It is well known that performance of accelerators critically depends on the interaction of high intensity beams with the surrounding structures. As a result of these beam interactions, it is required at CERN to characterize the beam coupling impedance of each new machine element that is to be installed in the accelerator ring. In the framework of the LIU (LHC Injectors Upgrade) project, a new design of rotational wire scanner to be used in the PS Booster is currently under development. As an intermediate step, the prototype of this wire scanner was evaluated with respect to its longitudinal beam coupling impedance. Depending on the performance of this machine element, it is planned to replace existing wire scanners in other machines at CERN (e.g. PS-Booster, PS and SPS) with very similar designs. This paper presents the simulations and describes the measurement methods used for benchmarking electromagnetic simulations performed for the impedance evaluation of the LIU wire scanner for the PS-Booster. Additionally, the device was fitted with an RF feed-through in order to monitor and attenuate certain undesired modes supported by this structure.

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WEPIK099

Beam Lifetime Studies for SPS Storage Ring

storage-ring, insertion-device, operation, insertion

3178

P. Sudmuang, N. Juntong, P. Klysubun, T. Pulampong, N. Suradet
SLRI, Nakhon Ratchasima, Thailand

Limitation of beam lifetime was systematically investigated and studied for Siam Photon Source (SPS) storage ring. The objective was to identify the main cause of the observed reduction of beam lifetime. The simulations of momentum acceptance and Touschek lifetime were performed, incorporating non-linear effects generated by the installed high-field insertion devices. The Touschek lifetime was measured as a function of RF voltage and compared with the values obtained from simulation. The measurements were performed for a variety of different operation conditions of the insertion devices and different chromaticities.

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WEPIK106

Impedance and Collective Effects for the Advanced Light Source Upgrade at LBNL

impedance, wakefield, cavity, vacuum

3192

S. Persichelli, J.M. Byrd, S. De Santis, D. Li, T.H. Luo, C. Steier, M. Venturini
LBNL, Berkeley, California, USA

Funding: Work supported by the Director, Office of Science, of the U.S. Department of Energy under Contract No. DE-AC02-05CH11231
The upgrade of the Advanced Light Source (ALS-U) consists of a multiband achromat ultralow emittance lattice for the production of diffraction-limited soft x-rays. A very important issue for ALS-U is represented by instabilities induced by wakefields, that may limit the peak current of individual bunches and the total beam current. In addition, vacuum chamber apertures of few millimeters, that are a key feature of low-emittance machines, can result in a significant increase in the Resistive Wall (RW) impedance. In this paper we present progress on establishing short range wakefield model for ALS-U and evaluating the impact on the longitudinal and transverse single-bunch dynamics.

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WEPIK109

Experimental Study of Vertical-Longitudinal Coupling Induced by Wakefields at CesrTA

wakefield, lattice, coupling, electron

3200

S. Wang, J.D. Perrin, S. Poprocki, D. L. Rubin
Cornell University (CLASSE), Cornell Laboratory for Accelerator-Based Sciences and Education, Ithaca, New York, USA

Funding: Work supported by NSF PHY-1416318, PHYS-1068662
Transverse vertical wakefields can cause vertical beam size growth in accelerators. Here we report recent measurements and simulations of wakefields from movable scrapers at the CesrTA. The charge dependent vertical beam size growth was observed while a single scraper was inserted through the top of the chamber. No change in the beam size was observed with top and bottom scrapers inserted symmetrically. The apparent growth in the vertical beam size was due in large part to the y-z coupling (vertical crabbing) induced by the monopole wake of the asymmetric scraper configuration. We explored this y-z coupling by varying vertical betatron phase advance between the vertical beam size monitor and the scrapers. In addition, we found that existing residual, current independent y-z coupling could be compensated by the scraper wake. Predictions of a tracking simulation are in good agreement with the measurements.

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WEPIK110

Resistive Wall Instability and Impedance Studies of Narrow Undulator Chamber in CHESS-U

undulator, lattice, wakefield, dipole

3204

S. Wang, M.G. Billing, S. Poprocki, D. L. Rubin, D. Sagan
Cornell University (CLASSE), Cornell Laboratory for Accelerator-Based Sciences and Education, Ithaca, New York, USA

Funding: Work supported by NSF DMR-0936384 and NSF DMR-1332208
In a major upgrade of the Cornell Electron Storage Ring (CESR) one sextant of ring will be replaced with double bend achromats (DBAs) and undulator straights for x-ray users. The resistive wall impedance from the narrow gap (4.5 mm) undulator chambers (5 m per straight) may limit total beam. Here we report recent results of modelling and calculation of multibunch instabilities due to the impedance of chamber walls and transition tapers. The short range wakefields and resistive wall impedance are modelled and incorporated in a tracking simulation. The coupled-bunch growth rate found with the tracking study is in good agreement with the analytic approximation. We find that the resistive wall instability can be readily damped by our existing bunch-by-bunch feedback system.

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WEPIK112

A 2D Finite Element Solver for Electromagnetic Fields with m-fold Azimuthal Symmetry

operation, interface, gun, cavity

3211

A.R. Vrielink, M.H. Nasr, S.G. Tantawi
SLAC, Menlo Park, California, USA

Radiofrequency (RF) cavities for use in accelerators, from RF sources to accelerating and transverse cavities, often exhibit m-fold azimuthal symmetry. For cases where m>0, commercially available finite element codes used to simulate the beam-wave interaction typically require a full 3D simulation. We have derived a finite element formulation which accounts for the known azimuthal dependence of the electromagnetic fields, allowing us to solve for these problems on a 2D mesh and reducing simulation times significantly. The theory, including the construction of the local finite element matrices and the selection of appropriate basis functions, will be presented in addition to numerical results.

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WEPIK114

Study of Electron Polarization Dynamics in the JLEIC at JLab

polarization, electron, collider, synchrotron

3218

F. Lin, Y.S. Derbenev, V.S. Morozov, Y. Zhang
JLab, Newport News, Virginia, USA
D.P. Barber
DESY, Hamburg, Germany

Funding: Authored by Jefferson Science Associates, LLC under U.S. DOE Contract No. DE-AC05-06OR23177 and DE-AC02-06CH11357.
The design of an electron polarization scheme in the Jefferson Lab Electron-Ion Collider (JLEIC) aims to attain a high longitudinal electron polarization (over 70%) at collision points as required by the nuclear physics program. Comprehensive strategies for achieving this goal have been considered and developed including injection of highly polarized electrons from CEBAF, mechanisms for manipulation and preservation of the polarization in the JLEIC collider ring and measurement of the electron polarization. In particular, maintaining a sufficiently long polarization lifetime is crucial for accumulation of adequate experimental statistics. The chosen electron polarization configuration, based on the unique figure-8 geometry of the ring, removes the electron spin-tune energy dependence. This significantly simplifies the control of the electron polarization and suppresses the synchrotron sideband resonances. This paper reports recent studies and simulations of the electron polarization dynamics in the JLEIC electron collider ring.

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WEPIK116

Aberration Compensation in a Skew Parametric-Resonance Ionization Cooling Channel

multipole, resonance, damping, sextupole

3221

A.V. Sy, Y.S. Derbenev, V.S. Morozov
JLab, Newport News, Virginia, USA
A. Afanasev
GWU, Washington, USA
Y. Bao
UCR, Riverside, California, USA
R.P. Johnson
Muons, Inc, Illinois, USA

Funding: This work was supported in part by U.S. DOE STTR Grant DE-SC0005589. Authored by Jefferson Science Associates, LLC under U.S. DOE Contract No. DE-AC05-06OR23177.
Skew Parametric-resonance Ionization Cooling (Skew PIC) represents a novel method for focusing of highly divergent particle beams, as in the final 6D cooling stage of a high-luminosity muon collider. In the muon collider concept, the resultant equilibrium transverse emittances from cooling with Skew PIC are an order of magnitude smaller than in conventional ionization cooling. The concept makes use of coupling of the transverse dynamic behavior, and the linear dynamics are well-behaved with good agreement between analytic solutions and simulation results. Compared to the uncoupled system, coupling of the transverse dynamic behavior purports to reduce the number of multipoles required for aberration compensation while also avoiding unwanted resonances. Aberration compensation is more complicated in the coupled case, especially in the high-luminosity muon collider application where equilibrium angular spreads in the cooling channel are on the order of 200 mrad. We present recent progress on aberration compensation for control of highly divergent muon beams in the coupled correlated optics channel, and a simple cooling model to test the transverse acceptance of the channel.

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WEPIK117

A Comprehensive Study of the Microwave Instability

lattice, storage-ring, electron, vacuum

3224

A. Blednykh, B. Bacha, G. Bassi, O.V. Chubar, M.S. Rakitin, V.V. Smaluk, M. Zhernenkov
BNL, Upton, Long Island, New York, USA

Funding: Work supported by DOE contract DE-SC0012704
Several instability thresholds and special waveform beam pattern have been observed during measurements of the horizontal beam size change vs single bunch current by the synchrotron light monitor (SLM) camera installed in a low dispersion area of the NSLS-II storage ring. The electron beam energy spread from In-Vacuum Undulator (IVU) of the Soft Matter Interfaces (SMI) beam line confirmed the microwave beam pattern behavior as a current dependent effect. The numerically obtained total longitudinal wakepotential by the GdfidL code allowed us to compare the measured results with particle tracking simulations using the SPACE code. The instability thresholds behavior at different RF voltages are in some sort of overarching agreement.

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WEPIK121

Computation of Synchrotron Radiation on Arbitrary Geometries in 3D with Modern GPU, Multi-Core, and Grid Computing

GPU, undulator, radiation, brightness

3238

D.A. Hidas
BNL, Upton, Long Island, New York, USA

Funding: Supported by the U.S. Department of Energy under contract DE-SC0012704
Open Source Code for Advanced Radiation Simulation (OSCARS*) is an open source project being developed at Brookhaven National Laboratory for the computation of synchrotron radiation from arbitrary particle beams in arbitrary magnetic (and electric) fields on arbitrary geometries in 3D. OSCARS was designed with considerations for modern large scale computing infrastructure. These include the ability to use GPUs for computations, multi-threaded computations, and utilities for grid (or cloud) computing. Primary applications include, but are not limited to, the computation of spectra, photon flux densities, and notably, power density distributions on arbitrary geometries in 3D which is of interest in accelerator component study and design. This modern approach and several complex geometries will be highlighted and elaborated on.
* http://oscars.bnl.gov

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WEPVA001

Electron Injector for Multi-Stage Laser-Driven Plasma Accelerators

electron, laser, plasma, acceleration

3244

B. Cros, T. Audet, P. Lee, G. Maynard
CNRS LPGP Univ Paris Sud, Orsay, France
A. Chancé, O. Delferrière, A. Mosnier
CEA/DSM/IRFU, France
N. Delerue
LAL, Orsay, France
S. Dobosz-Dufrénoy, A. Maitrallain, P. Monot
CEA, Gif-sur-Yvette, France
J. Schwindling
CEA/IRFU, Gif-sur-Yvette, France
A. Specka
LLR, Palaiseau, France

Funding: LAbex PALM, Labex P2IO, Triangle de la Physique, ANR grant Equipex CILEX APOLLON, EU H2020 research and innovation programme under grant agreement No. 653782 EUPRAXIA.
An electron injector in the 50-200 MeV range, based on laser wakefield acceleration, is studied in the context of multi-stage laser plasma acceleration. Test experiments carried out at the UHI100 laser facility show that electron bunches in the 100 MeV range, generated by ionization-induced injection mechanism, and accelerated by laser driven wakefield in a mm-scale length plasma can be transported using a magnetic line and precisely analysed. A comparison with simulation results provides insights on electron dynamics and indicates ways to optimize the injector.

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WEPVA002

Simulations of DLA Grating Structures in the Frequency Domain

laser, electron, cavity, acceleration

3247

T. Egenolf, O. Boine-Frankenheim, U. Niedermayer
TEMF, TU Darmstadt, Darmstadt, Germany
O. Boine-Frankenheim
GSI, Darmstadt, Germany

Dielectric laser accelerators (DLA) driven by ultrashort laser pulses can reach orders of magnitude larger gradients than contemporary RF electron accelerators. A new implemented field solver based on the finite element method in the frequency domain allows the calculation of the structure constant, i.e. the ratio of energy gain to laser peak amplitude. We present the maximization of this ratio as a parameter study looking at a single grating period only. Based on this optimized shape the entire design of a beta-matched grating is completed in an iterative process. The period length of a beta-matched grating increases due to the increasing velocity of the electron when a subrelativistic beam is accelerated. The determination of the optimal length of each grating period thus requires the knowledge of the energy gain within all so far crossed periods. Furthermore, we outline to reverse the excitation in the presented solver for beam coupling impedance calculations and an estimation of the beam loading intensity limit.

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WEPVA004

Simulation of an Electromagnetic Field Excitation by a THz-pulse and Acceleration of an Electron Bunch in a Dielectric-loaded AXSIS Linac

linac, electron, acceleration, injection

3253

K. Galaydych, R.W. Aßmann, U. Dorda, B. Marchetti, G. Vashchenko, I. Zagorodnov
DESY, Hamburg, Germany

Funding: The research leading to these results has received funding from the European Research Council under the European Union's Seventh Framework Programme (FP/2007-2013) / ERC Grant Agreement n. 609920
The Attosecond X-ray Science: Imaging and Spectroscopy (AXSIS) experiment at DESY will use a dielectric loaded waveguide to accelerate electron bunches up to 15 MeV. Such a linac will be powered by a narrowband multicycle THz-pulse with a central frequency of 300 GHz. In this paper we focus on the reflection of the excited field at a pinhole, on the optimization of the bunch injection time and on the bunch dynamics in the acceleration process. The linac excitation by the THz-pulse and the bunch acceleration in the excited field are investigated using CST and ECHO simulations.

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WEPVA005

Simulation of a Many Period Dielectric Grating-based Electron Accelerator

laser, electron, emittance, acceleration

3256

W. Kuropka, R.W. Aßmann, U. Dorda, F. Mayet
DESY, Hamburg, Germany
W. Kuropka, F. Mayet
University of Hamburg, Institut für Experimentalphysik, Hamburg, Germany

Funding: GBMF - Gordon and Betty Moore Foundation
Dielectric laser driven particle accelerators have become a research area of major interest due to the high acceleration gradients achievable. Those are mainly attributed to the high damage thresholds of dielectrics at optical frequencies. Simulations of these structures are usually computed with Particle-In-Cell (PIC) codes. Their accuracy and self consistency comes with a major drawback of high computation costs. Computation of structures consistent of hundreds to thousands of periods are only viable with High Performance Computing clusters. In this proceeding a compromise of CST* PIC simulations combined with a transfer function model is presented to simulate relativistic electron accelerators for particle energies up to the GeV regime or higher. In addition a simplified example accelerator design is investigated and the required electron bunch parameters from a sub-relativistic source are computed.
*CST - Computer Simulation Technology, available from www.
cst.com.

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WEPVA006

A Concept for Phase-Synchronous Acceleration of Microbunch Trains in DLA Structures at SINBAD

laser, electron, acceleration, linac

3260

F. Mayet, R.W. Aßmann, J. Bödewadt, R. Brinkmann, U. Dorda, W. Kuropka, C. Lechner, B. Marchetti, J. Zhu
DESY, Hamburg, Germany
W. Kuropka, F. Mayet
University of Hamburg, Institut für Experimentalphysik, Hamburg, Germany
J. Zhu
University of Hamburg, Hamburg, Germany

Funding: GBMF - Gordon and Betty Moore Foundation
The concept of dielectric laser accelerators (DLA) has gained increasing attention in accelerator research, because of the high achievable acceleration gradients (~GeV/m). This is due to the high damage threshold of dielectrics at optical frequencies. In the context of the Accelerator on a Chip International Program (ACHIP) we plan to inject electron bunches into a laser-illuminated dielectric grating structure. At a laser wavelength of 2 micro-meter the accelerating bucket is <1.5 fs. This requires both ultra-short bunches and highly stable laser to electron phase. We propose a scheme with intrinsic laser to electron synchronization and describe a possible implementation at the SINBAD facility (DESY). Prior to injection, the electron bunch is conditioned by interaction with an external laser field in an undulator. This generates a sinusoidal energy modulation that is transformed into periodic microbunches in a subsequent chicane. The phase synchronization is achieved by driving both the modulation process and the DLA with the same laser pulse. This allows scanning the electron bunch to laser phase and will show the dependence of the acceleration process on this delay.

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WEPVA007

Simulations and Plans for a Dielectric Laser Acceleration Experiment at SINBAD

laser, experiment, electron, linac

3264

F. Mayet, R.W. Aßmann, U. Dorda, W. Kuropka, B. Marchetti, J. Zhu
DESY, Hamburg, Germany
W. Kuropka, F. Mayet
University of Hamburg, Institut für Experimentalphysik, Hamburg, Germany
J. Zhu
University of Hamburg, Hamburg, Germany

Funding: GBMF - Gordon and Betty Moore Foundation
In this work we present the outline of an experimental setup for dielectric laser acceleration of relativistic electron bunches produced by the ARES linac under construction at the SINBAD facility (DESY Hamburg). The experiment will be performed as part of the Accelerator on a Chip International Program (ACHIP), funded by the Gordon and Betty Moore Foundation. At SINBAD we plan to test the acceleration of already pre-accelerated relativistic electron bunches in a laser-illuminated dielectric grating structure. In addition to the conceptual layout of the experiment we present first start-to-end simulation results for different ARES working points. The simulations are performed using a combination of the well known particle tracking code ASTRA and the self-consistent particle in cell code VSim.

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WEPVA011

Development of a Laser Driven Dielectric Accelerator for Radiobiology Research

electron, laser, acceleration, experiment

3272

K. Koyama, M. Yoshida
KEK, Ibaraki, Japan
Z. Chen, H. Okamoto
The University of Tokyo, Tokyo, Japan
M. Uesaka
The University of Tokyo, Nuclear Professional School, Ibaraki-ken, Japan

Funding: This work was supported by KAKENHI, (Grant-in-Aid for Scientific Research) Grant Number 15H03595 and partly supported by NIMS Nanofabrication Platform in Nanotechnology Platform Project sponsored by the Ministry of Education, Culture, Sports, Science and Technology (MEXT), Japan.
A laser-driven dielectric accelerator below 1 MeV is under development for applying a sub-micron size electron-beam to radiobiological research. Simulations of the electric field and electron trajectories in the proximity of the dielectric structure (transmission grating) were performed in order to fix parameters of the demonstration experiment. Serious deflection of electron beam towards the grating limited the injection phase as well as the height from the structure. The energy gain of 50-keV electron was estimated to be 1 keV in 30-micron length at the optimum condition. Transmission gratings for the experiment were fabricated by using facilities of the NIMS Nanofabrication Platform. In addition to the acceleration experiment using the simple grating, a resonator type accelerator structure was designed for exciting the acceleration field by a moderately small laser.

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WEPVA014

Status of R&D on New Superconducting Injector Linac for Nuclotron-NICA

linac, proton, ion, injection

3282

G.V. Trubnikov, A.V. Butenko, N. Emelianov, A.O. Sidorin, E. Syresin
JINR, Dubna, Moscow Region, Russia
T.A. Bakhareva, M. Gusarova, T. Kulevoy, S.V. Matsievskiy, S.M. Polozov, A.V. Samoshin, N.P. Sobenin, D.V. Surkov, K.V. Taletskiy, S.E. Toporkov, V. Zvyagintsev
MEPhI, Moscow, Russia
A.A. Bakinowskaya, A.A. Marysheva, V.S. Petrakovsky, I.L. Pobol, A.I. Pokrovsky, D.A. Shparla, S.V. Yurevich, V.G. Zaleski
Physical-Technical Institute of the National Academy of Sciences of Belarus, Minsk, Belarus
M.A. Baturitski, S.A. Maksimenko
INP BSU, Minsk, Belarus
S.E. Demyanov
Scientific-Practical Materials Research Centre of the National Academy of Sciences of Belarus, Minsk, Belarus
V.A. Karpovich
BSU, Minsk, Belarus
T. Kulevoy, S.M. Polozov
ITEP, Moscow, Russia
A.A. Kurayev, V.V. Matbeenko, A.O. Rak
Belarus State University of Informatics and Radioelectronics (BSUIR), Minsk, Belarus
V.N. Rodionova
Belarussian State University, Scientific Research Institute of Nuclear Problems, Minsk, Belarus
A.O. Sidorin
Saint Petersburg State University, Saint Petersburg, Russia
V. Zvyagintsev
TRIUMF, Vancouver, Canada

The new collaboration of JINR, NRNU MEPhI, INP BSU, PTI NASB, BSUIR and SPMRC NASB starts in 2015 the project of linac-injector design in 2015. The goal of new linac is to accelerate protons up to 25 MeV (and up to 50 MeV at the second stage) and light ions to ~7.5 MeV/u for Nuclotron-NICA injection. Current results of the linac general design and development, beam dynamics simulations, SC cavities design and SRF technology development are presented in this report.

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WEPVA019

Group Velocity Matching in Dielectric-Lined Waveguides and its Role in Electron-THz Interaction

electron, acceleration, accelerating-gradient, interface

3296

A.L. Healy, G. Burt
Cockcroft Institute, Lancaster University, Lancaster, United Kingdom
D.M. Graham
The University of Manchester, The Photon Science Institute, Manchester, United Kingdom
S.P. Jamison
STFC/DL/ASTeC, Daresbury, Warrington, Cheshire, United Kingdom

Terahertz(THz)-driven dielectric-lined waveguides have applications in electron manipulation, particularly acceleration, as the use of dielectric allows for phase velocities below the speed of light. However matching a single frequency to the correct velocity does not maximise electron-THz interaction; waveguide dispersion typically results in an unmatched group velocity and so the pulse envelope of a short THz pulse changes along the length of the structure. This reduces field amplitude and therefore accelerating gradient as the envelope propagates at a different velocity to the electron. Presented here is an analysis of the effect of waveguide dispersion on THz-electron interaction and its influence on structure dimensions and choice of THz pulse generation. This effect on net acceleration is demonstrated via an example of a structure excited by a single-cycle THz pulse, with a comparison of multi-cycle, lower intensity THz pulses on net acceleration.

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WEPVA020

Dual-Grating Dielectric Accelerators Driven by A Pulse-Front-Tilted Laser

laser, electron, accelerating-gradient, vacuum

3299

Y. Wei, C.P. Welsch
The University of Liverpool, Liverpool, United Kingdom
M.M. Dehler, E. Ferrari, N. Hiller, R. Ischebeck
PSI, Villigen PSI, Switzerland
J.D.A. Smith
TXUK, Warrington, United Kingdom
C.P. Welsch
Cockcroft Institute, Warrington, Cheshire, United Kingdom
G.X. Xia
UMAN, Manchester, United Kingdom

Dual-grating Dielectric Laser-driven Accelerators (DLAs) are considered to be one of the most promising technologies to miniaturize future particle accelerators. Accelerating gradients in the GV/m range seem accessible and 690 MV/m has been demonstrated in fused silica structures. However, the increase in beam energy is limited by the short interaction length between the laser pulses and the electron bunch. In this contribution, a pulse-front-tilt operation for a laser beam is studied to extend the interaction length, resulting in a greater energy gain for a dual-grating DLA. The VSIM code is used to compare this new scheme with the commonly used approach of a normally incident laser beam and advantages are summarized.
[1]T. Plettner, et al., Phys. Rev. ST Accel. Beams 9, 111301 (2006)
[2]K. P. Wootton, et al., Opt. Lett., 41, 2696 (2016).
[3]E. A. Peralta, et al., Nature 503, 91 (2013)

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WEPVA021

Phase Space Manipulation of Sub-Picosecond Electron Bunches Using Dielectric Wakefield Structures

emittance, wakefield, FEL, electron

3302

T.H. Pacey, G.X. Xia
UMAN, Manchester, United Kingdom
D.J. Dunning, Y.M. Saveliev
STFC/DL/ASTeC, Daresbury, Warrington, Cheshire, United Kingdom

Dielectric lined waveguides have drawn interest due to their application as high gradient accelerating structures, in both externally driven and wakefield schemes. We present simulation studies of sub-picosecond electron bunches interacting with dielectric structures in the self-wake regime. The parameter space for a tunable, sub-millimeter aperture, terahertz frequency structure is investigated. The potential application as a longitudinal phase space dechirper is demonstrated, with specific application to CLARA at Daresbury Laboratory. The impact of transverse effects is considered and minimised. The resulting FEL output is simulated.

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WEPVA023

Performance of the PS Injection Kicker System Short Circuit Mode Upgrade for Operation with 2 GeV LIU Beams

flattop, kicker, injection, operation

3308

T. Kramer, W. Bartmann, J.C.C.M. Borburgh, L. Ducimetière, L.M.C. Feliciano, A. Ferrero Colomo, B. Goddard, L. Sermeus
CERN, Geneva, Switzerland

In the framework of the LHC Injector Upgrade (LIU) project an upgrade of the existing PS proton injection kicker system for 2 GeV operation is in progress. The upgrade is based on the operation of the existing kicker system in short circuit mode. This paper briefly reviews the deployed modifications to the system to obtain the specified reduction of pulse reflections unavoidably induced by such a configuration. The implementation of improvements to the magnet entry box, transmission cables and the short circuit plug with integrated LC-filter are described as well as tests and measurements during the 2016/17 annual shutdown. The impact of the residual pulse shape structure on the beam performance for the reference LIU beam is quantified. The paper concludes with a performance analysis, a comparison of measurements vs. simulations and an outlook to the remaining modifications during the next long shut down.

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WEPVA035

The PSB Operational Scenario with Longitudinal Painting Injection in the Post-LIU Era

injection, target, linac, controls

3331

V. Forte, S.C.P. Albright, M.E. Angoletta, P. Baudrenghien, E. Benedetto, A. Blas, C. Bracco, C. Carli, A. Findlay, R. Garoby, G. Hagmann, A.M. Lombardi, B. Mikulec, M.M. Paoluzzi, J.L. Sanchez Alvarez, R. Wegner
CERN, Geneva, Switzerland

Longitudinal painting has been presented as an elegant technique to fill the longitudinal phase space at injection to the CERN PSB once it is connected with the new Linac4. Painting brings several advantages related to a more controlled longitudinal filamentation, lower peak line density and beating reduction, resulting in a smaller space-charge tune spread. This could be an advantage especially for high intensity beams (> 6·10¹² protons per bunch) to limit losses on the transverse acceptance of the machine. This paper presents an overview on the possible advantages of the technique for operational and test beams, taking care of the hardware limitations and possible failure scenarios.

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WEPVA038

Tail Repopulation Measurements in the PSB

kicker, emittance, injection, experiment

3343

E. Benedetto, M. Cieslak-Kowalska, P. Zisopoulos
CERN, Geneva, Switzerland
M. Cieslak-Kowalska
EPFL, Lausanne, Switzerland

The PS Booster (PSB) is the first circular accelerator in the LHC injector chain providing protons for the full CERN complex. Each of its four rings provides beams in a range of intensities varying from 40 e11 p/cycle to 0.8 e13 p/cycle. Low intensity beams are produced by transverse shaving, that is by scraping the tails, in order to tailor the intensity and transverse emittances. Eventually, tails repopulate and the beam profile reshapes, under the effect of space charge, which is dominant at low energy in the PS Booster. This paper describes the results of the measurements after the shaving process, where the tails are scraped but finally re-appear in the transverse profile, and it provides a first benchmark with space-charge simulations. It highlights the challenges encountered and the lessons learned, to guide the future experiments. The final outcome of these studies is the characterisation of the halo creation mechanism and the determination of the diffusion speed, important for the design of the future PS Booster scraping system.

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WEPVA039

Transition Crossing in the Main Injector for PIP-II

lattice, booster, emittance, operation

3347

R. Ainsworth, S. Chaurize, I. Kourbanis, E.G. Stern
Fermilab, Batavia, Illinois, USA

Proton Improvement Plan-II (PIP-II) is Fermilab's plan for providing powerful, high-intensity proton beams to the laboratory's experiments. PIP II will include upgrades to the Booster, Recycler and Main Injector which will be required to accelerate 50% more beam as well as increasing the Booster repetition rate from 15 to 20 Hz. To accommodate the faster rate, the momentum separation of the slip stacking beams in the Recycler must increase which will result in in larger longitudinal emittance bunches in MI. In order to cross transition without losses, it is expected a gamma-t jump will be needed. Gamma-t jump schemes for the MI are investigated.

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WEPVA094

Study of an Improved Beam Screen Design for the LHC Injection Kicker Magnet for HL-LHC

impedance, kicker, injection, coupling

3471

V. Vlachodimitropoulos, M.J. Barnes, L. Ducimetière, L. Vega Cid, W.J.M. Weterings
CERN, Geneva, Switzerland

During Run 1 of the LHC, one of the injection kicker magnets (MKIs) occasionally exhibited an excessively high ferrite temperature, caused by coupling of the high intensity beam to the real impedance of the magnet. Beam-screen upgrades have been very effective in reducing beam coupling impedance during Run 2. However, temperature measurements during LHC operation have shown that one end of the MKIs ferrite yoke is consistently hotter than the other: this effect is due to highly non-uniform beam induced power deposition along the kicker. Electromagnetic and thermal simulations show that part of the ferrite yoke will be above its Curie temperature when the LHC is operated with HL-LHC beam parameters, which could increase the turn-around time between fills of the LHC. An impedance mitigation study is presented in this paper with emphasis on the effect of the beam screen layout upon both total beam induced power deposition and its longitudinal distribution. Results of complex thermal simulations, to benchmark the effectiveness of the proposed schemes, are reported. To validate the proposed modification a test bench measurement was performed and preliminary results are discussed

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WEPVA096

Thermal Analysis of the LHC Injection Kicker Magnets

injection, kicker, vacuum, operation

3479

L. Vega Cid, M.J. Barnes, V. Vlachodimitropoulos, W.J.M. Weterings
CERN, Geneva, Switzerland
A. Abánades
ETSII UPM, Madrid, Spain

Funding: Research supported by the HL-LHC project.
The CERN Large Hadron Collider LHC is equipped with two fast pulsed magnet systems (MKIs) that inject particle beams coming from the injector chain. Operation with high intensity beams for many hours can lead to significant beam induced heating of the ferrite yokes of the MKIs. When the ferrite exceeds the Curie temperature of 125°C it loses its magnetic properties, preventing further injection until the ferrite cools down, potentially causing a delay of several hours. Hence important upgrades of the beam-screen were implemented after Run 1 of LHC. However, the High-Luminosity (HL) LHC will be operated with significantly higher intensity beams and hence additional measures are required to limit the ferrite temperature. These magnets operate under ultra-high vacuum conditions: convection is negligible and, as a result of low emissivity of the inside of the vacuum tanks, thermal radiation is limited. A detailed study of the thermal behaviour of these magnets is reported and compared with measurements. In addition several options to improve cooling of the ferrites are presented and analysed.

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WEPVA101

Review of Stripline Beam Impedance: Application to the Extraction Kicker for the CLIC Damping Rings

impedance, coupling, kicker, extraction

3499

C. Belver-Aguilar, M.J. Barnes
CERN, Geneva, Switzerland

The beam coupling impedance of the stripline kicker for beam extraction from the CLIC Damping Rings (DRs) has been studied analytically, numerically with CST Particle Studio (PS) and measured in the laboratory, although not all the results were understood. In order to have a better knowledge about the beam coupling impedance of a stripline kicker, a simple model has been first studied, with flat electrodes and a cylindrical beam pipe. From this preliminary study, a new approach for the dipolar component of the horizontal impedance has been derived, when considering both odd and even operating modes of the striplines. This new approach has been used to understand the differences found between the predicted transverse impedance and the two wire measurements carried out in the laboratory for the prototype CLIC DR striplines. Future tests of beam coupling impedance with beam in the ALBA Synchrotron Ligth Source will complete this study.

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WEPVA103

Renovation of CERN Antiproton Production Target Area and Associated Design, Testing and R&D Activities

target, antiproton, operation, proton

3506

C. Torregrosa, M.E.J. Butcher, M. Calviani, A. De Macedo, S. De Man, R. Ferriere, E. Grenier-Boley, B. Lefort, E. Lopez Sola, A. Perillo-Marcone, M.A. Timmins
CERN, Geneva, Switzerland

In the Antiproton Decelerator (AD) Target Area antiprotons are produced by the collisions of 26 GeV/c proton beam with a fixed target. They are then collected by a 400 kA pulsed magnetic horn, momentum selected and injected into the AD facility. The area has been in operation since the 80s, keeping most of the equipment dating back to this period. A major upgrade is foreseen during the CERN's Long Shutdown 2 to guarantee the next decades of antiproton physics. Among other R&D activities, three main systems are within the scope of this upgrade; (i) a new antiproton target design, pressurized-air-cooled and with a new core configuration based on the results from the HiRadMat27 experiment. (ii) Manufacturing of a set of new magnetic horns and testing them using a dedicated test bench replicating the real horn setup. (iii) Design of new target and horn's trolleys, which are responsible for their positioning as well as providing an efficient long term maintenance giving the high radioactivity of the area. This paper presents an overview of these and other critical activities associated to the renovation of the target area, including status and direction of the new proposed designs.

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WEPVA109

Design of the New PS Internal Dumps, in the Framework of the LHC Injector Upgrade (LIU) Project

dumping, operation, injection, vacuum

3521

G. Romagnoli, J.A. Briz Monago, M. Calviani, J.J. Esala, E. Grenier-Boley, A. Masi, F.-X. Nuiry, A. Perillo-Marcone, T. Polzin, V. Vlachoudis
CERN, Geneva, Switzerland

For the LHC injectors upgrade (LIU) at CERN, the two PS (Proton Synchrotron) dumps will be redesigned and upgraded for the new high intensity beams. The EN-STI group is in charge of the design and installation of the new dumps, foreseen for the next CERN's Long Shutdown in 2019-2020. As internal dumps, the PS dumps have been installed in 1975 directly in the PS vacuum ring between the main bending magnets and they are operating since then. The dumps enter the beam line when requested by beam operation, with a 6 kg Cu block moved quickly with a spring-based mechanism. This Cu block is not expected to survive the impact of the future beams. A new design is presented for the dump core based on FLUKA-ANSYS coupled simulations. The dumps should work with any PS beam foreseen within LIU, be water cooled in ultra-high vacuum medium, and enter the beam chamber in less than 250 ms. The dump should be used 200000 times per year, with a lifetime of 20 years, with almost zero maintenance. The new challenging design is based on an oscillating thin blade shaving turn after turn the circulating beam. The material considered for the blade are Cu, Ti or CuCrZr with embedded cooling channels.

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WEPVA110

Analysis and Operational Feedback on the New Design of the High Energy Beam Dump in the CERN SPS

vacuum, operation, shielding, interlocks

3524

P. Rios Rodriguez, J.A. Briz Monago, M. Calviani, K. Cornelis, S. De Man, R. Esposito, S.S. Gilardoni, B. Goddard, J.L. Grenard, D. Grenier, M. Grieco, J. Humbert, V. Kain, F.M. Leaux, C. Pasquino, A. Perillo-Marcone, J.R.F. Poujol, S. Sgobba, D. Steyart, F.M. Velotti, V. Vlachoudis
CERN, Geneva, Switzerland

CERN's Super Proton Synchrotron (SPS) high-energy internal dump (Target Internal Dump Vertical Graphite, known as TIDVG) is required to intercept beams from 10² to 450 GeV. The equipment installed in 2014 (TIDVG#3) featured an absorbing core composed of different materials surrounded by a water-cooled copper jacket, which hold the UHV of the machine. An inspection of a previous equipment (TIDVG#2) in 2013 revealed significant beam induced damage to the aluminium section of the dump, which required imposing operational limitations to minimise the risk of reproducing this phenomenon. Additionally, in 2016 a vacuum leak was detected in the dump assembly, which imposed further limitations, i.e. a reduction of the beam intensity that could be dumped per SPS supercycle. This paper presents a new design (TIDVG#4), which focuses on improving the operational robustness of the device. Moreover, thanks to the added instrumentation, a careful analysis of its performance (both experimentally and during operation) will be possible. These studies will help validating technical solutions for the design of the future SPS dump to be installed during CERN's Long Shutdown 2 in 2020 (TIDVG#5).

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WEPVA116

HL-LHC Inner Triplet Powering and Control Strategy

controls, quadrupole, luminosity, hadron

3544

S. Yammine, H. Thiesen
CERN, Geneva, Switzerland

In order to achieve the target 3000 fb-1 integrated field for the HL-LHC (High Luminosity ' Large Hadron Collider) at ATLAS and CMS, new large aperture quadrupoles are required for the final focusing triplet magnets before the interaction points. These low-' magnets, based on the Nb3Sn technology, deliver a peak field of 11.4 T. They consist of two outer quadrupoles, Q1 and Q3 and a central one divided into two identical magnets, Q2a and Q2b. To optimize the powering and the beam dynamics of these triplets, the quadrupoles will be powered in series by a single high-current two quadrants (2-Q) converter [18 kA, ±10 V]. Three 4-Q trim power converters are added over Q1 [±2 kA, ±10 V], Q2a [±0.12 kA, ±10 V] and Q3 [±2 kA, ±10 V] to account for possible transfer function difference between the quadrupoles. This paper presents the powering scheme of the four mentioned coupled circuits. A digital control strategy, using four standard LHC digital controllers, to decouple the four systems and to achieve a high precision control is proposed and discussed.

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WEPVA120

Beam Dynamics Simulation for EPU200 in TPS

emittance, electron, storage-ring, undulator

3551

M.-S. Chiu, C.H. Chen, J.Y. Chen, P.J. Chou, T.Y. Chung, Y.-C. Liu, F.H. Tseng
NSRRC, Hsinchu, Taiwan

The Taiwan Photon Source (TPS) is a low-emittance 3-GeV light source at Natioal Synchrotron Radiation Research Center (NSRRC). Five in-vacuum undulator beamlines were delivered to users on Sep. 22, 2016. To generate 10 ~ 500 eV photon with variuos polarizations, users proposed a new EPU : EPU200. In this paper, we present the preliminary results of beam dynamics simulation for EPU200.

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WEPVA121

Thermal Experimet Results on TPS Beam Position Monitors

impedance, cavity, storage-ring, vacuum

3554

Y.T. Huang, C.K. Chan, J. -Y. Chuang, I.C. Sheng, Y.C. Yang
NSRRC, Hsinchu, Taiwan

Beam position monitors mounted in straight sections exhibit an unusual temperature rise which is attributed to poor thermal and electrical conductivity of the stainless steel BPM chamber, to the vicinity to RF-bellows, and the large button electrode size to get superior signal levels. Thermocouples tied to BPM flanges and RF bellows show that the temperature could reach 50 oC when storing a beam current of 400 mA and BPMs located between two RF-bellows in RF cavity sections responds by even 5-10 oC higher values than average. To resolve this issue, off site experiments and simulations were conducted to further understand the heat flow in the whole structure. In this paper we discuss more details of these studies.

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WEPVA127

Design of a 3.5 T Superconducting Multipole Wiggler

vacuum, radiation, photon, wiggler

3564

J.C. Jan, C.-H. Chang, H.-H. Chen, S.D. Chen, T.Y. Chung, C.-S. Hwang, F.-Y. Lin, G.-H. Luo
NSRRC, Hsinchu, Taiwan

A 3.5 T superconducting multipole wiggler (SMPW) has been designed through the collaboration of National Synchrotron Radiation Research Center (NSRRC) and Synchrotron Light Research Institute (SLRI). The SMPW will support the hard X-ray source for the X-ray absorption spectroscopy (XAS) beamline in SLRI. The design concept of the SMPW follows from, and improves on, the operating experience of the superconducting magnet in NSRRC. An improvement of the operation and compatible with the cooling capacity of the cryogenic system, is the design goal. A quick and easy recovery of the magnet from a quench event is also required. The design of the magnet circuit and the mechanical of the SMPW are also discussed herein.

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WEPVA130

Simulation the Iterative Learing Control Applied to the TPS Booster Ring Quadruple Magnet Power Supply

controls, booster, power-supply, feedback

3574

B.S. Wang, Y.-C. Chien, C.Y. Liu, K.-B. Liu, Y.S. Wong
NSRRC, Hsinchu, Taiwan

In the newly built TPS (Taiwan Photon Source), the AC power supplies of the Booster ring are required to operate in DC and AC mode with accuracy. Especially in AC mode, during the booster ramping process, the current ramping profiles of the Quadruple Magnets have to track that of the Dipole AC power supply with precise phase and amplitude to maximize the beam energy boost efficiency. At the present time, analog controllers are used for all the booster supplies and the tracking waveforms are generated externally in an EPICS control unit, converted to analog signals with precision Digital-to-Analog Converters (DACs) and then distributed to all the booster power supplies with differential signal pairs. In this paper, here we propose a hybrid iterative learning control algorithm combined with discrete PID feedback controller with the objective to eliminate the signal integrity problem inherent in analogue signals, so that boosting the beam energy might become more reliable. The proposed digital controller algorithm for the TPS booster ring magnet power supply and quadruple magnet load has been simulated with success.

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WEPVA132

Switching Power Supply Automatic Test System in Taiwan Photon Source

radiation, photon, power-supply, synchrotron

3580

Y.S. Wong, C.Y. Liu, K.-B. Liu, B.S. Wang
NSRRC, Hsinchu, Taiwan

This paper studies the use of a novel switching power supply automatic test system used in Taiwan photon source, Model 8000 is the ultimate solution for power electronic testing, the system includes a wide range of hardware choice such as AC/DC source, electronic loads, DMM, oscillate scope, noise analyzer and short/OVP tester. The ATS 8000 system uses a unique test command optimazation technology to prevent repetitive control commands from being sent to system hardware devices. This improve test speed dramatically and makes ideal choice for both high speed production applications as well as design verification.

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WEPVA134

Impedance Measurement of Vacuum Chamber Components for the Advance Photon Source (APS) Upgrade

impedance, cavity, vacuum, photon

3583

M.P. Sangroula
IIT, Chicago, Illinois, USA
R.M. Lill, R.R. Lindberg, X. Sun
ANL, Argonne, Illinois, USA

Funding: U.S. Department of Energy, Office of Science, Office of Basic Energy Sciences, under Contract No. DE-AC0206CH11357.
The proposed Advance Photon Source Upgrade (APS-U) employs a multi-bend achromat (MBA) lattice to increase the photon brightness by two to three orders of magnitude. One of the main design challenges of the upgrade is to minimize rf heating and collective instabilities associated with the impedance of small-aperture vacuum components. As part of this effort, my research focuses on impedance measurement and simulation of various MBA vacuum components. Here, we present the summary of the impedance contributions for the APS-U and describe our planned impedance measurement technique, including some measurement results for the non-evaporative getter (NEG)-coated copper chamber and simulation results for other critical components using a novel Goubau line (G-line) set up.

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WEPVA136

Vacuum System for the Diamond Light Source DDBA Upgrade

vacuum, dipole, electron, photon

3587

M.P. Cox, M.J. Duignan, R. Howard, S.C. Lay, A.G. Miller, H.S. Shiers, A. Wolfenden
DLS, Oxfordshire, United Kingdom

One cell of the Diamond Light Source (Diamond) storage ring was upgraded in late 2016 to a Double Double Bend Achromat (DDBA) configuration to provide an additional mid-achromat insertion device straight. For practical reasons it was decided to use discrete non-evaporable getter (NEG) pumps rather than NEG coatings. This paper outlines the vacuum design of the up-grade, the reasons for the choices made and the vacuum simulation tools used as well as describing the vacuum system engineering, assembly, installation and commissioning. The measured vacuum performance is found to be in close agreement with the simulations and a simple expression is derived for the beam gas lifetime.

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WEPVA142

Active Compensation Coils in the Fermilab g-2 Experiment

multipole, dipole, experiment, storage-ring

3602

K.E. Badgley
Texas A&M University, College Station, USA
B. Kiburg
Fermilab, Batavia, Illinois, USA
M.W. Smith
University of Washington, CENPA, Seattle, USA

The recently commissioned Fermilab muon g-2 experiment is aiming to determine the anomalous magnetic moment of the muon to 140 ppb. To achieve this level of precision, the magnetic field seen by the muon must be know at fraction of a ppm level, which puts limits on the required magnetic field uniformity. In addition to the mechanical adjustments made to magnet pole tips, a set of 200 trim coils were added to the ring. These coils form concentric rings with 100 on the top pole and 100 on the bottom. Measurements of the remaining integrated filed errors were made using NMR probes. The use of these trim coils to reduce the remaining higher order field errors will be discussed.

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THPAB002

Update of the Collective Effects Studies for Sirius

impedance, radiation, undulator, operation

3680

F.H. de Sá, H.O.C. Duarte, L. Liu
LNLS, Campinas, Brazil

An updated impedance budget for Sirius, with contributions from 3D electromagnetic simulations and analytic calculations, is presented and the estimates for single and multi-bunch instability thresholds for the first operation phase are re-evaluated.

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THPAB003

Harmonic RF System for the ESRF EBS

cavity, impedance, beam-loading, synchrotron

3684

N. Carmignani, J. Jacob, B. Nash, S.M. White
ESRF, Grenoble, France

A harmonic RF system for bunch lengthening to increase the Touschek lifetime of the ESRF Extemely Brilliant Source (EBS) is under study. Multiparticle simulations have been performed to study the bunch lengthening and the bunch shape with impedance effect and with third or fourth harmonic cavities. The effect of a harmonic RF system on the microwave instability is studied, finding an increase in the threshold. The AC Robinson instability threshold with a superconducting harmonic cavity has been studied with multiparticle simulations.

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THPAB005

Improvement of the Analytic Vlasov Solver DELPHI

impedance, synchrotron, proton, hadron

3688

D. Amorim
Université Grenoble Alpes, Grenoble, France
N. Biancacci, K.S.B. Li, E. Métral
CERN, Geneva, Switzerland

The simulation code DELPHI is an analytic Vlasov solver which allows to evaluate the beam transverse stability with respect to impedance effects. It allows to perform fast scans over parameters such as chromaticity, damper gain or beam intensity for a given impedance model and particle distribution. In order to improve the simulation code, new longitudinal particle distributions have been implemented. The simulations results obtained with these distributions are compared to theoretical predictions. An additional post-processing of DELPHI's output has also been implemented, allowing to reconstruct the signal seen by head-tail stripline monitors, in particular in presence of bunch-by-bunch damper. The results are compared to theoretical models, to pyHEADTAIL simulations and to measurements performed in the LHC.

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THPAB006

Nuage, Ion Cloud Tracker

ion, electron, storage-ring, injection

3692

A. Gamelin, C. Bruni, D. Radevych
LAL, Orsay, France

Funding: Work is supported by ANR-10-EQPX-51, by grants from Région Ile-de- France, IN2P3 and Pheniics Doctoral School.
NUAGE is a data parallel Matlab code which simulates the ion cloud effect in electron storage rings. The ion cloud is tracked in the ring taking into account the transverse and longitudinal effect of the beam-ion interaction, tracking in magnetic elements, usage of electrodes and gaps as clearing means. This program has been used to compute ionised ion equilibrium state and its neutralisation factor. In this article the NUAGE code is presented. The model, analysis method and performances are discussed.

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THPAB007

Short Bunches at the Transition From Strong to Weak Longitudinal Instability

shielding, synchrotron, damping, experiment

3696

P. Kuske
HZB, Berlin, Germany

The interaction of particles with their vacuum sur-roundings can lead to longitudinal instabilities of the whole bunch of particles. Most of these instabilities are strong and the growth rates are large compared to the damping rate. For a weak instability the opposite is true and with just a resistive impedance the instability would always be weak and independent of the bunch length. The interaction of a bunch with its own radiation emitted midway between parallel plates leads to a strong instabil-ity for long bunches and a transition to weak instability if the bunch length becomes shorter. This regime is ana-lysed numerically with a Vlasov-Fokker-Planck solver. The results are compared to recent observations at ANKA. An attempt is made to explain the remaining discrepan-cies by including higher order terms of the momentum compaction factor into these calculations. There are indi-cations that the simple model needs refinements in order to take radiation from upstream dipoles into account.

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THPAB008

Particle Swarm Optimization Algorithm Applied in Online Commissioning at the MLS and BESSY II

sextupole, injection, storage-ring, dynamic-aperture

3700

J. Li, J. Feikes, P. Goslawski, M. Ries
HZB, Berlin, Germany

Particle Swarm Optimization (PSO) is a population based optimization technique inspired by the social behaviour of bird flocking. This algorithm has been successfully used for beam dynamics simulation due to its excellent capability to deal with large-dimensional optimization problems. At the MLS and BESSY II PSO was first successfully applied to improve the lifetime by 20~30% within only 10 iterations respectively. Now the PSO has been implemented as a multifunctional online optimizer to improve the machine performance. This paper presents some results of online experiments.

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THPAB013

A Fast Particle Tracking Tool for the Simulation of Dielectric Laser Accelerators

laser, GPU, space-charge, plasma

3716

F. Mayet, R.W. Aßmann, U. Dorda, W. Kuropka
DESY, Hamburg, Germany
W. Kuropka, F. Mayet
University of Hamburg, Institut für Experimentalphysik, Hamburg, Germany

Funding: GBMF - Gordon and Betty Moore Foundation
In order to simulate the beam dynamics in grating based Dielectric Laser Accelerators (DLA) fully self-consistent PIC codes are usually employed. These codes model the evolution of both the electromagnetic fields inside a laser-driven DLA and the beam phase space very accurately. The main drawback of these codes is that they are computationally very expensive. While the simulation of a single DLA period is feasible with these codes, long multi-period structures cannot be studied without access to HPC clusters. We present a fast particle tracking tool for the simulation of long DLA structures. DLATracker is a parallelized code based on the analytical reconstruction of the in-channel electromagnetic fields and a Boris/Vay-type particle pusher. It computational kernel is written in OpenCL and can run on both CPUs and GPUs. The main code is following a modular approach and is written in Python 2.7. This way the code can be easiliy extended for different use cases. In order to benchmark the code, simulation results are compared to results obtained with the PIC code VSim 7.2.

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THPAB014

An Adaptive Mesh-Based Method for the Efficient Simulation of LSC-Driven Microbunching Gain in FEL Applications

electron, FEL, bunching, acceleration

3720

Ph. Amstutz
University of Hamburg, Institut für Experimentalphysik, Hamburg, Germany
M. Vogt
DESY, Hamburg, Germany

Electron beams with high peak current as they are required for the operation of free-electron lasers (FELs) are often generated by means of a series of magnetic bunch compressors. In conjunction with a collective coherent force, e.g. longitudinal space-charge (LSC), bunch compressors can possibly cause a wavelength dependent amplification of initial density inhomogeneities, potentially to an extent detrimental to the operation of the FEL. A common model, consisting of LSC, acceleration (kicks), and magnetic chicanes (drift-type maps), is governed by a time-discrete Vlasov-Poisson system. Such systems have been successfully simulated using mesh based representations of the phase space density (PSD) and the method of characteristics for the update step. However, for the irregular and exotic PSDs, prevalent in FEL applications, a homogeneous high resolution discretization on a naive rectangular mesh can be prohibitively wasteful. Here we present an approach based on adaptive tree refinement that addresses the complexity of the PSDs and allows for the efficient simulation of LSC-driven micro-bunching in FELs.

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THPAB016

Investigation on the Ion Motion Towards Clearing Electrodes in an Accelerator

ion, electron, linac, software

3723

G. Pöplau
COMPAEC e.G., Rostock, Germany
A. Meseck
HZB, Berlin, Germany

High brightness beams provided by linac-based accelerators require several measures to preserve their high quality and to avoid instabilities, where the mitigation of the impact of residual ions is one of these measures, in particular if high repetition rates are aimed for. Over the last decade three ion-clearing strategies: clearing electrodes, bunch gaps and beam shaking have been applied to counteract the degrading impact of the ions on the electron beam. Currently, their merit as clearing strategies for next generation high brightness accelerators such as energy recovery linacs (ERLs) are under intensive investigations with both simulations and measurements. In this paper, we present numerical studies for the behavior of ions generated by electron bunch passages within the field of electrodes. The objective is to investigate the ion motion towards the electrodes and to study under which circumstances and up to which ratio, equilibrium between ion generation and ion-clearing is established. Hereby several ion species and shapes of electrodes are considered with typical parameters of future high current linacs.

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THPAB019

PSPA, a Web Platform for Simulation of Particle Accelerator

lattice, linac, interface, positron

3730

M.E. Biagini, A. Variola
INFN/LNF, Frascati (Roma), Italy
L. Garnier, H. Guler, C. Helft, G. Le Meur, M. Nicolas, A. Pérus, F. Touze
LAL, Orsay, France

PSPA (Platform for Simulation of Particle Accelerators) is an original web-based interactive simulation platform for designing and modelling particle accelerators created at Laboratoire de l'Accélérateur Linéaire, Orsay. It aims at eventually containing all the tools to make a start-to-end simulation of an accelerator, and make it possible to run interactively several open source simulations codes available worldwide. At the moment, the focus is on electron/positron accelerators. PSPA will optimize the work of accelerator designers by factoring once and for all the tedious, time-consuming and error prone process of translating data formats between the various codes involved in the modelling of a machine, controlling the repeated execution of these models by easily varying some parameter and managing the associated data. Moreover, as a truly innovative feature, it will provide a convenient means for testing different physical models of a given part of a machine. The status of the project is described in this paper, and examples of its application to the ThomX compact Compton backscattering source at LAL are presented.

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THPAB021

Wake Field and Head-Tail Instability in Beam-Beam Collision with a Large Crossing Angle

wakefield, electron, positron, dipole

3738

K. Ohmi, D. Zhou
KEK, Ibaraki, Japan
N. Kuroo
UTTAC, Tsukuba, Ibaraki, Japan
K. Oide, F. Zimmermann
CERN, Geneva, Switzerland

Head-tail type of coherent beam-beam instability has been seen in a strong-strong beam-beam simulation for collision with a large Piwinski angle σ_zθ/σ_x>>1, where θ is a half crossing angle. Beta x* is key parameter for the instability. The instability is not serious for SuperKEKB, but can be seen in phase II commissioning stage. It has a large impact for design of FCC-ee. We introduce wake field due to the beam-beam collision. The wake field gives turn-by-turn correlation of head-tail mode. Head-tail instability caused by the wake field explains that seen in the strong-strong beam-beam simulation.

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THPAB022

Ion Instability in SuperKEKB Phase I Commissioning

ion, feedback, betatron, vacuum

3741

K. Ohmi, H. Fukuma, Y. Suetsugu, M. Tobiyama
KEK, Ibaraki, Japan

Ion instability has been observed in SuperKEKB phase I commissioning. Unstable modes, their growth rates, tune shift were measured. Frequency of the unstable modes is slower than theoretical prediction and the growth rate is also slower. We discuss possible model to explain the measurements.

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THPAB024

Emittance Growth at Charge-Exchanging Multi-Turn Injection in KURRI FFAG

injection, emittance, acceleration, scattering

3747

T. Uesugi, Y. Ishi, Y. Kuriyama, Y. Mori
Kyoto University, Research Reactor Institute, Osaka, Japan

In the fixed field alternating gradient (FFAG) synchrotron in Kyoto university research reactor institute (KURRI), rapid beam loss of factor 100 is observed right after the injection. In the synchrotron, charge-exchanging multi-turn injection is adopted with a stripping foil located on the closed orbit of the injection energy. No bump orbit system is used and the injected beams escape from the foil according to the closed-orbit shift by acceleration. The particles hit the foil many times and that is why the emittance grows up during the injection. In this paper, simulation studies are done to estimate the emittance growth and beam losses. The scattering effect at the foil is modeled by GEANT4.

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THPAB025

Simulation Studies of Transverse Beam Instabilities and Measures Beyond 1 MW Beam Power in the 3-GeV RCS of J-PARC

impedance, injection, acceleration, extraction

3750

P.K. Saha, H. Hotchi, Y. Shobuda
JAEA/J-PARC, Tokai-Mura, Naka-Gun, Ibaraki-Ken, Japan

The transverse impedance of the extraction kicker magnets is a significant beam instability source in the 3-GeV RCS (Rapid Cycling Synchrotron) of J-PARC (Japan Proton Accelerator Research Complex). The systematic simulation studies for beam instability by including the space charge effect has been done by using the ORBIT code. The simulation results are well reproduced in the corresponding measurements. The designed 1 MW beam power has recently been accomplished by keeping sextuple magnets off in order to stabilize the beam by utilizing the large lattice chromaticity throughout the entire acceleration period. The RCS simultaneously delivers extracted beam to the MLF (Material and Life Science Experimental Facility) and the MR (Main Ring). In order to ensure 1 MW beam power at the MLF even when RCS beam sharing to the MR is twice increased as well as when a second target station is constructed at the MLF, a beam power of 1.5 MW has to be realized in the RCS. However, the simulation shows that beyond 1 MW the beam is unstable even if no chromaticity is corrected. A reduction of the kicker impedance by at least a half is required in order to achieve 1.5 MW beam power in the RCS.

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THPAB026

Feasibility Analysis of Emittance Preservation During Bunch Compression in the Presence of Coherent Synchrotron Radiation in an Arc

emittance, dipole, lattice, synchrotron

3753

X.Y. Huang, X. Cui, S. Gu, Y. Jiao, G. Xu
IHEP, Beijing, People's Republic of China

Electron beam with low transverse emittance, short bunch length and high peak current is the basic requirement in modern high-brightness light sources. However, coherent synchrotron radiation (CSR) will dilute the transverse emittance when the electron beams pass through a magnetic bunch compressor and degrade the performance of the machine. In this paper, based on our CSR point-kick analysis, arc compressors with high compression factor in the presence of CSR effect are studied, both periodic and aperiodic arcs are included. Through analytical and numerical research, an easy optics design technique is introduced to minimize the emittance dilution within these compressors. Taking practical considerations into account, the results of periodic and aperiodic arcs are compared.

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THPAB027

Symplectic Multi-Particle Tracking Using Cuda

GPU, space-charge, kicker, emittance

3756

Zh.C. Liu
IHEP, Beijing, People's Republic of China
J. Qiang
LBNL, Berkeley, California, USA

Funding: Work supported by the U.S. Department of Energy under Contract No. DE-AC02-05CH11231 and the Ministry of Science and Technology of China under Grant No.2014CB845501.
The symplectic tracking model can preserve phase space structure and reduce non-physical effects in long term simulation. Though this model is computationally expensive, it is very suitable for parallelization and can be accelerated significantly by using Graphic Processing Units (GPUs). Using a single GPU, the code achieves a speedup of more than 400 compared with the time on a single CPU core. It also shows good scalability on a GPU cluster at Oak Ridge Leadership Computing Facility. In this paper, we report on the GPU code implement, the performance test on both single-GPU and multi-GPU cluster, and an application of beam dynamics simulation.

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THPAB029

Simulation of the Single Bunch Instabilities for the High Energy Photon Source

impedance, injection, operation, photon

3760

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

Funding: Work supported by Natural Science Foundation of China (No.11605212).
Timing modes pursing a large single bunch charge will be important operation modes for the green-field High Energy Photon Source (HEPS). The single bunch instabilities are simulated with the elegant tracking code, based on the current impedance budget. In particular, a novel on-axis accumulation scheme* based on the RF gymnastics of an active double-RF system was proposed as a candidate injection scheme for HEPS, while the zero-current rms bunch length dramatically decreases during the injection, from 32 mm to 3 mm, over a time duration of about 200 ms. The single bunch instabilities are evaluated for both the operation mode with optimal bunch lengthening as well as the injection mode with the very short bunch length, as a first step in understanding the possible beam instability for this injection scheme.
* G. Xu, et al., in Proc. IPAC'16, pp. 2886-2888. Z. Duan, et al., in Proc. eeFACT 2016.

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THPAB031

Study of Beam Break Up in Irradiation Linacs

wakefield, linac, electron, experiment

3767

X.C. Meng, H.B. Chen, W. Gai, J. Shi, S.X. Zheng
TUB, Beijing, People's Republic of China
G.H. Li, J.S. Liu, Y.H. Liu
NUCTECH, Beijing, People's Republic of China
F.H. de Sá
LNLS, Campinas, Brazil

Many recent experiments of the irradiation linacs produced at Tsinghua University indicate that beam power is limited by beam break up (BBU). Limits exist while the beam current or the pulse width is increased. In this paper, we illustrate the bream break up (BBU) phenomenon in the cases of both the 10MeV travelling-wave linac and 10MeV backward travelling-wave linac. The higher order modes in the linacs are analysed and the wake fields are calculated both with theoretical analysis and numerical simulation. Also, the beam dynamics is studied on the basis of the wakefield results to find a BBU threshold in these structures.

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THPAB038

DYNAC: Extensions, Updates, and Upgrades

lattice, operation, linac, quadrupole

3784

S. Molloy, E. Tanke
ESS, Lund, Sweden

DYNAC is a multi-particle beamline simulation code suitable for modelling of the motion of protons, heavy ions, or electrons, moving through linear accelerators and beam transport lines. In this paper, we document extensions written in Python. It will be shown how these Python extensions add a considerable amount of flexibility to DYNAC, while maintaining the calculation speeds available from the core Fortran source. Real-world use-cases are discussed. In addition, some improvements that have been made to the DYNAC source are reported.

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THPAB040

Destabilising Effect of Linear Coupling in the LHC

coupling, damping, octupole, operation

3791

L.R. Carver, D. Amorim, N. Biancacci, X. Buffat, K.S.B. Li, E. Métral, B. Salvant, M. Schenk
CERN, Geneva, Switzerland

During operation in 2015 and 2016, some transverse instabilities were observed when either the coupling (or closest tune approach) C- was large, or when the tunes were moved closer together. This motivated a campaign of simulations on the effect of linear coupling on the transverse stability. Measurements made during operation and with dedicated beam time have been found to confirm the predictions. This paper will detail the results of the linear coupling studies and relate them to operation of the LHC in the future.

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THPAB041

Implementation of Hollow Electron Lenses in SixTrack and First Simulation Results for the HL-LHC

electron, collimation, octupole, proton

3795

M. Fitterer, R. De Maria, S. Redaelli, K.N. Sjobak, J.F. Wagner
CERN, Geneva, Switzerland
G. Stancari, A. Valishev
Fermilab, Batavia, Illinois, USA

Funding: Fermilab is operated by Fermi Research Alliance, LLC, under Contract DE-AC02-07CH11359 with the US Department of Energy.
Electron lenses have found a wide range of applications for hadron colliders, where the main applications are machine protection and beam-beam compensation. This paper summarizes the status of the current electron lens implementation in SixTrack with the focus on hollow electron beams for beam collimation and shows some first simulation results of the High-Luminosity upgrade of the LHC (HL-LHC).

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THPAB042

Long-Range Beam-Beam Orbit Effects in LHC, Simulations and Observations From Machine Operation in 2016

luminosity, operation, emittance, closed-orbit

3799

A.A. Gorzawski, K. Fuchsberger, M. Hostettler, T. Pieloni, J. Wenninger
CERN, Geneva, Switzerland

To limit the number of head on collisions to only one at the interaction point in the Large Hadron Collider (LHC), two beams are colliding with a non zero crossing angle. Under the presence of such angle the closed orbits of the individual bunches in the bunch train varies due to the long-range beam-beam effects. These variations leave a signature as a non zero transverse offset at the collision points visible in the front and trail of the bunch train. When operation team aims for the optimised beam orbit and therefore maximised luminosity, those front and tail bunches due to the overall offset experience reduced luminosity. This paper describes an overview of the existing tool for simulating these effects and compares to operational data. The effects of different operational scenarios (i.e. beam brightness, reduced or asymmetric crossing angles between the interaction points etc.) are simulated and discussed.

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THPAB043

Evolution of Python Tools for the Simulation of Electron Cloud Effects

electron, interface, hadron, toolkit

3803

G. Iadarola, E. Belli, K.S.B. Li, L. Mether, A. Romano, G. Rumolo
CERN, Geneva, Switzerland

PyECLOUD was originally developed as a tool for the simulation of electron cloud build-up in particle accelerators. Over the last five years the code has become part of a wider set of modular and scriptable python tools that can be combined to study different effects of the e-cloud in increasingly complex scenarios. The Particle In Cell solver originally included in PyECLOUD later developed into a stand-alone general purpose library (PyPIC) that now includes advanced features like a refined modeling of curved boundaries and optimized resolution based on the usage of nested grids. The effects of the e-cloud on the beam dynamics can be simulated interfacing PyECLOUD with the PyHEADTAIL code. These simulations can be computationally very demanding due to the multi-scale nature of this kind of problems. Hence, a dedicated parallelization layer (PyPARIS) has been recently developed to profit of parallel computing resources in order to significantly speed-up the computation.

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THPAB044

Development of Computational Tools for Noise Studies in the LHC

GPU, Windows, emittance, beam-beam-effects

3807

S. Kostoglou, N. Karastathis, Y. Papaphilippou, D. Pellegrini, P. Zisopoulos
CERN, Geneva, Switzerland
P. Zisopoulos
Uppsala University, Uppsala, Sweden

Noise can have a significant impact on the beam dynamics in the LHC, enhancing diffusion processes and leading to emittance blowup. In order to study the details of such effects with computer simulations, a new set of tools is being developed. In particular, a demonstrator GPU-based particle tracker has been built profiting from the technology provided by the NVRTC Cuda library. Its performances for short term beam dynamic simulations in presence of many macro particles are highly promising. In addition, the Numerical Analysis of Fundamental Frequencies (NAFF) algorithm has been thoroughly inspected. Several alternatives to its fundamental steps have been investigated in a modern C++ implementation. The method was also used to produce Frequency Maps and benchmark these tools with other simulations.

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THPAB047

New Features of the 2017 SixTrack Release

electron, collimation, HOM, coupling

3815

K.N. Sjobak, J. Barranco García, R. De Maria, E. McIntosh, A. Mereghetti
CERN, Geneva, Switzerland
M. Fitterer
Fermilab, Batavia, Illinois, USA
V. Gupta
IIT, Guwahati, Assam, India
J. Molson
LAL, Orsay, France

The SixTrack particle tracking code is routinely used to simulate particle trajectories in high energy circular machines like the LHC and FCC, and is deployed for massive simulation campaigns on CERN clusters and on the BOINC platform within the LHC@Home volunteering computing project. The 2017 release brings many upgrades that improve flexibility, performance, and accuracy. This paper describes the new modules for wire- and electron lenses (WIRE and ELEN), the expert interface for beam-beam element (BEAM/EXPERT), the extension of the number of simultaneously tracked particles, the new Frequency Map Analysis (FMA) postprocessing option, the generation of a single zip of selected output files (ZIPF) in order to extend the coverage of the studies in LHC@HOME (e.g. FMA and on-line aperture checks), coupling to external codes (DYNK-PIPE and BDEX), a new CMAKE based build- and test mechanism, and internal restructuring.

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THPAB050

Simulations of Beam-Beam Interactions With RF-Track for the AWAKE Primary Beam Lines

electron, proton, plasma, space-charge

3823

J.S. Schmidt, A. Latina
CERN, Geneva, Switzerland

The AWAKE project at CERN will use a high-energy proton beam at 400 GeV/c to drive wake'elds in a plasma. The amplitude of these wake'elds will be probed by injecting into the plasma a low-energy electron beam (10-20 MeV/c), which will be accelerated to several GeV. Upstream of the plasma cell the two beams will either be transported coaxially or with an o'set of few millimetres for about 6 m. The interaction between the two beams in this beam line has been investigated in the past, with a dedicated simulation code tracking particles under the in'uence of direct space-charge e'ects. These simulations have recently been crosschecked with a new simulation code called RF-Track, developed at CERN to simulate low energy accelerators. RF-Track can track multiple-specie beams at arbitrary energies, taking into account the full electromagnetic particle-to-particle inter-action. For its characteristics RF-Track seems an ideal tool to study the AWAKE two-beam interaction. The results of these studies are presented in this paper and compared to the previous results. The implications for the facility performance are discussed.

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THPAB051

A GPU Variant of Mbtrack and Its Application in SLS-2

GPU, cavity, storage-ring, synchrotron

3827

U. Locans, A. Adelmann, L. Stingelin, H.S. Xu
PSI, Villigen PSI, Switzerland
U. Locans
University of Latvia, Riga, Latvia

Mbtrack is a widely used multi-bunch tracking code, developed at SOLEIL, for modeling the collective instabilities in electron storage rings. It has been applied to the Swiss Light Source upgrade proposal (SLS-2) for the study of single bunch instabilities. However, an n-bunch simulation using mbtrack requires to run n+1 MPI processes. Therefore, a large scale computing cluster may be necessary to perform the simulation. In order to reduce the demands of computing resources for multi-bunch simulations, a CUDA version of mbtrack has been developed, in which the computations of mbtrack are offloaded to a graphics processing unit (GPU). With the mbtrack-cuda variant, multi-bunch simulations can now run in a standalone workstation equipped with an Nvidia graphics card for scientific computing. The implementation and benchmark of the mbtrack-cuda code together with the applications in the study of longitudinal instabilities for SLS-2 will be presented.

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THPAB052

Recent Developments in DEMIRCI, the RFQ Design Software

rfq, software, ion, multipole

3830

E. Celebi
Bogazici University, Bebek / Istanbul, Turkey
O. Cakir, G. Turemen, B. Yasatekin
Ankara University, Faculty of Sciences, Ankara, Turkey
G. Turemen, B. Yasatekin
TAEK - SANAEM, Ankara, Turkey
G. Unel
UCI, Irvine, California, USA

Funding: This project has been supported by TUBITAK with project number 114F10⁶.
The RFQ design tool DEMIRCI aims to provide fast and accurate simulation of a light ion accelerating cavity and of the ion beam in it. It is a modern tool with a graphical user interface leading to a point and click method to help the designer. This article summarizes the recent developments of DEMIRCI software such as the addition of beam dynamics and 8-term potential coefficient calculations. Its results are compared to other software available on the market, to show the attained compatibility level. Finally the future prospects are discussed.

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THPAB056

Dynamic Aperture Studies of the Long-Range Beam-Beam Interaction at the LHC

emittance, luminosity, dynamic-aperture, coupling

3840

M.P. Crouch, R.B. Appleby
UMAN, Manchester, United Kingdom
J. Barranco García, T. Pieloni, C. Tambasco
EPFL, Lausanne, Switzerland
X. Buffat, M. Giovannozzi, E.H. Maclean
CERN, Geneva, Switzerland
B.D. Muratori
STFC/DL/ASTeC, Daresbury, Warrington, Cheshire, United Kingdom

Long-range beam-beam interactions dictate the choice of operational parameters for the LHC, such as the crossing angle and β^* and therefore the luminosity reach for the collider. These effects can lead to particle losses, closed orbit effects and emittance growth. Defining how these effects depend on the beam-beam separation will determine the minimum crossing angle and the β^* the LHC can operate. In this article, analysis from a dedicated machine study is presented in which the crossing angle was reduced in steps and the impact on beam intensity and luminosity lifetimes were observed. Based on the observations during the machine study, the intensity decays are compared to expectations from models. Estimates of the luminosity reach in the LHC are also computed.

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THPAB057

Method to Calculate the Longitudinal Impedance From a Partial Wakefield Simulation

impedance, wakefield, cavity, factory

3844

N.C. Shipman
UMAN, Manchester, United Kingdom
G. Burt
Cockcroft Institute, Lancaster University, Lancaster, United Kingdom
R. Calaga
CERN, Geneva, Switzerland
J.A. Mitchell
Lancaster University, Lancaster, United Kingdom

When simulating modes with high Q-factors, the wakefield length necessary to calculate the impedance spectrum can often mean a computation time of several weeks or more. A method has been developed which enables the longitudinal impedance and Q-factors of multiple modes to be calculated from a partially decayed wakefield simulation. This paper presents an overview of the method along with preliminary, proof of principle, results showing that considerable simulation time can be saved whilst maintaining a good degree of accuracy.

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THPAB059

CSR and Space Charge Studies for the CLARA Phase 1 Beamline

dipole, electron, linac, space-charge

3851

B.S. Kyle, R.B. Appleby
UMAN, Manchester, United Kingdom
J.K. Jones, P.H. Williams
STFC/DL/ASTeC, Daresbury, Warrington, Cheshire, United Kingdom
M.J. de Loos, S.B. van der Geer
Pulsar Physics, Eindhoven, The Netherlands

The installation of Phase 1 of CLARA, the UK's new FEL test facility, is currently underway at Daresbury Laboratory. When completed, it will be able to deliver 45 MeV electron beams to the pre-existing VELA beamline, which runs parallel. Phase 1 consists of a 10 Hz photocathode gun, a 2 m long S-band travelling wave linac, a spectrometer line, and associated optics and diagnostics. A detailed study into the beam dynamics of the lattice is presented, with a focus towards the effects of space charge and coherent synchrotron radiation on the electron bunch. Simulations disagreed with predictions from a one-dimensional model of coherent radiation, and this disagreement is believed to be due to a violation of the Derbenev criterion.

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THPAB061

Limiting Effects in the Double EEX Beamline

emittance, shielding, timing, dipole

3858

G. Ha
POSTECH, Pohang, Kyungbuk, Republic of Korea
M.E. Conde, D.S. Doran, J.G. Power
ANL, Argonne, Illinois, USA

Funding: This work is supported by Department of Energy, Office of High Energy Physics, under Contract No. DE-AC02-06CH11357.
The double emittance exchange (EEX) beamline is suggested to overcome the large horizontal emittance and transverse jitter issues associated with the single EEX beamline while preserving its powerful phase-space manipulation capability. However, the double EEX beamline also has potential limitations due to coherent synchrotron radiation (CSR) and transverse jitter. The former limitation arises because double EEX uses twice as many bending magnets as single EEX which means stronger CSR effects degrading the beam quality. The latter limitation arises because a longitudinal jitter in front of the first EEX beamline is converted into a transverse jitter in the middle section (between the EEX beamlines) which can cause beam loss or beam degradation. In this paper, we numerically explore the effects of these two limitations on the emittance and beam transport.

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THPAB062

Preliminary Simulations on Chirpless Bunch Compression using Double-EEX Beamline

quadrupole, emittance, controls, dipole

3862

G. Ha
POSTECH, Pohang, Kyungbuk, Republic of Korea
M.E. Conde, D.S. Doran, W. Gai, J.G. Power
ANL, Argonne, Illinois, USA

Funding: This work is supported by Department of Energy, Office of High Energy Physics, under Contract No. DE-AC02-06CH11357.
An emittance exchange (EEX) beamline can be used to compress an electron bunch via its transverse-to-longitudinal exchange mechanism. We are investigating this as an alternative to the normal magnetic chicane bunch compressor. The chicane method requires a longitudinal chirp before the chicane (since it relies on the path length difference of different energies) which results in an unwanted chirp after the compressor. Alternatively, the EEX method uses quadrupole magnets to compress the bunch. In this paper, we present preliminary simulations in preparation for a demonstration of chirp-less bunch compression using an EEX beamline at the Argonne Wakefield Accelerator facility.

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THPAB065

A Tool for Small Longitudinal Beam Dynamics in Synchrotrons

impedance, synchrotron, emittance, longitudinal-dynamics

3865

J.-F. Ostiguy, V.A. Lebedev
Fermilab, Batavia, Illinois, USA

Funding: Operated by Fermi Research Alliance, LLC under Contract No. DE-AC02-07CH11359 with the United States Department of Energy
A number of codes are available to simulate longitudinal dynamics in synchrotrons. The most established ones include TIBETAN, LONG1D, ORBIT, and ESME. While they embody a wealth of accumulated wisdom and experience, most of these codes were written decades ago and to some extent they reflect the constraints of their time. As a result, there is interest for updated tools taking better advantage of modern software and hardware capabilities. At Fermilab, the PIP-II project has provided the impetus for development of such a tool. In this contribution, we discuss design decisions and code architecture. A selection of test cases based on an initial prototype are presented.

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THPAB066

Modeling Cathode Roughness, Work Function, and Field Enhancement Effects on Electron Emission

electron, emittance, scattering, photon

3869

D.A. Dimitrov, G.I. Bell, D.N. Smithe, S.A. Veitzer
Tech-X, Boulder, Colorado, USA
I. Ben-Zvi, J. Smedley
BNL, Upton, Long Island, New York, USA
J. Feng, S.S. Karkare, H.A. Padmore
LBNL, Berkeley, California, USA

Funding: This work is supported by the US DOE Office of Science, department of Basic Energy Sciences under grant DE-SC0013190.
Recent developments in material design and growth have resulted in photocathodes that can deliver high quantum efficiency and are sufficiently robust to use in high electric field gradient photoinjectors and free electron lasers. The growth process usually produces photoemissive material layers with rough surface profiles that lead to transverse accelerating fields and possible work function variation resulting in emittance growth. To better understand the effects of surface roughness on emitted electron beams, we have developed realistic three-dimensional models for photocathode materials with grated surface structures. They include general modeling of electron excitation due to photon absorption, charge transport and emission from rough surfaces taking into account image charge and field enhancement effects. We implemented these models in the VSim particle-in-cell code. We report results from simulations using different photocathode materials with grated and flat surfaces to investigate how controlled roughness, work function variation, and field enhancement affect emission properties.

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THPAB074

MuSim, a Graphical User Interface for Multiple Simulation Programs

interface, proton, electron, storage-ring

3880

T.J. Roberts, R.J. Abrams, M.A. Cummings
Muons, Inc, Illinois, USA
Y. Bao
UCR, Riverside, California, USA

MuSim is a user-friendly program designed to interface to many different particle simulation codes, regardless of their data formats or geometry descriptions. It presents the user with a compelling graphical user interface that includes a flexible 3-D view of the simulated world plus powerful editing and drag-and-drop capabilities. All aspects of the design can be parameterized so that parameter scans and optimizations are easy. It is simple to create plots and display events in the 3-D viewer, allowing for an effortless comparison of different simulation codes. Simulation codes: G4beamline 3.02, MCNP 6.1, and MAD-X; more are coming. Many accelerator design tools and beam optics codes were written long ago, with primitive user interfaces by today's standards. MuSim is specifically designed to make it easy to interface to such codes, providing a common user experience for all, and permitting the construction and exploration of models with very little overhead. For today's technology-driven students, graphical interfaces meet their expectations far better than text-based tools, and education in accelerator physics is one of our primary goals.

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THPAB075

Accelerator Driven Subcritical Reactors for Profitable Disposition of Surplus Weapons-Grade Plutonium and Energy Generation

neutron, proton, target, operation

3883

M.A. Cummings, R.J. Abrams, R.P. Johnson, T.J. Roberts
Muons, Inc, Illinois, USA

We discuss the GEM*STAR reactor concept, which addresses all historical reactor failures, which includes an internal spallation neutron target and high temperature molten salt fuel with continuous purging of volatile radioactive fission products such that the reactor contains less than a critical mass and almost a million times fewer volatile radioactive fission products than conventional reactors like those at Fukushima. GEM*STAR is a reactor that without redesign will burn spent nuclear fuel, natural uranium, thorium, or surplus weapons material. It will operate without the need for a critical core, fuel enrichment, or reprocessing making it an excellent candidate for export. While conventional nuclear reactors are becoming more and more difficult to license and expensive to build, SRF technology development is on a steep learning curve and the simplicity implied by subcritical operation will lead to reductions in regulatory hurdles and construction complexity.

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THPAB076

Coherent Synchrotron Radiation Simulations for Off-Axis Beams Using the Bmad Toolkit

lattice, radiation, synchrotron, synchrotron-radiation

3887

D. Sagan, C.E. Mayes
Cornell University (CLASSE), Cornell Laboratory for Accelerator-Based Sciences and Education, Ithaca, New York, USA

Coherent synchrotron radiation (CSR) potentially limits operation accelerators with high bunch charges and/or short bunch lengths by increasing energy spread, and by Except at the lowest beam energies, the one dimensional treatment of coherent synchrotron radiation (CSR) originally developed by Saldin is an efficient and reasonably accurate way to simulate the effects of CSR on a particle beam. A possible problem with standard implementations of the 1D CSR formalism is that these implementations assume that the beam centroid is close to the reference trajectory that defines the lattice. In this paper, the one dimensional treatment is extended to take into account beams whose centroid is far from the reference trajectory and an example using the Cornell-BNL Fixed Field Alternating Gradient (FFAG) accelerator CBETA is given.

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THPAB077

Opal Simulations of the PSI Ring Cyclotron and a Design for a Higher Order Mode Flat Top Cavity

cavity, cyclotron, flattop, injection

3891

N. Pogue
LLNL, Livermore, California, USA
A. Adelmann, L. Stingelin
PSI, Villigen PSI, Switzerland

Funding: The research leading to these results has received funding from the European Community's Seventh Framework Programme (FP7/ 2007-2013) under grant agreement n.°290605 (PSI-FELLOW/COFUND).
The PSI cyclotron has been producing high power proton beam for 41 years. Over its lifetime it has been upgraded from producing 100 μA to 2.2 mA at 590 MeV. As the power reaches higher levels, it become more important to understand how the machine's beam dynamics will reach to new features of devices introduced. We present an OPAL (Object Oriented Parallel Accelerator Library) model of the cyclotron and compared it to the probe measurements from the machine. This model has good agreement with the measurements over the ~180 revolutions in the machine. Using this same model, a higher order mode flat top cavity was inserted into the machine to illustrate that its design and field structure allowed beam to be extracted. The HOM cavity design will also be presented. This work was performed under the auspices of the U.S. Department of Energy by Lawrence Livermore National Laboratory under Contract DE-AC52-07NA27344.

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THPAB085

Simulations of Coherent Synchrotron Radiation on Parallel Hybrid GPU/CPU Platform

GPU, radiation, emittance, synchrotron

3915

B. Terzić, D. Duffin, A.L. Godunov
ODU, Norfolk, Virginia, USA
A. Arumugam, T. Islam, D. Ranjan, S. Sangam, M. Zubair
ODU CS, Norfolk, Virginia, USA

Funding: National Science Foundation 1535641
Coherent synchrotron radiation (CSR) is an effect of self-interaction of an electron bunch as it traverses a curved path. It can cause a significant emittance degradation, as well as fragmentation and microbunching. Numerical simulations of the 2D/3D CSR effects have been extremely challenging due to computational bottlenecks associated with calculating retarded potentials via integrating over the history of the bunch. We present a new high-performance 2D, particle-in-cell code which uses massively parallel multicore GPU/GPU platforms to alleviate computational bottlenecks. The code formulates the CSR problem from first principles by using the retarded scalar and vector potentials to compute the self-interaction fields. The speedup due to the parallel implementation on GPU/CPU platforms exceeds three oders of magnitude, thereby bringing a previously intractable problem within reach. The accuracy of the code is verified against analytic 1D solutions (rigid bunch) and semi-analytic 2D solutions for the chirped bunch. Finally, we use the new code in conjunction with a genetic algorithm to optimize the design of a fiducial chicane.

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THPAB086

Long-Term Simulations of Beam-Beam Dynamics on GPUs

GPU, collider, beam-beam-effects, electron

3918

B. Terzić, C.M. Cotnoir, A.L. Godunov, T. Satogata, M. Stefani
ODU, Norfolk, Virginia, USA
A. Arumugam, R.T. Majeti, D. Ranjan, M. Zubair
ODU CS, Norfolk, Virginia, USA
F. Lin, V.S. Morozov, E.W. Nissen, Y. Roblin, T. Satogata, H. Zhang
JLab, Newport News, Virginia, USA

Funding: Jefferson Lab
Future machines such as the electron-ion colliders (JLEIC), linac-ring machines (eRHIC) or LHeC are particularly sensitive to beam-beam effects. This is the limiting factor for long-term stability and high luminosity reach. The complexity of the non-linear dynamics makes it challenging to perform such simulations which require millions of turns. Until recently, most of the methods used linear approximations and/or tracking for a limited number of turns. We have developed a framework which exploits a massively parallel Graphical Processing Units (GPU) architecture to allow for tracking millions of turns in a sympletic way up to an arbitrary order and colliding them at each turn. The code is called GHOST for GPU-accelerated High-Order Symplectic Tracking. As of now, there is no other code in existence that can accurately model the single-particle non-linear dynamics and the beam-beam effect at the same time for a large enough number of turns required to verify the long-term stability of a collider. Our approach relies on a matrix-based arbitrary-order symplectic particle tracking for beam transport and the Bassetti-Erskine approximation for the beam-beam interaction.

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THPAB088

Comparison of Theory, Simulation, and Experiment for Dynamical Extinction of Relativistic Electron Beams Diffracted Through a Si Crystal Membrane

electron, scattering, experiment, emittance

3924

L.E. Malin, W.S. Graves, J. Spence, C. Zhang
Arizona State University, Tempe, USA
R.K. Li, C. Limborg, E.A. Nanni, X. Shen, S.P. Weathersby
SLAC, Menlo Park, California, USA

Diffraction in the transmission geometry through a single-crystal silicon slab is exploited to control the intensity of a relativistic electron beam. The choice of crystal thickness and incidence angle can extinguish or maximize the transmitted beam intensity via coherent multiple Bragg scattering; thus, the crystal acts as a dynamical beam stop through the Pendel'sung effect, a well-known phenomenon in X-ray and electron diffraction. In an initial experiment, we have measured the ability of this method to transmit or extinguish the primary beam and diffract into a single Bragg peak. Using lithographic etching of patterns in the crystal we intend to use this method to nanopattern an electron beam for production of coherent x-rays. We compare the experimental results with simulations using the multislice method to model the diffraction pattern from a perfect silicon crystal of uniform thickness, considering multiple scattering, crystallographic orientation, temperature effects, and partial coherence from the momentum spread of the beam. The simulations are compared to data collected at the ASTA UED facility at SLAC for a 340 nm thick Si(100) wafer with a beam energy of 2.35 MeV.

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THPAB090

Algorithm to Calculate Off-Plane Magnetic Field From an on-Plane Field Map

optics, dipole, proton, extraction

3928

N. Tsoupas, J.S. Berg, F. Méot, V. Ptitsyn, D. Trbojevic
BNL, Upton, Long Island, New York, USA
S.A. Kahn
Muons, Inc, Illinois, USA
S. Machida
STFC/RAL/ASTeC, Chilton, Didcot, Oxon, United Kingdom

Funding: Work supported by Brookhaven Science Associates, LLC under Contract No. DE-AC02-98CH10886 with the U.S. Department of Energy.
We present an algorithm to calculate the off-plane components of the magnetic field from the on-plane components of the magnetic field which are measured on a grid of the plane. The algorithm, which is a general one and it is not restricted on a mid-plane symmetry, is based on the Taylor series expansion of the magnetic field components in terms of the normal to the plane location. The coefficients of the Taylor series expansion are expressed in terms of the on-plane derivatives of the field components which are generated by the measured magnetic field components on the grid of the plane. The algorithm is use in the RATRACE computer code[*] and has been used[**] on a dipole magnet with median plane symmetry.
* S.B. Kowalski and H.A. Enge The Ion-Optical Program Raytrace NIM A258 (1987) 407
** N. Tsoupas et. al. Effects of Dipole Magnet Inhomogeneity on the Beam Ellipsoid NIM A258 (1987) 421-425

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THPAB096

Automatized Optimization of Beam Lines Using Evolutionary Algorithms

ion, injection, operation, quadrupole

3941

S. Appel, V. Chetvertkova, W. Geithner, F. Herfurth, U. Krause, S. Reimann, M. Sapinski, P. Schütt
GSI, Darmstadt, Germany
D. Österle
KIT, Karlsruhe, Germany

Due to the massive parallel operation modes at GSI accelerators, a lot of accelerator setup and re-adjustment has to be made by operators during a beam time. This is typically done manually using potentiometers and is very time-consuming. With the FAIR project the complexity of the accelerator facility increases further and for efficiency reasons it is recommended to establish a high level of automation for future operation. Modern Accelerator Control Systems allow a fast access to both, accelerator settings and beam diagnostics data. This provides the opportunity to implement algorithms for automated adjustment of e.g. magnet settings to maximize transmission and optimize required beam parameters. The fast-switching magnets in GSI-beamlines are an optimal basis for an automatic exploration of the parameter-space. The optimization of the parameters for the SIS18 multi-turn-injection using a genetic algorithm has already been simulated*. The first results of our automatized online parameter optimization at the CRYRING@ESR injector are presented here.
[*] S. Appel, O. Boine-Frankenheim: Optimization of Multi-turn Injection into a Heavy-Ion Synchrotron using Genetic Algorithms, Proceedings of IPAC2015, Richmond, USA (2015)

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THPAB100

On the Impact of Empty Buckets on the Ferrite Cavity Control Loop Dynamics in High Intensity Hadron Synchrotrons

controls, cavity, resonance, beam-loading

3954

D. Mihailescu Stoica, D. Domont-Yankulova
Technische Universität Darmstadt (TU Darmstadt, RMR), Darmstadt, Germany
D. Domont-Yankulova, H. Klingbeil
TEMF, TU Darmstadt, Darmstadt, Germany
H. Klingbeil, D.E.M. Lens
GSI, Darmstadt, Germany

Funding: Supported by the Helmholtz Graduate School for Hadron and Ion Research
Due to technical reasons two of ten buckets have to stay empty in the planned SIS100 synchrotron at the GSI Helmholtzzentrum für Schwerionenforschung. The planned low level RF control systems consist of linear P and PI type controllers. These are responsible to maintain a desired phase and amplitude of the gap voltage. In addition the cavity is controlled to follow a prescribed resonance frequency ramp. In SIS100 the acceleration will be performed by ferrite cavities with comparatively small quality factors. Therefore, effects resulting from transient beam loading have to be expected. Influences due to empty buckets are analysed in the frequency domain and particle tracking simulations are carried out to estimate the effect on the overall system with particular consideration of emittance growth and particle loss.

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THPAB114

Operation of LLRF Control Systems in SuperKEKB Phase-1 Commissioning

controls, LLRF, cavity, operation

3986

T. Kobayashi, K. Akai, K. Ebihara, A. Kabe, K. Nakanishi, M. Nishiwaki, J.-I. Odagiri, S.I. Yoshimoto
KEK, Ibaraki, Japan
K. Hirosawa
Sokendai, Ibaraki, Japan

First beam commissioning of SuperKEKB (Phase-1), which had started in February 2016 and continued until the end of June, has been successfully accomplished. Target beam current for Phase-1 needed for sufficient vacuum scrubbing was achieved in both 7-GeV electron and 4-GeV positron rings. This presentation summarize the operation results related to low level RF (LLRF) control issues during the Phase-1 commissioning, including the system tuning, the coupled bunch instability and the bunch gap transient effect. RF system of SuperKEKB consists of about thirty klystron stations in both rings. Newly developed LLRF control system, which is composed of recent digital technique, is applied to the nine stations among the thirty for Phase-1. The RF reference signal distribution system has been also upgraded for SuperKEKB. These new systems worked well without serious problem and they contributed to smooth progress of the commissioning. The old existing systems, which had been used in the KEKB operation, were still reused for the most stations, and they also worked as soundly as performed in the KEKB operation.

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THPAB122

Open XAL Development for Xi'an Proton Application Facility

database, controls, proton, synchrotron

4010

Y. Yang, X. Guan, Y. Lei, W. Wang, X.W. Wang, S.X. Zheng
TUB, Beijing, People's Republic of China
M.C. Wang, Z.M. Wang, H.Z. Zhang
State Key Laboratory of Intense Pulsed Radiation Simulation and Effect, Northwest Institute of Nuclear Technology, Shannxi, People's Republic of China

Beam commission tools for Xi'an Proton Application Facility (XiPAF) will be developed based on Open XAL. In this paper, we present preparations made for adopting Open XAL in XiPAF, including a newly designed database schema based on MySQL, modifying db2xal application based on database schema to create optics file automatically. We also add time-dependent nodes in XiPAF's online model to meet the need of energy ramping in synchrotron. A set of high-level applications as well as a new virtual accelerator is under development.

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THPAB127

Development of 1.3 GHz Cavity Combiner for 24 kW CW SSA

cavity, coupling, linac, electromagnetic-fields

4020

W. Liu, B. Du, G. Huang, L. Lin, L. Shang, W.B. Song
USTC/NSRL, Hefei, Anhui, People's Republic of China

The 24KW CW SSA (Solid-State Amplifier) is being developed to drive the 1.3GHz SC Linac used in a THz light source. The SSA adopts the compact all-in-one combining method ' cavity combiner, which is proposed and developed in recent years. This paper reports the R&D of the cavity combiner. The cavity combiner resonates in TM010 mode, coupling with 24 coaxial-connected 1kW amplifier modules. The cavity's electromagnetic characteristic is calculated by CST, and the mechanical structure including the input and output coupler has been designed.

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THPAB128

Beam Arrival Time Analisis Based on CBPM at DCLS

cavity, experiment, FEL, undulator

4023

S.S. Cao, J. Chen, L.W. Lai, Y.B. Leng
SINAP, Shanghai, People's Republic of China
N. Zhang
SSRF, Shanghai, People's Republic of China

Dalian Coherent Light Source is the first high gain free electron lasers (FEL) user facility in China, which is dedicated at extreme ultraviolet (EUV) spectral regime of 150-50nm for various scientific fields. In its undulator section, the beam-line was equipped with ten pair of high-precision cavity beam position monitor (CBPM), which can be used for beam position and beam arrival time (BAT) measurement. Based on this, we have done some preliminary research about the beam fight time with the reference cavities of CBPMs for the future research on BAT. In this paper, we presented the scheme of the beam fight time (BFT) research, analyzed the results, and evaluated the consistency and stability of BFT.

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THPAB136

Kameleon - a Behavior-Rich, Non-Memoryless and Time-Aware Generic Simulator

status, EPICS, controls, power-supply

4040

R.N. Fernandes
ESS, Lund, Sweden
N. Senaud
CEA/DRF/IRFU, Gif-sur-Yvette, France

At ESS, thousands of devices will be used to control both the machine and end-station instruments. To enable ongoing development when access to these devices is not possible (for whatever the reason), Kameleon was implemented. It is a behavior-rich, non-memoryless and time-aware generic simulator that handles clients through a TCP/IP connection. An instance of this client is an EPICS IOC or a Tango Device Server. Kameleon consumes a user-defined file that describes the commands received from a client and, optionally, the reaction to these through statuses sent back to the client. Key features are: 1) Ubiquitous (runs in disparate platforms such as Windows and Linux). 2) Behavior-rich (predefined behaviors as well as user-defined). 3) Non-memoryless (the state of the simulation can be preserved between events and/or elapsed time). 4) Time-aware (statuses can be sent to the client either event-based or time-based). 5) Flexible (commands and statuses are described in a simple user-defined file - nothing is hard-coded in Kameleon). Kameleon will be used in a myriad of scenarios at ESS such as development of EPICS devices support, IOCs, OPI screens, testing of IOCs and alarm workflows.

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THPAB140

MAX IV Online Linac Model

linac, TANGO, GUI, controls

4047

L. Isaksson, E. Mansten, S. Thorin
MAX IV Laboratory, Lund University, Lund, Sweden

An online linac model has been developed at MAX IV in order to enable a calculation of the properties of the linac beam based on the actual settings of the magnetic elements. The model is based on the Elegant simulation code and uses the design linac lattice file. A set of Matlab scripts fetch the actual settings of all elements via the Tango control system, pass these values on to Elegant and run the simulation. The model includes an optimization option for yielding desired beta- and alpha-function values at various points along the linac by calculating optimal settings for chosen elements.

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THPAB155

Photoinjector Optimization Using a Derivative-Free, Model-Based Trust-Region Algorithm for the Argonne Wakefield Accelerator

gun, linac, emittance, laser

4100

N.R. Neveu
IIT, Chicago, Illinois, USA
J.M. Larson, J.G. Power
ANL, Argonne, Illinois, USA
L.K. Spentzouris
Illinois Institute of Technology, Chicago, Illinois, USA

Funding: DE-SC0015479, DE-AC02-06CH11357, DE-AC02-06CH11357
Model-based, trust-region, derivative-free algorithms are increasingly popular for optimizing computationally expensive numerical simulations. A strength of such methods is their efficient use of function evaluations. In this paper, we use one such algorithm to optimize the beam dynamics in two cases of interest at the Argonne Wakefield Accelerator (AWA) facility. First, we minimize the emittance of the electron bunch produced by the AWA drive rf photocathode gun alone by adjusting three parameters: rf gun phase, solenoid strength, and laser radius. The algorithm used converges to a set of parameters with an emittance of 1.08 mm-mrad. Second, we expand the number of optimization parameters to model the complete AWA rf photoinjector linac (the gun and six accelerating cavities). These results are used in a Pareto study of the trade-off between beam emittance and bunch length for the AWA linac.

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THPIK007

Production of Low Cost, High Field Quality Halbach Magnets

quadrupole, multipole, dipole, controls

4118

S.J. Brooks, J. Cintorino, A.K. Jain, G.J. Mahler
BNL, Upton, Long Island, New York, USA

Funding: Work supported by Brookhaven Science Associates, LLC under Contract No. DE-AC02-98CH10886 with the U.S. Department of Energy.
A shimming method has been developed at BNL that can improve the integrated field linearity of Halbach magnets to roughly 1 unit (1 part in 10⁴) at r=10mm. Two sets of magnets have been produced: six quadrupoles of strength 23.62T/m and six combined-function (asymmetrical) Halbach magnets of 19.12T/m with a central field of 0.377T. These were assembled using a 3D printed plastic mould inside an aluminium tube for strength. A shim holder, which is also 3D printed, is fitted within the magnet bore and holds iron wires of particular masses that cancel the multipole errors measured using a rotating coil on the unshimmed magnet. A single iteration of shimming reduces error multipoles by a factor of 4 on average. This assembly and shimming method results in a high field quality magnet at low cost, without stringent tolerance requirements or machining work. Applications of these magnets include compact FFAG beamlines such as FFAG proton therapy gantries, or any bending channel requiring a ~4x momentum acceptance. The design and shimming method can also be generalised to produce custom nonlinear fields, such as those for scaling FFAGs.

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THPIK014

Travelling Wave Accelerating Structure for Areal 50 MeV Energy Upgrade

cavity, impedance, electron, gun

4130

A. Vardanyan, V. Danielyan, S.G. Dekhtiarov, B. Grigoryan, L. Hakobyan, T. Markosyan, A.S. Simonyan
CANDLE SRI, Yerevan, Armenia
W. Ackermann
TEMF, TU Darmstadt, Darmstadt, Germany
A.V. Tsakanian
HZB, Berlin, Germany

AREAL facility development implies energy upgrade to 50 MeV in order to drive a THz free electron laser. To reach this goal, the installation of two 1.6 m long S-Band travelling wave accelerating sections, with nominal accel-erating gradient of 15 MV/m, are foreseen. In this paper the design study of accelerating sections along with the matching performance of RF couplers are presented. The simulations are performed using the CST Microwave Studio. The first results of the accelerating structure proto-type fabrication are discussed.

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THPIK017

Field Uniformity Preservation Strategies for the ESS DTL: Approach and Simulations

DTL, linac, drift-tube-linac, coupling

4139

G.S. Mauro, F. Grespan, A. Palmieri, A. Pisent
INFN/LNL, Legnaro (PD), Italy
P. Mereu, M. Mezzano, C. Mingioni, M. Nenni
INFN-Torino, Torino, Italy

The Drift Tube Linac (DTL) of the European Spallation Source (ESS) is designed to operate at 352.2 MHz with a duty cycle of 4 % (3 ms pulse length, 14 Hz repetition period) and will accelerate a proton beam of 62.5 mA pulse peak current from 3.62 to 90 MeV. This paper presents the approach taken in order to preserve field flatness of DTL Tanks. This strategy required a set of simulations and consequent choices about RF design of DTL cells, RF coupler tuning and compensation, cooling of the DTL cells. Outcomes of these simulations and the experimental verifications of this approach are then explained.

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THPIK021

Structural Mechanical Analysis of 4-Rod RFQ Structures in View of a Newly Revised CW RFQ for the HLI at GSI

rfq, quadrupole, linac, resonance

4142

D. Koser, H. Podlech
IAP, Frankfurt am Main, Germany
P. Gerhard, L. Groening
GSI, Darmstadt, Germany
O.K. Kester
TRIUMF, Vancouver, Canada

Funding: BMBF Contr. No. 05P15RFRBA
The High Charge State Injector (HLI) at the GSI Helmholtz Centre for Heavy Ion Research in Darmstadt, Germany, serves as one of the two injector linacs for the UNILAC as well as dedicated injector for the upcoming cw linac project for super heavy element research. As the front end of the HLI is planned to be upgraded for cw operation a newly revised cw capable RFQ structure with an operating frequency of 10⁸ MHz is required. The existent 4-rod structure, which was commissioned at the HLI in 2010, suffers from severe modulated rf power reflections originating from mechanical oscillations of the electrodes that both limit the achievable performance and impede stable operation*. Besides preceding vibration measurements that were done by GSI using a laser vibrometer**, the structural mechanical behavior of the 4-rod geometry was extensively analyzed using ANSYS Workbench. Thereby the crucial mechanical eigenmodes could be identified and their impact on the rf properties was investigated by simulations using CST MWS. A completely newly revised 4-rod RFQ design with optimized structural rigidity was developed of which a 6-stem prototype is currently being manufactured.
*P. Gerhard et al., Experience With a 4-Rod CW Radio Frequency Quadrupole, LINAC12, THPLB07
**P. Gerhard et al., In Situ Measurements of Mechanical Vibrations of a 4-Rod RFQ at GSI, LINAC14, TUPP057

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THPIK033

RF-Mechanical Design and Prototyping of the SPES RFQ

rfq, interface, vacuum, alignment

4166

L. Ferrari, A. Palmieri, A. Pisent
INFN/LNL, Legnaro (PD), Italy

The SPES RFQ is designed in order to accelerate beams in CW with A/q ratios from 3 to 7 from the Charge Breeder through the MRMS and the selection and injection lines up to the MEBT. RFQ is composed of 6 modules about 1.2 m long each. Each module is basically composed of a Stainless Steel Tank and four OFE Copper Electrodes (obtained by brazing of two subassemblies in order to spare material). A copper layer is electrodeposited on the tank inner surface and a spring joint between tank and electrode is used in order to seal the RF. In this paper the main result of the design of the RFQ (with particular focus on the RF-mechanical aspects and thermo-structural calculations), the RFQ prototyping strategy as well as the construction and assembly procedure of RFQ modules are described.

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THPIK036

Design Study of Damped Accelerating Cavity Based on the TM020-Mode and HOM Couplers for the KEK Light Source Project

cavity, HOM, damping, target

4172

T. Takahashi, S. Sakanaka, N. Yamamoto
KEK, Ibaraki, Japan

A novel damped-cavity scheme was recently proposed by Ego et al.*. In this design, TM020 resonant mode is used for beam acceleration. Power of higher-order (or lower-order) modes are extracted through cylindrical slots which are placed at the position where the magnetic fields of HOMs are strong while that of TM020 mode is zero. Extracted powers are absorbed by lossy ferrites. In this scheme, excellent HOM damping is possible while occupying less space of the straight section in storage rings. We propose in this paper an alternative design which is based on the same TM020 mode but with rod-type HOM couplers. The rod-type HOM couplers are placed where the electric fields of HOMs are strong while that of TM020 mode is zero. In this scheme, openings needed for HOM extraction can be made smaller, which is desirable for stiffening the mechanical structure of the cavity. Potential use of lossy dielectric materials is another merit. We present external Q-values of HOMs that can be achieved in this scheme, as well as an effect of HOM couplers on the TM020 mode. Our current study is directed to a 1.5 GHz higher-harmonic cavity for the proposed KEK Light Source project**.
* H. Ego et al., in Proceedings of the 11-th Annual Meeting of Particle Accelerator Society of Japan, Aug. 9-11, 2014, MOOL14 [in Japanese].
** K. Harada et al., IPAC2016, THPMB012.

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THPIK037

Simulation Study of Normal-Conducting Double RF System for the 3-GeV KEK Light Source Project

cavity, beam-loading, storage-ring, emittance

4176

N. Yamamoto, S. Sakanaka, T. Takahashi
KEK, Ibaraki, Japan

For the proposed 3-GeV KEK Light Source (KEK-LS) project*, a double RF system using 500-MHz accelerating and 1.5-GHz third-harmonic cavities is under consideration. To mitigate intrabeam scattering due to ultra-low emittance, the bunch length will be elongated using the harmonic cavities which is based on the TM020 resonant mode. An accelerating cavity based on this mode was first proposed by Ego et al.**, and we found it very suitable for the harmonic cavities due to the following reasons: 1) it has high unloaded-Q and high stored electromagnetic energy which result in the reduction of transient beam-loading effect due to bunch gaps, and 2) efficient damping of higher (or lower) order modes is possible. Our investigations based on numerical simulations predicted the bunch elongation by a factor of 3.1 when realistic bunch-gaps were assumed. To improve the bunch elongation further, we also proposed to compensate the transient beam loading with two realistic measures: 1) compensation of rf voltages due to feedforward technique, and 2) compensation using a separate rf cavity. We will present our study on the double rf system based on numerical simulations.
* K. Harada et al., IPAC2016, THPMB012.
** H. Ego et al., Proceedings of the 11-th Annual Meeting of Particle Accelerator Society of Japan, Aug. 9-11, 2014, MOOL14 [in Japanese].

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THPIK039

Multipactor Problem of J-PARC SDTL

multipactoring, cavity, linac, operation

4184

T. Ito, T. Morishita, J. Tamura
JAEA/J-PARC, Tokai-mura, Japan
K. Nanmo, T. Sugimura
KEK, Ibaraki, Japan

We have suffered from multipactor problem of some SDTL after the Great East Japan Earthquake. As a designed operating rf power of the SDTL is in the multipactor region, we had to operate at higher power of the designed one. From the result of the simulation and the observation of the SDTL cavity, it became clear that the multipactor occurred on the inner surface of the cavity. We think that one of the cause of the maultipactor is the contamination on the inner surface of the cavity, we performed the cleaning of the inner surface of the cavity by using acetone. The cleaning was very effective and the multipactor region was reduced dramatically or disappeared. The multipactor problem has not occurred since then.

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THPIK043

Design and Optimization of a 2MeV X-Band Side Coupled Accelerating Structure

coupling, impedance, linac, beam-loading

4193

H. Yuan
IHEP, Beijing, People's Republic of China

An X-band bi-period side-coupled accelerating structure has been designed in this paper. The structure's working frequency is 9.3GHz. '/2 mode is chosen for the structure's stability. There are 11 accelerating cells, the first 5 work as non-light velocity part while the other 6 work as light velocity part. After CST simulation, the coupling constant between accelerating cells and coupling cells is 5%, efficient shunt impedance is 142M'/m. For the beam dynamic analysis, the particle energy is selected to be 2 MeV and the peak current is 60 mA for the radiation dosage limits by national standard. After Pamela optimization, the particle's capture efficiency is more than 30%. To feed power into the structure, a coupler is designed in the middle of the structure and the coupling coefficient is 1.4. The structure is manufactured and the measurement result accords well with designing value.

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THPIK045

Design of a C-band Travelling-wave Accelerating Structure at IHEP

cavity, impedance, linac, wakefield

4196

J.R. Zhang, Y.L. Chi, J. Lei, H. Wang, X. Wang
IHEP, Beijing, People's Republic of China
S. Shu
Institute of High Energy Physics (IHEP), Chinese Academy of Sciences, Beijing, People's Republic of China

A C-band travelling wave accelerating structure has been developed at IHEP. The structure is a constant gra-dient type and operating with a 3'/4 mode. The total length of the structure is 1.8-meters long with 85 regular cells and two coupler cells. 2D program Superfish is used to optimize the cavity shape and the iris size. The wall cells are rounded for it can improved the Q value for about 10%. The cell irises have an elliptical profile to minimize the peak surface electric fields. In order to compatible with the compact of the short-range wake field on the beam dynamics, the average iris radius is 7.15 mm. The group velocity of the designed structure is from 2.8% to 1.4%. Between the rectangular waveguide and the accelerating structure, magnetic coupling is adopted. The coupled cavity is racetrack type in order to minimize the asymmetry in the coupler. Kyhl's method is used to match the input and output coupler.

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THPIK046

Design, Fabrication and Cold Test of a C-Band Barrel Open Cavity Pulse Compressor

cavity, coupling, klystron, vacuum

4200

S. Shu
Institute of High Energy Physics (IHEP), Chinese Academy of Sciences, Beijing, People's Republic of China
M. Hou, S. Pei, N.B. Song, J.R. Zhang, F. Zhao
IHEP, Beijing, People's Republic of China

The first prototype of the C band barrel open cavity (BOC) pulse compressor has been manufactured by the Institute of High Energy Physics (IHEP), Beijing, which is used to test the brazing process and the RF properties of the structure at low power. The whispering gallery mode TM6, 1,1 with an unload Q of 100, 000 was adopt to oscillate in the cavity, and the coupling factor was optimized to achieve the highest power gain. This paper mainly deals with the RF design, mechanical design and cold test of the C band BOC pulse compressor.

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THPIK054

The X-Band Pulse Compressor for Tsinghua Thomson Scattering X-Ray Source

cavity, coupling, klystron, scattering

4214

Y.L. Jiang, H.B. Chen, C. Cheng, W. Gai, J. Shi, P. Wang, X.W. Wu, H. Zha
TUB, Beijing, People's Republic of China

An X-band (11.424 GHz) high-power RF station is being built for Tsinghua Thomson scattering X-ray Source (TTX). The station aims to feed several X-band accelerating structures working at a high gradient of 80 MV/m. An X-band pulse compressor is designed to compress the RF pulse from 1.5 us to 100 ns and to generate more than 250 MW peak power from a 50MW klystron. This pulse compressor implements a resonate cavity housing the HE11-mode as the energy storage cavity, with a high quality factor Q of more than 10⁵. The detailed design of the high-Q cavity as well as the dedicate couplers of this pulse compressor are present in this work.

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THPIK056

Design of a C-Band High-Efficiency Multi-Beam Klystron

klystron, electron, bunching, cavity

4221

Z.N. Liu, H.B. Chen, M.M. Peng, J. Shi
TUB, Beijing, People's Republic of China

A multi-beam klystron at 5.712GHz has been designed with efficiency of more than 80%. It can generate a pulse with output power of about 3MW and a pulse length of 5 us. Space charge effect and large signal theory, which both increase the accuracy theoretically, are considered in the simulation. A series of parameters of cavities are given after optimizing, including the frequency, R/Q, Q0 and Qe. This paper describes the beam dynamics design of the klystron as well as a preliminary machenical design.

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THPIK057

Development of a High-Power X-Band RF Rotary Joint

linac, network, insertion, scattering

4224

J. Liu, H.B. Chen, J. Shi, X.W. Wu, H. Zha
TUB, Beijing, People's Republic of China

RF rotary joints allow the independent movement be-tween the RF power source and the accelerating tube of a linear accelerator (linac). In this paper, the design of a compact X-band (9.3 GHz) high-power RF rotary joint is presented. Simulation results illustrate that RF parameters (the scattering matrix) of this rotary joint keep stable in the arbitrary rotation angle. The maximum return loss is about -30 dB, the insert loss is less than 0.11 dB, and the variance of output phase shifts is below 1 degree while rotating the joint. RF measurement on the rotary joint using Vector-Network analyser is also conducted and presented in this paper.

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THPIK061

3D Model Analysis of Cavity for CSNS DTL

DTL, cavity, insertion, neutron

4236

P.H. Qu, M.X. Fan, B. Li, Y. Wang
CSNS, Guangdong Province, People's Republic of China
Q. Chen, K.Y. Gong, A.H. Li, H.C. Liu, F.X. Zhao
IHEP, Beijing, People's Republic of China

An Alvarez-type Drift tube linac (DTL) was utilized to accelerate an H⁻ ion beam from 3 MeV to 80 MeV of China Spallation neutron source (CSNS). RF field profile is always deviate from the design curve due to errors in fabrication and assembly of the structure cells, thus RF tuning of DTL is necessary. CSNS DTL operates in zero mode and has long tank, so accelerating field of which is unstable, this problem was solved through adding post couplers at the both side of cavity wall. In order to speed up the schedule of DTL low power RF tuning, we analyzed the operating mode, field flatness with slug tuners, field stabilization with post couplers by CST Micro wave studio (MWS) mainly with eigenmode solver in advance. Considering saving the computer memory and increasing the calculation speed, we divided each tank model into three short units. Slug tuner depth and PC-DT gap of DTL-1 and DTL-3 by simulation were shown which improved the efficiency of CSNS DTL RF tuning.

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THPIK063

The RF System of Infrared Free Electron Laser Facility at NSRL

cavity, electron, LLRF, laser

4239

L. Lin, B. Du, G. Huang, K. Jin, F.F. Wu
USTC/NSRL, Hefei, Anhui, People's Republic of China

Funding: The Natural Science Foundation of China
An infrared free electron laser light source (IRFEL) is being constructed at National Synchrotron Radiation Laboratory, which could be used in the study of far infrared detection, light dissociation and light excitation. The accelerator of IRFEL deliver a average current 300 A electron beam at 15~60 MeV, the energy spread is less than 240 keV, and the emittance is less than 30 mm*mrad. IRFEL is consisted of two optical resonator system, which could create 2.5~50 um, 40~200um infrared laser respectively. The design of IRFEL RF system is introduced, the recent progress of prebuncher, buncher, frequency distribution, accelerator and DLLRF system are also present in this paper.

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THPIK065

Reliability Anlysis of 20kw Solid-State Amplifiers for Ciads

controls, power-supply, target

4245

P.H. Gao
IMP/CAS, Lanzhou, People's Republic of China

CIADS will apply the solid-state amplifier. 20KW solid-state amplifiers are the basis of RF systems. This talk model 20KW solid-state amplifiers with reliability block diagram(RBD). Through simulation, we find that the reliability function relative to redundancy approximates logarithm, but cost is linear growth. There is an optimal solution between redundancy and cost.

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THPIK067

A C-Band Compact Spherical RF Pulse Compressor for the SXFEL Linac Energy Upgrade

cavity, coupling, electron, linac

4248

Z.B. Li, W. Fang, Q. Gu, Z.T. Zhao
SINAP, Shanghai, People's Republic of China

A new compact C-band (5712 MHz) spherical RF pulse compressor has been designed for Shanghai Soft X-ray Free Electron Laser (SXFEL) facility energy upgrading at Shanghai Institute of Applied Physics (SINAP), Chinese Academy of Sciences (CAS). This pulse compressor contains one high Q0 spherical RF resonant cavity which works on two TE113 modes and a novel coupler. As there is only one storage cavity, this pulse compressor can be much smaller than the traditional SLED. With the coupling coefficient 4.9, the average power gain can be as high as 3.8. In this paper, the scheme of the C-band spherical pulse compressor and RF design are presented.

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THPIK078

1.5 GHz Cavity Design for the CLIC Damping Ring and as Active Third Harmonic Cavity for ALBA

cavity, HOM, damping, impedance

4263

B. Bravo, J.M. Alvarez, F. Pérez, A. Salom
ALBA-CELLS Synchrotron, Cerdanyola del Vallès, Spain

In a collaboration framework between CERN and ALBA, we are designing 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 preliminary design of this cavity: an active, normal conducting cavity tuned at 1.5 GHz based on the 500 MHz European Higher Order Mode (HOM) damped normal conducting with nose cones using ridged circular waveguides for HOM damping. Electromagnetic simulations, mechanical and thermal stress analysis will be presented together with the calculations on beam stability improvement due to the third harmonic system.

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THPIK080

Magnetic Performance of the New ALBA Magnetic Measurements Bench for Closed Structures

cyclotron, dipole, undulator, controls

4269

J. Campmany, L.G.O. Garcia-Orta, J. Marcos, V. Massana
ALBA-CELLS Synchrotron, Cerdanyola del Vallès, Spain

ALBA has designed and built a new magnetic measurement bench for closed structures, presented elsewhere. This bench has been fully built in-house and has been magnetically characterized at ALBA, showing excellent performance in terms of repeatability and accuracy. In the case of homogeneous fields, the accuracy reaches 10 microTesla, and in the case of undulators characterization, the accuracy of period determination reach 0.5 microns and the field accuracy is 60 microTesla. After this characterization, the bench has been moved to CIEMAT premises, and has been used to magnetically characterize the superconducting magnet of the AMIT cyclotron. In this paper we present the results of magnetic characterization of the bench as well as the first results of cyclotron measurements.

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THPIK092

Considerations on the Effect of Magnet Yoke Dilution on Remanent Field at ELENA

quadrupole, antiproton, dipole, multipole

4299

C. Carli, L. Fiscarelli, D. Schoerling
CERN, Geneva, Switzerland

The Extra Low Energy Antiproton ring (ELENA) is a small synchrotron constructed at CERN to decelerate antiprotons down to 100 keV and, thus, operated at very low magnetic fields. The CERN magnet group has carried out extensive investigations on accelerator magnets for very low fields, comprising theoretical studies and the construction of several prototype magnets, to ensure that the required field quality can be reached at these very low fields. In the course of this work, experimental investigations [1] led to the initially unexpected observation that dilution of the yoke, i.e. alternating laminations made of electric steel with thicker non-magnetic stainless steel laminations, increases the remnant field. An explanation for this behaviour has already been anticipated in a previous paper [2]. Here, we treat this specific topic in analytical detail. We come to the conclusion that magnet yoke thinning in most practical situations does not improve the field quality at very low field levels, but rather enhances the impact from hysteresis and remanence effects.
[1] L.Fiscarelli, Magnetic measurements on the quadrupoles prototypes for ELENA (PXMQNLGNAP), CERN internal report.
[2] D. Schoerling, Case Study of a Magnetic System for low-Energy Machines, PRAB 19, 082401 (2016).

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THPIK093

Blow-Up Due to Intra Beam Scattering during Deceleration in ELENA

emittance, scattering, electron, antiproton

4303

C. Carli, M. Martini
CERN, Geneva, Switzerland

Intra Beam Scattering (IBS) is expected to be the main performance limitation of the Extra Low Energy Antiproton ring (ELENA), a small synchrotron equipped with electron cooling under construction at CERN to decelerate antiprotons from 5.3 MeV to 100 keV. Thus, the duration of the ramps must not be too long to avoid excessive blow up due to IBS. On the other hand, the bending magnets are C-shaped and the vacuum chambers are without insulated junctions, which are difficult for fully baked machines; thus, the ramps must not be too short. The evolution of transverse and longitudinal emittances along the ramps have been estimated assuming that IBS is the main phenomenon leading to blow-up. The blow-up due to IBS found along the ramps have been found to be acceptable.

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THPIK104

Transient Simulation of the ISIS Synchrotron Singlet Quadrupoles Using OPERA 3D

quadrupole, synchrotron, software, proton

4334

I. Rodríguez
STFC/RAL/ISIS, Chilton, Didcot, Oxon, United Kingdom

Type QX10⁶ singlet magnets are AC defocusing quadrupoles used in the ISIS main synchrotron ring. They have an aperture of 202 mm and a yoke length of 303 mm, so the end effects are significant. The iron poles and the yoke are asymmetric and the coils are driven by a 50Hz, 400 A AC current, biased with a DC current of 665 A. Therefore the yoke has to be laminated, and the laminations are slitted up to a depth of 90 mm on each side to further reduce the eddy current losses. Two 3D models (DC and transient) have been developed using OPERA 3D for different purposes. Both models require the use of an anisotropic BH curve for the yoke, and the transient model also requires an anisotropic conductivity and a prismatic/hexahedral mesh to overcome the limitations of the linear tetrahedral edge elements in OPERA's vector potential formulation. The quadrupole field quality was originally measured in 1982 with a DC excitation at the biased peak current (1065 A) and those measurements are now compared to both models. The iron losses due to the eddy currents are also presented and compared to the original specifications defined in 1980, as well as an estimation of the eddy currents in the coils.

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THPIK106

Low Power RF Characterisation of the 400 Hz Photoinjector for CLARA

cathode, cavity, linac, vacuum

4342

L.S. Cowie, P. Goudket, B.L. Militsyn
STFC/DL/ASTeC, Daresbury, Warrington, Cheshire, United Kingdom
G. Burt
Cockcroft Institute, Lancaster University, Lancaster, United Kingdom
T.J. Jones
STFC/DL, Daresbury, Warrington, Cheshire, United Kingdom

The CLARA High Repetition Rate Photoinjector comprises an S-band dual feed cavity and will operate at a repetition rate of up to 400 Hz and is capable of reaching an electric field strength on the cathode of 120 MV/m. The cavity was brazed after tuning and arrived at Daresbury Laboratory in February 2016. Extensive low power RF testing has been performed including measurements of the quality factors and coupling, pass-band mode frequencies, on axis field and RF repeatability of replacement of cathode plug. The dual feed coupler has been tuned and a Magic Tee type splitter installed. The photoinjector is now installed on the VELA beam line for commissioning and characterisation.

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THPIK107

Design and Characterisation of the Focusing Solenoidal System for the CLARA High Repetition Rate Electron Source

solenoid, multipole, alignment, cathode

4346

D.J. Scott, A.R. Bainbridge, K.B. Marinov, B.L. Militsyn, B.J.A. Shepherd
STFC/DL/ASTeC, Daresbury, Warrington, Cheshire, United Kingdom
R.J. Cash, T.J. Jones
STFC/DL, Daresbury, Warrington, Cheshire, United Kingdom
C.S. Edmonds
The University of Liverpool, Liverpool, United Kingdom

One of the critical components of electron injectors based on RF photoelectron sources is the focusing system. The system typically consists of a Main Focusing Solenoid and a Bucking Coil. Combination of these two solenoids should provide proper focusing of the beam at the exit of the RF cavity and zero longitudinal magnetic field in the photocathode plane to minimise the beam emittance. Imperfection of the solenoid design, manufacturing and alignment frequently leads to asymmetry of the focusing field which has to be compensated with additional coils. In order to eliminate mechanical and magnetic misalignment the CLARA photoinjector solenoids are mounted on one integrated bench and before installation into the beamline have been aligned in the magnet laboratory with simultaneous measurement of the magnetic field. In order to define multipole field components, dedicated measurements of the transverse magnetic field have been done. The amplitudes of the multipoles have been obtained from analysis of the transverse field map. We present here the results of field characterisation.

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THPIK110

RF Cavity Design for a Low Cost 1 MeV Proton Source

cavity, proton, acceleration, impedance

4355

D. Soriano Guillén, R. Seviour
University of Huddersfield, Huddersfield, United Kingdom
S. Hunt
Alceli Accelerator Technology Ltd., Huddersfield, United Kingdom

In this paper we present the design for a low-cost RF cavity capable of accelerating protons from 100 keV to 1 MeV. The system is designed to meet the specifications from the proposed Alceli LTD medical proton therapy linac, to deliver a 1 nA proton beam current with a 1 kHz repetition rate. We present a design of an RF normal conducting (NC) re-entrant Cu cavity operating at 40 MHz consisting of a coupled two cavity system, both driven by a single Marx generator. The choice of such a low operating frequency for the cavity system enables us to use a relatively low-cost cost Marx Generator as the RF source. Marx generators work in a similar fashion to a Cockcroft-Walton accelerator (without the expensive components), creating a high-voltage pulse by charging a number of capacitors relatively slowly in parallel, then rapidly discharging in series, via spark gaps. Marx generators can deliver 2.5 GW, 1 ns pulses, with rise times of 200 ps, and (relatively) low jitter.

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THPIK115

Status of the Perpendicular Biased 2nd Harmonic Cavity for the Fermilab Booster

cavity, Windows, booster, solenoid

4366

C.-Y. Tan, J.E. Dey, K.L. Duel, J. Kuharik, R.L. Madrak, A.V. Makarov, W. Pellico, J. Reid, G.V. Romanov, M. Slabaugh, D. Sun, I. Terechkine
Fermilab, Batavia, Illinois, USA

Funding: Operated by Fermi Research Alliance, LLC under Contract No. DE-AC02-07CH11359 with the United States Department of Energy.
This is a status report on the 2nd harmonic cavity for the Fermilab Booster as part of the Proton Improvement Plan (PIP) for increasing beam transmission efficiency, and thus reducing losses. A set of tuner rings has been procured and is undergoing quality control tests. The Y567 tube for driving the cavity has been successfully tested at both injection and extraction frequencies. A cooling scheme for the tuner and cavity has been developed after a thorough thermal analysis of the system. RF windows have been procured and substantial progress has been made on the mechanical designs of the cavity and the bias solenoid. The goal is to have a prototype cavity ready for testing by the end of 2017.

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THPIK128

Switching Magnet for Heavy-Ion Beam Separation

power-supply, flattop, magnet-design, target

4403

J.J. Hartzell, R.B. Agustsson, S.V. Kutsaev, A. Laurich, A.Y. Murokh, F.H. O'Shea, T.J. Villabona
RadiaBeam, Santa Monica, California, USA
G. Leyh
LOD, Brisbane, USA
E.A. Savin
RadiaBeam Systems, Santa Monica, California, USA

Funding: This work was supported by the United States Department of Energy SBIR Grant No. DE-SC0015124.
We present a design for a complete switching magnet system capable of deflecting 8-25 MeV/u heavy-ion beams by 10 degrees. The system can produce flat-top pulses from 1 to 30 ms with rise and fall times of less than 0.5 ms at a duty cycle of 3-91% into a heavily inductive load. As determined by physics needs, the operational parameters of this magnet place it between fast rising kicker magnets with short duration and slow rising (or DC) resistive magnets which are optimized for efficiency and current-based power loss. This magnet must operate efficiently with over 91% duty factor and have a modestly fast rise time. The resulting design uses a resistive magnet scheme, to optimize the current-based losses, that is pulsed using a new circuit to control the applied voltage. The magnet has a laminated, iron dominated, H-shaped core. Directly-cooled copper pancake coils energize the magnet. The modulator employs a novel, proprietary, over-voltage topology to overcome the inherent inductance and achieve the fast rise and fall times, switching to a precision DC supply to efficiently maintain the flattop without requiring voltage in excess of ±3 kV.

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THPVA002

Numerical Investigation of Beam Halo From Beam Gas Scattering in KEK-ATF

emittance, scattering, vacuum, damping

4410

R.J. Yang, P. Bambade
LAL, Orsay, France
K. Kubo, T. Okugi, N. Terunuma, D. Zhou
KEK, Ibaraki, Japan

To demonstrate the final focus schemes of the Future Linear Collider (FLC), the Accelerator Test Facility 2 (ATF2) at KEK is devoted to focus the beam to a RMS size of a few tens of nanometers (nm) vertically and to provide stability at the nm level at the virtual Interaction Point (IP). However, the loss of halo particles upstream will introduce background to the diagnostic instrument measuring the ultra-small beam, using a laser interferometer monitor. To help the realization of the above goals and beam operation, understanding and mitigation of beam halo are crucial. In this paper, we present the systematical simulation of beam halo formation from beam gas Coulomb scattering (BGS) in the ATF damping ring. The behavior of beam halo with various machine parameters is also discussed.

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THPVA003

Status of the Beam Dynamics Design of the New Post-Stripper DTL for GSI-FAIR

DTL, emittance, quadrupole, ion

4414

A. Rubin, X. Du, L. Groening, M. Kaiser, S. Mickat
GSI, Darmstadt, Germany

The GSI UNILAC has served as injector for all ion species since 40 years. Its 10⁸ MHz Alvarez DTL providing acceleration from 1.4 MeV/u to 11.4 MeV/u has suffered from material fatigue and has to be replaced by a new section. The design of the new post-stripper DTL is now under development in GSI. Five Alvarez tanks with four intertank sections provide 100% transmission and low emittance growth. The intertank sections allow for a matched solution and provide place for diagnostics. Simulations along the complete Alvarez DTL were done for 238U²⁸⁺ using the TraceWin code. The transversal zero current phase advance is 65' for all tanks. Results of beam dynamics simulations for six different scenarios as well as an error study for the FAIR nominal case are presented.

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THPVA005

Investigation of Electron Beam Assisted Density Boosting in Plasma Traps Using the Example of a Gabor Plasma Lens

electron, plasma, experiment, space-charge

4421

C. Beberweil, M. Droba, S. Klaproth, O. Meusel, D. Noll, H. Podlech, K. Schulte, K.I. Thoma
IAP, Frankfurt am Main, Germany
S. Gammino, D. Mascali
INFN/LNS, Catania, Italy
L. Malferrari, A. Montanari, F. Odorici
INFN-Bologna, Bologna, Italy

Gabor lenses are plasma traps that can be used for focusing an ion beam linearly without aberrations* by the electric field of a confined electron cloud. They combine strong electrostatic focusing with the possibility of space charge compensation and provide an attractive alternative to conventional ion beam optics in a LEBT section. The focusing performance strongly depends on the density and distribution of the enclosed electron plasma*. As the Gabor lens is usually operated close to the ion source, residual gas ionization is supposed to be the central electron generation mechanism. An electron source is introduced in order to investigate the possibility of boosting the electron density in plasma traps using the example of a Gabor lens. This way, a Gabor lens could be operated under XUHV conditions, where residual gas ionization is suppressed. The particle in cell code bender** was used to simulate the injection into the confining fields of the space charge lens in different geometrical configurations and a prototype experiment was constructed consisting of a Gabor lens and an electron source system. In this contribution, simulations and measurements will be presented.
* Schulte, K., et al. Electron cloud dynamics in a Gabor space charge lens. 2012
** Noll, D., et al. The particle-in-cell code bender and its application to non-relativistic beam transport. 2015

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THPVA006

Space-Charge Compensation in the Transition Area Between LEBT and RFQ

rfq, injection, electron, ion

4425

P.P. Schneider, D. Born, V.A. Britten, M. Droba, O. Meusel, H. Podlech, A. Schempp
IAP, Frankfurt am Main, Germany
D. Noll
CERN, Geneva, Switzerland

Funding: This work is supported by the German Federal Ministry of Education and Research (BMBF) #05P15RFRBA and by HORIZON 2020 for the MYRRHA project #662186
The transition from a space charge compensated beam in the LEBT to an uncompensated beam in the RFQ will influence the beam parameters. To investigate the impact of the electric fields on the space charge compensation, an insulated cone is used as a repeller electrode in front of the RFQ. Depending on the time dependent potential of the RFQ rods respectively to the beam potential, the compensation electrons may be prevented from moving into the RF field which oozes out of the RFQ entrance. The simulation studies are performed with the particle-in-cell code bender*. The simulations may substantiate measurements at the CW-operated RFQ in Frankfurt University** as well as at the foreseen MYRRHA LEBT-RFQ interface.*** In this contribution, a study on a LEBT-RFQ interface is shown. Results of numerical and experimental investigations will be compared.
*Noll, D. et al.The Particle-in-Cell Code Bender and Its Application to Non-Relativistic Beam Transport, WEO4LR02, HB'14
**Meusel, O. et al.FRANZ Accelerator Test Bench and Neutron Source.,MO3A03, LINAC'12
***R. Salemme et al.Design Progress of the MYRRHA Low Energy Beam Line, MOPP137, LINAC'14

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THPVA007

Matching Space-charge Dominated Electron Bunches into the Plasma Accelerator at SINBAD

emittance, electron, plasma, focusing

4429

J. Zhu, R.W. Aßmann, U. Dorda, B. Marchetti
DESY, Hamburg, Germany

The SINBAD facility (Short and INnovative Bunches and Accelerators at DESY) is foreseen to provide sub-fs to tens of fs electron bunches for Laser Wake-Field Acceleration (LWFA) experiments. In order to avoid emittance growth in plasma cells with ultra-high accelerating gradients the injection and transport of electron bunches with beta functions of mm-size or even smaller are required. This kind of bunch is usually space-charged dominated since the energy is low (< 200 MeV) while the peak current is high for allowing the electron bunches to be used for Free Electron-Laser (FEL) generation. We present the beamline design and explore the possible beam parameters at the SINBAD linac by start-to-end simulations.

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THPVA010

Electron Cloud Simulations for the Main Ring of J-PARC

electron, proton, detector, vacuum

4436

B. Yee-Rendón, R. Muto, K. Ohmi, K. Satou, M. Tomizawa, T. Toyama
KEK, Ibaraki, Japan

The simulation of beam instabilities is a helpful tool to evaluate potential threats against the machine protection of the high intensity beams. At Main Ring (MR) of J-PARC, signals related to the electron cloud have been observed during the slow beam extraction mode. Hence, several studies were conducted to investigate the mechanism that produces it, the results confirmed a strong dependence on the beam intensity and the bunch structure in the formation of the electron cloud, however, the precise explanation of its trigger conditions remains incomplete. To shed light on the problem, electron cloud simulations were done using an updated version of the computational model developed from previous works at KEK. The code employed the signals of the measurements to reproduce the events seen during the surveys.

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THPVA013

Benchmarking of the ESS LEBT in TraceWin and IBSimu

proton, ion, rfq, emittance

4445

Ø. Midttun
University of Bergen, Bergen, Norway
Y.I. Levinsen, R. Miyamoto, D.C. Plostinar
ESS, Lund, Sweden

The modeling of the proton beam in the ESS accelerator starts with a beam distribution as an input to the TraceWin code currently used as the simulation tool. This input is typically a Gaussian distribution, a distribution from other codes, or data from an emittance measurement. The starting point of these simulations is therefore located somewhere along the low energy beam transport (LEBT) close to the ion source. In this paper, we propose to use IBSimu to model the beam extraction from the ion source, which provides an input beam distribution to TraceWin. IBSimu is a computer simulation package for ion optics, plasma extraction, and space charge dominated ion beam transport. We also present a benchmarking of the beam tracking through the LEBT using both these tools, and propose a transition interface to handover the beam distribution from IBSimu to TraceWin.

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THPVA019

Self-consistent Space Charge Tracking Method based on Lie Transform

space-charge, proton, sextupole, emittance

4454

E. Laface, J. F. Esteban Müller
ESS, Lund, Sweden

In this paper we propose to describe the self-force of a particles beam, known as space charge, as an Hamiltonan term dependent on the distribution of the particles' coordinates: H_sc = H_sc(ρ(x,y,z)). This Hamiltonian is then used, together with the kinetic component H_k in a Lie transform to generate a transport map by e^{-L:H_k +H_sc}: where the Lie operator :H_k + H_sc: is defined according to the Dragt's notation [1]. Then the Lie transform is used to transport directly the distribution function ρ(x, y, z) in a self-consistent iterative algorithm. The result of this proof-of-concept idea is verified on a drift space and on a FODO channel and compared with a traditional multi-particles simulation code.

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THPVA020

Distribution and Extreme Loss Analysis in the ESS Linac: A Statistical Perspective

linac, proton, DTL, alignment

4458

A.L. Pedersen
Lund Institute of Technology (LTH), Lund University, Lund, Sweden
D. Anevski
Lund University, Lund, Sweden
M. Eshraqi, R. Miyamoto
ESS, Lund, Sweden

The report takes a statistical approach in the study of distribution evolution of the proton beam within the ESS linac and reports a new technique of pinpointing the non-linear space-charge effect of the propagating proton beam. By using the test statistic from the nonparametric Kolmogorov-Smirnov test the author visualises the change in the normalised distributions by looking at the supremum distance between the cumulative distribution functions in comparison, and the propagation of the deviation throughout the ESS linac. This approach identifies changes in the distribution which may cause losses in the linac and highlights the parts where the space-charge has big impact on the beam distribution. Also, an Extreme Value Theory approach is adopted in order to quantify the effects of the non linear forces affecting the proton beam distribution.

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THPVA021

Dynamics of Spectator Particles in Space-Charge Fields of Mismatched Beams With Cross-Plane Coupling

space-charge, lattice, coupling, proton

4462

M. Holz, V.G. Ziemann
Uppsala University, Uppsala, Sweden

In accelerators with high beam power, even moderate beam losses must be avoided. These losses are due to particles reaching large transverse amplitudes that form a low density halo orbiting the beam core. To study the beam halo formation, we place a spectator particle outside the beam core and let it interact with the core's electric field. The core, we model by a self-consistent transverse Gaussian beam including non-linear space charge forces and cross-plane coupling.

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THPVA022

Comparison of Different Methods to Calculate Induced Voltage in Longitudinal Beam Dynamics Codes

impedance, wakefield, dipole, damping

4465

D. Quartullo, J. Repond
CERN, Geneva, Switzerland
M. Migliorati
University of Rome La Sapienza, Rome, Italy

Collective effects in longitudinal beam dynamics simulations are essential for many studies since they can perturb the RF potential, giving rise to instabilities. The beam induced voltage can be computed in frequency or time domain using a slicing of the beam profile. This technique is adopted by many codes including CERN BLonD. The slicing acts as a frequency filter and cuts high frequency noise but also physical contributions if the resolution is not sufficient. Moreover, a linear interpolation usually defines the voltage for all the macro-particles, and this can be another source of unphysical effects. The MuSiC code describes interaction between the macro-particles with the wakes generated only by resonator impedances. The complications related to the slices are avoided, but the voltage can contain high frequency noise. In addition, since the computational time scales with the number of resonators and macro-particles, having a large number of them can be cumbersome. In this paper the features of the different approaches are described together with benchmarks between them and analytical formulas, considering both single and multi-turn wakes.

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THPVA023

Studies of Longitudinal Beam Stability in CERN PS Booster After Upgrade

impedance, space-charge, emittance, injection

4469

D. Quartullo, S.C.P. Albright, E.N. Shaposhnikova
CERN, Geneva, Switzerland

The CERN PS Booster, comprised of four superposed rings, is the first synchrotron in the LHC proton injection chain. In 2021, after major upgrades, the injection and extraction beam energies, as well as the acceleration rate, will be increased. The required beam intensities should be a factor of two higher for nominal LHC and fixed-target beams, and the currently used narrow-band ferrite systems will be replaced by broad-band Finemet cavities in all four rings. Future beam stability was investigated using simulations with the Beam Longitudinal Dynamics (BLonD) code. The simulation results for existing situation were compared with beam measurements and gave a good agreement. An accurate impedance model, together with a careful estimation of the longitudinal space charge, was used in simulations of the future acceleration cycle in single and double RF, with phase and radial loops and controlled longitudinal emittance blow-up. Since the beam is not ultra-relativistic and fills the whole ring (h=1), the front and multi-turn back wakes were taken into account, as well as the RF feedbacks which reduce the effect of the Finemet impedance at the revolution frequency harmonics.

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THPVA024

Controlled Longitudinal Emittance Blow-Up Using Band-Limited Phase Noise in CERN PSB

emittance, impedance, synchrotron, injection

4473

D. Quartullo, E.N. Shaposhnikova, H. Timko
CERN, Geneva, Switzerland

Controlled longitudinal emittance blow-up (from 1 eVs to 1.4 eVs) for LHC beams in the CERN PS Booster is currently achievied using sinusoidal phase modulation of a dedicated high-harmonic RF system. In 2021, after the LHC injectors upgrade, 3 eVs should be extracted to the PS. Even if the current method may satisfy the new requirements, it relies on low-power level RF improvements. In this paper another method of blow-up was considered, that is the injection of band-limited phase noise in the main RF system (h=1), never tried in PSB but already used in CERN SPS and LHC, under different conditions (longer cycles). This technique, which lowers the peak line density and therefore the impact of intensity effects in the PSB and the PS, can also be complementary to the present method. The longitudinal space charge, dominant in the PSB, causes significant synchrotron frequency shifts with intensity, and its effect should be taken into account. Another complication arises from the interaction of the phase loop with the injected noise, since both act on the RF phase. All these elements were studied in simulations of the PSB cycle with the BLonD code, and the required blow-up was achieved.

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THPVA026

Practical Stabilisation of Transverse Collective Instabilities with Second Order Chromaticity in the LHC

octupole, damping, sextupole, impedance

4477

M. Schenk, D. Amorim, N. Biancacci, X. Buffat, L.R. Carver, R. De Maria, K.S.B. Li, E. Métral, B. Salvant
CERN, Geneva, Switzerland

The study reports on dedicated measurements made with a single nominal bunch in the LHC at 6.5 TeV. First, we show that a significant amount of second order chromaticity Q'' can be introduced in the machine in a well-controlled manner. Second, we demonstrate that the incoherent betatron tune spread from Q'' can provide beam stability through the Landau damping mechanism. This is a first step in the development of a Q'' knob to be potentially applied during regular physics operation in the LHC.

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THPVA030

Collective Effects Studies of the Double-Double Bend Achromat Cell at Diamond

impedance, storage-ring, dipole, insertion-device

4493

E. Koukovini-Platia, R. Bartolini, L.M. Bobb, R.T. Fielder
DLS, Oxfordshire, United Kingdom
R. Bartolini
JAI, Oxford, United Kingdom

One cell of the Diamond storage ring has been converted from a double bend achromat to a double-double bend achromat (DDBA). After the successful installation and beam commissioning in November 2016, beam-based studies were done to assess the effect of the new cell on the single bunch and multi-bunch instabilities both in transverse and longitudinal planes. These are compared with the impedance estimate carried out both numerically and analytically.

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THPVA037

Injection of a Self-Consistent Beam at the Spallation Neutron Source

injection, space-charge, closed-orbit, target

4516

J.A. Holmes, S.M. Cousineau, T.V. Gorlov, M.A. Plum
ORNL, Oak Ridge, Tennessee, USA

Funding: ORNL is managed by UT-Battelle, LLC, under contract DE-AC05-00OR22725 for the U.S. Department of Energy. This research was supported by the DOE Office of Science, Basic Energy Science.
We plan to demonstrate the injection of a self-consistent beam into the Spallation Neutron Source (SNS). Self-consistent beams are defined to be ellipsoidal distributions with uniform density and to retain these properties under all linear transformations. Self-consistent distributions may generate very little halo if realized in practice. Some may also be manipulated to generate flat beams. Self-consistent distributions involve very special relationships between the phase space coordinates, making them difficult to realize experimentally. One self-consistent distribution, the 2D rotating distribution, can be painted into the SNS ring, with slight modification of the lattice. However, it is unknown how robust self-consistent distributions will be under real world transport in the presence of nonlinearities and other collective effects. This paper studies these issues and the mitigation of unwanted effects by applying realistic detailed computational models to the simulation of the injection of rotating beams into SNS. The result is a feasible prescription for the injection of a rotating self-consistent distribution into the SNS ring.

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THPVA040

Magnetic Field Computation for PMTs Shielding Optimization

shielding, experiment, quadrupole, photon

4522

E. Bouquerel, O. Dorvaux, S. Kihel, M. Krauth, P. Peaupardin
IPHC, Strasbourg Cedex 2, France
C. Ciemala
IFJ-PAN, Kraków, Poland

The Photon Array for the studies of Radioactive and Ion Stable beams (PARIS) is a multidetector of clusters. Each cluster is composed of 9 units of two-shells phoswiches of LaBr3/NaI scintillators optically coupled to one photomultiplier tube. PARIS will be used in combination with the VAMOS spectrometer at GANIL. During the experiment, PMTs will be exposed to the constant magnetic fringe fields produced by a quadrupole. Magnetic shielding is essential to efficiently lower the magnetic field inside the PMTs. The design and the optimization of this shield is presented. A comparison is done between the simulated and the experimental values.

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THPVA046

Thermo Mechanical Study of the ESS DTL

DTL, quadrupole, feedback, linac

4537

P. Mereu, M. Mezzano, C. Mingioni, M. Nenni
INFN-Torino, Torino, Italy
F. Grespan, A. Palmieri, A. Pisent
INFN/LNL, Legnaro (PD), Italy

The Drift Tube Linac (DTL) of the European Spallation Source (ESS) is designed to operate at 352.2 MHz with a duty cycle of 4 % (3 ms pulse length, 14 Hz repetition period) and will accelerate a proton beam of 62.5 mA pulse peak current from 3.62 to 90 MeV. In this paper the main issues regarding the thermo-mechanical 3D details of the DTL are addressed and a Computational Fluid Dynamics (CFD) model is proposed and validated against the experimental data. The results of these simulations are used to properly design the DTL cooling system.

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THPVA056

Study of Influence of Dipole and Quadrupole Power Ripple on Slow Extraction for XiPAF

extraction, quadrupole, dipole, resonance

4569

Q. Zhang, G.R. Li, Z.Y. Lin, X.W. Wang, H.J. Yao, S.X. Zheng
TUB, Beijing, People's Republic of China
X. Guan
Tsinghua University, Beijing, People's Republic of China

The 3rd resonant slow extraction and RF-Knockout technology has been adopted for XiPAF, which was designed for proton therapy and single event effects. The separatrix of stable region will fluctuate in the process of slow extraction due to power ripple, hence influence the uniform of extracted beam and the extraction efficiency. The influence of dipole and quadrupole power ripple is studied in theory and simulated by a MPI parallel multi-particle program, a method of making beam less sensitive to power ripple is discussed and verified by simulation.

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THPVA061

Study of the Cooling and Vacuum Systems of a Miniature 12 MeV Race-Track Microtron

vacuum, linac, ion, microtron

4582

Yu.A. Kubyshin, X. Escaler, A. Viladomiu
UPC, Barcelona, Spain
V.I. Shvedunov
SINP MSU, Moscow, Russia

With the aim of optimization, numerical simulations of the cooling and vacuum systems of a compact 12 MeV race-track microtron (RTM) which is under construction at the Technical University of Catalonia have been carried out. The hydraulic and thermal performance of the cooling system for various flow rates has been studied using the Computational Fluid Dynamics (CFD) software. A CFD model, previously validated with experimental pressure loss results, has permitted to simulate the cooling fluid temperature, inner wall temperatures and heat trans-fer coefficients at different sections of the RTM accelerating structure. Conclusions concerning the current design and its possible optimization are discussed. Simulations of the RTM high vacuum conditions have been performed using the Monte-Carlo simulation package Molflow+. The pressure in the vacuum chamber, pumping tube conductance and maximum allowed throughput have been calculated. Also results of the vacuum chamber pumping out sessions are reported.

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THPVA062

Fabrication and Tests of a RF Cavity for a Novel Compact Superconducting Cyclotron for Radioisotope Production

cavity, cyclotron, vacuum, pick-up

4585

D. Gavela, J. Calero, L. García-Tabarés, P. Gómez, D. López, D. Obradors-Campos, C. Oliver, J.M. Pérez Morales, I. Podadera, F. Toral
CIEMAT, Madrid, Spain
B. Bravo, R. Fos, J.R. Ocampo, F. Pérez, A. Salom, P. Solans
ALBA-CELLS Synchrotron, Cerdanyola del Vallès, Spain

Funding: Work partially funded by CDTI and supported by the Spanish Ministry of Economy and Competitiveness, under project AMIT, within the subprogram CEN-20101014
The AMIT cyclotron will be a 8.5 MeV, 10 microAmp, CW, H⁻ accelerator for radioisotope production, including a superconducting, weak focusing, 4 T magnet, allowing for a low extraction radius and a compact design. The cavity is a 60 MHz, quarter wave resonator powered by a modular 8 kW solid state amplifier. The design of the cavity dealed with challenging requirements: high electric fields required by a high voltage (60 kV) on a small gap, a small aperture of the magnet leading to high capacitances and thermal losses and a requirement for a low overall size of the cavity. The fabrication process included high precision machining, soft soldering, laser welding and careful metrologies, which are described together with other technical and practical aspects. The low power tests showed a good agreement with the simulations. The conditioning of the cavity was performed with a 1.1 T magnetic field applied on the central region. It was successfully finished regarding to maximum voltage reached, power losses and temperatures. The cavity was also tested at high power with a constant hydrogen flow injected in the central region (as expected in the cyclotron) with success.

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THPVA065

Working Concept of 12.5 kW Tuning Dump at ESS

linac, proton, target, neutron

4591

Y. Lee, M. Eshraqi, S. Ghatnekar Nilsson, Y.I. Levinsen, R. Miyamoto, S. Molloy, M. Möller, A. Olsson, T.J. Shea, C.A. Thomas, M. Wilborgsson
ESS, Lund, Sweden
F. Sordo
ESS Bilbao, Zamudio, Spain

The linac system at the European Spallation Source (ESS) will deliver 2~GeV protons at 5~MW beam power. The accelerated protons from the linac will be transported to the rotating tungsten target by two bending magnets. A tuning beam dump will be provided at the end of the linac, downstream of the first bending magnet. This tuning dump shall be able to handle at least 12.5 kW of beam power. In this paper, we present the working concept of the tuning dump. The impact of the proton beam induced material damage on the operational loads and service lifetime of the tuning dump is analysed. A number of particle transport and finite-element simulations are performed for the tuning beam modes.

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THPVA085

Design and Construction of 126 MHz Capacity Loaded Aluminium Cavity Prototype

cavity, higher-order-mode, impedance, pick-up

4653

S. Ahmadiannamin, J. Rahighi, Kh.S. Sarhadi
ILSF, Tehran, Iran
F. Abbasi
Shahid Beheshti University, Tehran, Iran
M. Lamehi Rashti
IPM, Tehran, Iran

Iranian light source Facility (ILSF)isa 3 GeV Ultra low emittance synchrotron with 528 meter circumference that will be constructed in the city of Qazvin, located 150km west of Tehran. Motivated by the development of HOM damped cavity with simpler structure at 100 MHz at MAX Lab and also lower costs, 100 MHz RF system is envisaged for ILSF booster and storage ring. An RF cavity prototype was fabricated for better understandingof characteristics of capacity loaded RF cavities by practical investigation. In this paper, design and development of this prototype is presentedwith the simulation and measurement results.

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THPVA086

Beam Dynamics Studies of an Accelerating Tube for 6 MeV Electron LINAC

emittance, electron, space-charge, linac

4657

S. Zarei
Nuclear Science and Technology Research, InstituteRadiation Application School, Tehran, Iran
F. Abbasi
Shahid Beheshti University, Tehran, Iran
S. Ahmadiannamin
ILSF, Tehran, Iran
F. Ghasemi
NSTRI, Tehran, Iran
M. Lamehi
IPM, Tehran, Iran

Side coupled standing wave accelerating tubes are widely used in a low energy linear accelerator because of relatively high accelerating gradient and low sensitivity to construction tolerances. The effective interaction of particles and electromagnetic fields is important for accelerate electrons to intended energy with the greatest efficiency and beam quality output. In this paper, we present the beam dynamics of a 6 MeV Side coupled standing wave accelerating tube using a space charge tracking algorithm (ASTRA). The designed accelerating tube that feeds by a maximum power of 2.6 MW resonant at frequency of 2998.5 MHz in pi/2 mode. 37.5 percent capture efficiency, 6.82 pi-mm-mrad horizontal emittance, 6.78 pi-mm-mrad vertical emittance, 2.24 mm horizontal and vertical beam size and 1079 keV energy spread of the output beam have been determined from the results of beam dynamics studies in ASTRA

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THPVA087

Thermal and Mechanical Analysis of 3 GHz Side Coupled RF Cavity for Medical Linacs

cavity, electron, linac, operation

4660

M. Mohseni Kejani, F. Abbasi
Shahid Beheshti University, Tehran, Iran
S. Ahmadiannamin
ILSF, Tehran, Iran
F. Ghasemi
NSTRI, Tehran, Iran
S. Zarei
Nuclear Science and Technology Research, InstituteRadiation Application School, Tehran, Iran

Medical linear accelerators have wide applications for cancer treatment in the world. Side coupled RF cavities was used in this accelerators for production of X-ray in range of energies between 4 to 25 MeV. Usually, the RF source is magnetron with lower cost in comparison to klystron in this type of applications. Side coupled cavity is a biperiodic structure with sensitive performance to operational thermal and mechanical conditions. In this paper, thermal and mechanical simulations for a period of the structure are presented.

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THPVA088

DESIGN AND CONSTRUCTION OF BRAZED SIDE COUPLED CAVITY OF MEDICAL ACCELERATOR

coupling, cavity, vacuum, electron

4664

S. Ahmadiannamin, Kh.S. Sarhadi
ILSF, Tehran, Iran
F. Abbasi, M. Mohseni Kejani
Shahid Beheshti University, Tehran, Iran
M. Bahrami, M. Lamehi
IPM, Tehran, Iran
F. Ghasemi
NSTRI, Tehran, Iran
S. Zarei
Nuclear Science and Technology Research, InstituteRadiation Application School, Tehran, Iran

Two types of standing wave RF cavities are used routinely in construction of medical linear accelerators. These two types are Side coupled and on-axis coupled standing wave cavities. This selection is based on higher shunt impedance and compactness in comparison to travelling wave RF cavities. In this paper, we present the simulation, construction and measurement results of brazed section of 3 GHz side coupled RF cavity. It is the first successful experience of its kind in Iran. The obtained experiences can be used effectively for construction of side coupled thermionic RF guns and RF cavities of medical or industrial linacs.

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THPVA120

Present Status of the SC202 Superconducting Cyclotron Project

cyclotron, extraction, cavity, proton

4730

G.A. Karamysheva, S. Gurskiy, O. Karamyshev, G. Kazakova, N.A. Morozov, D.V. Popov, E.V. Samsonov, G. Shirkov, S.G. Shirkov, G.V. Trubnikov
JINR, Dubna, Moscow Region, Russia
Y.F. Bi, G. Chen, Y. Chen, K.Z. Ding, H. Feng, J. Li, Y. Song, Y.H. Xie, Q. Yang, J. Zheng
ASIPP, Hefei, People's Republic of China
V. Malinin
JINR/DLNP, Dubna, Moscow region, Russia

In 2015 the joint project with ASIPP (Hefei, China) on design and construction of superconducting proton cyclotron SC202 was started. Two copies of SC202 shall be produced, according to the Collaboration Agreement between JINR and ASIPP. One will be used for proton therapy in Hefei and the second one will be used to replace the Phasotron in the research and treatment program on proton therapy at JINR. Recent status of the SC202 superconducting cyclotron for hadron therapy design and manufacture is presented.

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THPVA123

Neutron Doses Due to Beam Losses in a Novel Concept of a Proton Therapy Gantry

neutron, proton, beam-losses, dipole

4736

V. Talanov, D.C. Kiselev, D. Meer, V. Rizzoglio, J.M. Schippers, M. Seidel, M. Wohlmuther
PSI, Villigen PSI, Switzerland

A novel design of a gantry for proton therapy is investigated in which a degrader and emittance limiting collimators are mounted on the gantry. Due to the interactions of protons in these components there will be an additional neutron dose at the location where a patient is positioned during a proton therapy. The results of numerical study of this additional dose are presented. Neutron prompt dose at the patient position is estimated through the Monte Carlo simulation using the MCNPX 2.7.0 particle transport code. Secondary neutron and photon fluxes from the distinct beam loss points are taken into consideration and the resulting dose is calculated using realistic estimates of beam losses. The dependence of the dose on the beam energy and individual impacts of each loss point on the total dose at the patient position as well as on critical beam line components are estimated and potential design constraints are discussed. It has been found that compared with a conventional gantry the expected additional dose is higher but the optimization of the beam line configuration and additional shielding shall help to reduce the dose to an acceptable value.

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THPVA124

Simulations and Measurements of Proton Beam Energy Spectrum After Energy Degradation

proton, dipole, cyclotron, superconducting-magnet

4740

A. Gerbershagen, A. Adelmann, R. Dölling, D. Meer, V. Rizzoglio, J.M. Schippers
PSI, Villigen PSI, Switzerland

At the proton therapy facility PROSCAN of the Paul Scherrer Institute the energy modulation of the cyclotron generated proton beam is performed via material insertion into the beam trajectory. The energy spectrum of the particles propagating forwards after such procedure has been simulated and measured. The current paper summarizes the results of these simulations and measurements and illustrates their significance for the future developments of a gantry for proton therapy at the Paul Scherrer Institute.

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THPVA126

Monte Carlo Simulation of Electron Beam Irradiation System for Natural Rubber Vulcanization

electron, vacuum, linac, target

4747

K. Kosaentor
IST, Chiang Mai, Thailand
E. Kongmon, S. Rimjaem, J. Saisut, C. Thongbai
Chiang Mai University, Chiang Mai, Thailand

This paper presents the results of Monte Carlo simulation of electron beam irradiation system for natural rubber vulcanization, which is underway at Chiang Mai University in Thailand. The accelerator system can produce electron beams with adjustable energy and current in the ranges of 0.5-4 MeV and 10-100 mA, respectively. The electron beam exits from vacuum environment in the accelerator to the atmospheric air through a titanium (Ti) window. The electron dose absorption in Ti window and air was calculated by using the program GEANT4. The simulation results show that 50 μm Ti foil causes the energy loss of 1 and 18% for the beam of 4.0 and 0.5 MeV, respectively. The air gap between vacuum window and rubber surface is adjustable from 180 mm to 540 mm. The total beam energy loss of around 8-17% and 1-3% from the initial energies of 0.5 and 4 MeV, respectively. The proper depth of the natural rubber for the vulcanization process is 0.13 to 1.68 cm with the surface dose of 5.32 kGy for 0.5 MeV electron beam and 3.34 kGy for 4.0 MeV electron beam at the pulse repetition rate of 200 Hz. Accordingly, the treatment time of around 10-15 second per irradiated point is required.

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THPVA129

Spatial Distributions of natU(n, f), 238U(n, g) Reaction Rates in Spallation Neutron Fields Produced by Deuterons and 12C Ions on the Massive Uranium Target

target, detector, neutron, experiment

4753

A. Zhadan, V.V. Sotnikov, V.A. Voronko
NSC/KIPT, Kharkov, Ukraine
S.I. Tyutyunnikov
JINR, Dubna, Moscow Region, Russia
P. Zhivkov
INRNE, Sofia, Bulgaria

The results of the experiments carried out within the framework of Energy and Transmutation of RAW at JINR NUCLOTRON accelerator are presented. The target assembly QUINTA consisting of 512 kg natural uranium was irradiated by deuteron and carbon beams with energies 1, 2, 4 and 8 GeV (deuterons), 24 and 48 GeV (carbon). Spatial distribution and total number of capture reaction and fission reaction rates was obtained using the activation technique. The integral number of fissions reactions in the volume of uranium target remains approximately constant within our statistical errors for 1, 2, 4 and 8 GeV deuteron beams and for 24 and 48 GeV carbon beams (per one primary particle and per 1 GeV of beam energy). For the integral number of capture reactions with deuteron beams we have seen maximum at 2 GeV. Some of the obtained experimental data was analyzed using the MCNPX transport code. For spatial distribution of reaction rates in case of 4 and 8 GeV deuteron beams we have seen a discrepancy between the experimental and calculated values in backward direction.

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THPVA131

Biological Effectiveness of Proton and Ion Beam Therapy: Studies Using G4-DNA

proton, ion, target, experiment

4761

R.J. Barlow
University of Huddersfield, Huddersfield, United Kingdom
P. Thongjerm
IIAA, Huddersfield, United Kingdom

We have used the Geant4-DNA program to investigate on a radiobiological level the interaction of various types of particles within cells, to identify relationships between irradiation and damage to DNA, leading to cell death. Although the physical attributes of particle therapy clearly hold a benefit over conventional radiotherapy, the biological effects hold uncertainties, and modelling the way particles interact with tissue on a cellular level can reduce these. The understanding of the energy deposition pattern along the particle track and consequent probabilities of producing DNA cluster breaks enables us to predict the effects of a particle beam on a microscopic level, which can aid treatment planning.

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THPVA132

A Study of Potential Accelerator Production of Radioisotopes for Both Diagnostics and Therapy

proton, target, diagnostics, site

4765

N. Ratcliffe, T.R. Edgecock
University of Huddersfield, Huddersfield, United Kingdom

There is currently much interest in accelerator based replacements for radioisotope production. The primary focus is the use of compact low energy (<30MeV) proton accelerators that can provide local on-site production of short lived isotopes and as a replacement for the current reactor production of important isotopes such as Ga-68. As part of a study into the viability of this production method this work undertakes a benchmarking study the GEANT4 code using the new low energy data-driven physics list QGSP_BIC_AllHP for the production of significant diagnostic and therapy isotopes such as F-18 and Ga-68. results from these simulations will be compared to experimental cross-sections and other codes to determine reliability before being used to further asses the activity producible using these reactions.

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THPVA134

Coupled Longitudinal and Transverse Beam Dynamics Studies for Hadron Therapy Linacs

proton, cyclotron, linac, cavity

4772

R. Apsimon, G. Burt, S. Pitman
Cockcroft Institute, Lancaster University, Lancaster, United Kingdom
A.F. Green, H.L. Owen
UMAN, Manchester, United Kingdom

Precise proton therapy planning can be assisted by augmenting conventional medical imaging techniques with proton computed tomography (pCT). For adults this requires an incident proton energy up to at least 330 MeV, an energy not readily accessible using cyclotrons. We are presently constructing a prototype of the ProBE 54 MV/m 3GHz post-cyclotron booster linac as a compact method to achieve 330 MeV in the context of the Christie Hospital proton therapy centre, to be tested in the research room there. In this paper, we present beam dynamics studies and tracking simulations of proton beams through the booster region. The longitudinal and transverse particle transmission is calculated from tracking simulations and compared to theoretical models to help understand how best to optimise the optics design through the ProBE region.

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THPVA137

A Monte Carlo Approach to Imaging and Dose Simulations in Realistic Phantoms Using Compact X-Ray Source

photon, electron, detector, radiation

4783

E. Skordis, C.P. Welsch
The University of Liverpool, Liverpool, United Kingdom
E. Skordis, V. Vlachoudis
CERN, Geneva, Switzerland
C.P. Welsch
Cockcroft Institute, Warrington, Cheshire, United Kingdom

X-ray emitters are amongst the most widely used tools in medicine. Based on compact electron beams, they are utilised for a range of applications, including medical imaging and cancer treatment. The optimisation of a specific X-ray source relies on detailed simulation studies into the achievable resolution and intensity distribution. Monte Carlo (MC) codes are widely used in the medical community for dose estimation to patients and the environment. They are also ideally suited for simulating 3D intensity distributions in realistic environments. This demands accurate and reliable physical models capable of handling all components of the expected radiation field. In this paper the capabilities of the FLUKA MC code to simulate complex X-ray sources are presented. Advanced phantoms, based on imported DICOM format, are used to evaluate the dose to relevant areas, including the patient, individual organs and the treatment room. It is also shown how they can provide a good basis to reproduce radiography images by scoring photon fluencies.

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THPVA139

Relative Insensitivity to Inhomogeneities on Very High Energy Electron Dose Distributions

electron, experiment, radiation, photon

4791

A. Lagzda, R.M. Jones
UMAN, Manchester, United Kingdom
D. Angal-Kalinin, J.K. Jones
STFC/DL/ASTeC, Daresbury, Warrington, Cheshire, United Kingdom
K. Kirkby
The Christie NHS Foundation Trust, Manchester, United Kingdom

Funding: Science and Technology Facilities Council, United Kingdom Cockroft Institute, United Kingdom Christie Hospital, Manchester, United Kingdom
We investigated the effects of heterogeneous regions on dose deposition of very high-energy electrons (VHEE) using both Geant4 simulations and experiments performed at the CALIFES facility at CERN. Small air and acetal plastic (bone equivalent) cavities were embedded in a water phantom and irradiated with a 197 MeV electron beam. Experimentally determined transverse dose profiles were acquired using radiation sensitive EBT3 Gafchromic films embedded in the water phantom at various depths. EBT3 Gafchromic films were found to be a suitable dosimeter for relative dose dosimetry of VHEE beams. Simulated and measured results were found to be consistent with each other and the largest discrepancy was found to be no more than 5%. Dose profiles of VHEE beams were found to be relatively insensitive to embedded high and low density geometries.

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THPVA143

Beam-Breakup Studies for the 4-Pass Cornell-Brookhaven Energy Recovery LINAC Test Accelerator

HOM, lattice, cavity, dipole

4801

W. Lou, J.A. Crittenden, G.H. Hoffstaetter
Cornell University (CLASSE), Cornell Laboratory for Accelerator-Based Sciences and Education, Ithaca, New York, USA

Cornell University and Brookhaven National Laboratory are currently designing the Cornell-BNL ERL Test Accelerator (CBETA). To be built at Cornell's Wilson Lab, CBETA utilizes the existing ERL injector and main linac cryomodule (MLC). As the electron bunches pass through the MLC cavities, higher order modes (HOMs) are excited. The recirculating bunches interact with the HOMs, which can give rise to beam-breakup instability (BBU). Here we present simulation results on how BBU limits the maximum achievable current, and potential ways to improve the threshold current.

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reference for this paper ※ https://doi.org/10.18429/JACoW-IPAC2017-THPVA143

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THPVA146

Robust Linac Platform for Wide Replacement of Radioactive Sources

vacuum, linac, impedance, coupling

4805

A.V. Smirnov, M.A. Harrison, A.Y. Murokh, A.Yu. Smirnov
RadiaBeam Systems, Santa Monica, California, USA
R.B. Agustsson, S. Boucher, T.J. Campese, J.J. Hartzell, K.J. Hoyt
RadiaBeam, Santa Monica, California, USA
E.A. Savin
MEPhI, Moscow, Russia

Funding: This work was supported by the U.S. Department of Energy (awards No. DE-SC-FOA-0011370).
To improve public security and prevent the diversion of radioactive material for Radiation Dispersion Devices, development of an inexpensive, portable, easy-to-manufacture linac system is very important. Tubular structure with parallel pairs of rods crossed at 90 degrees suggests as high as 36% inter-cell coupling due to inherent compensation along with still substantial shunt impedance. Simultaneously it offers simplified brazing process and may dramatically simplify tuning of the entire structure. A novel design of a multi-cell, single-section, X-band structure for replacement of Ir192 source is presented.

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reference for this paper ※ https://doi.org/10.18429/JACoW-IPAC2017-THPVA146

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THPVA151

Halbach Magnets for CBETA and eRHIC

permanent-magnet, electron, proton, quadrupole

4814

H. Witte, J.S. Berg, B. Parker
BNL, Upton, Long Island, New York, USA

Funding: Work supported by Brookhaven Science Associates, LLC under Contract No. DE-AC02-98CH10886 with the U.S. Department of Energy.
At Brookhaven National Laboratory two design efforts are underway: eRHIC and CBETA. eRHIC is a proposed upgrade to the existing Relativistic Heavy Ion Collider (RHIC), which would allow collisions of up to 21 GeV polarized electrons with protons or heavy ions. CBETA is a 150 MeV electron accelerator, aiming to demonstrate essential technology necessary for eRHIC. Both machines employ FFAG arcs and are designated to use permanent magnet material for the required quadrupole magnets. One proposed design is a Halbach magnet; this paper investigates the feasibility of this approach.

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reference for this paper ※ https://doi.org/10.18429/JACoW-IPAC2017-THPVA151

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