Keyword: wakefield
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MOXPLM2 From Dreams to Reality: Prospects for Applying Advanced Accelerator Technology to Next Generation Scientific User Facilities plasma, electron, laser, acceleration 1
 
  • M. Ferrario
    INFN/LNF, Frascati, Italy
  • R.W. Aßmann
    DESY, Hamburg, Germany
  
  Recent years have seen spectacular progress in the development of innovative acceleration methods that are not based on traditional RF accelerating structures. These novel developments are at the interface of laser, plasma and accelerator physics and may potentially lead to much more compact and economical accelerator facilities. While primarily focusing on the ability to accelerate charged particles with much larger gradients than traditional RF, these new techniques have yet to demonstrate comparable performances to RF in terms of both beam parameters or reproducibility. To guide the developments beyond the necessary basic R&D and concept validations, a common understanding and definition of required performance and beam parameters for an operational user facility is now needed. These innovative user facilities can include "table-top" light sources, medical accelerators, industrial accelerators or even high-energy colliders. The talk will review the most promising developments in new acceleration methods, it will present the status of ongoing projects including the EU project EuPRAXIA and will identify the set of required specifications for the application under consideration.  
slides icon Slides MOXPLM2 [16.331 MB]  
DOI • reference for this paper ※ https://doi.org/10.18429/JACoW-IPAC2019-MOXPLM2  
About • paper received ※ 19 May 2019       paper accepted ※ 16 June 2019       issue date ※ 21 June 2019  
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MOPGW001 Design Review of Bellows RF-Shielding Types and New Concepts for Sirius shielding, storage-ring, HOM, impedance 53
 
  • H.O.C. Duarte, P.P.S. Freitas, A.R.D. Rodrigues, R.M. Seraphim, T.M. da Rocha
    LNLS, Campinas, Brazil
  
  Large amounts of bellows in an accelerator justify the importance of simplifying the machining and assembling processes of their RF shield. Such quantity also makes this component one of the main contributors for a machine impedance budget. On the other hand, low impedance designs tend to complicate the mechanical aspects. Applied to Sirius round vacuum chamber of 24 mm inner diameter, the omega-strip and comb-type bellows concepts are compared with new proposed designs. In such comparison, the aforementioned aspects, wakefield losses and prototyping experiences are presented in this work.  
DOI • reference for this paper ※ https://doi.org/10.18429/JACoW-IPAC2019-MOPGW001  
About • paper received ※ 16 May 2019       paper accepted ※ 20 May 2019       issue date ※ 21 June 2019  
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MOPGW038 Collimator’s Impact Into the Transverse Emittance Growth at KEK Compact ERL emittance, simulation, operation, FEL 174
 
  • O.A. Tanaka, T. Miyajima, N. Nakamura, T. Obina, M. Shimada, Y. Tanimoto
    KEK, Ibaraki, Japan
  
  In high-intensity particle accelerators, unwanted trans-verse and longitudinal wakefields arise when the high-charge particle beam passes through the narrow chambers or locations with small transverse apertures, such as collimator jaws. Transverse wakefields impose a transverse kicks to the beam, changing its shape, and leading to the growth of the transverse emittance. Longitudinal wakes cause the beam energy losses, heating of the narrow chambers etc. In the present study we investigated the collimator’s impact to the beam. Thus, we evaluated the collimator’s wakefields through the CST simulations. We estimated the corresponding transverse kicks and longitudinal wakes. In the summary simulation results were cross-checked with correspondent analytical expressions.  
DOI • reference for this paper ※ https://doi.org/10.18429/JACoW-IPAC2019-MOPGW038  
About • paper received ※ 15 May 2019       paper accepted ※ 21 May 2019       issue date ※ 21 June 2019  
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MOPGW064 On Wakefield in Dielectric Waveguide with Shallow Corrugation of Metallic Wall GUI, radiation, ECR, impedance 237
 
  • A.V. Tyukhtin, E.R. Akhmatova, T.Yu. Alekhina, S.N. Galyamin, V.V. Vorobev
    Saint Petersburg State University, Saint Petersburg, Russia
  
  Funding: This work was supported by the Russian Science Foundation (Grant # 18-72-10137).
Bunch radiation in periodical waveguides was mainly analyzed for situations when wavelengths are comparable to the structure period (Smith-Purcell emission). However, it is also of interest to study the "long-wave radiation" with wavelengths which are much larger than the structure period*,**. In such situation, the exact boundary conditions on the complicated periodic surface can be replaced with the equivalent boundary conditions (EBC) which must be fulfilled on the smooth surface. Earlier we considered with this approach radiation of the bunch moving along the axis of circular vacuum corrugated waveguide**. Comparison of analytical results with COMSOL simulations showed high accuracy of the EBC method. Here we analyze an analogous problem for the waveguide with corrugated wall and dielectric filling under condition that Cherenkov effect takes place in the dielectric. Due to this fact the radiation differs radically from that in the vacuum waveguide. At the same time, the radiation has essential differences from the one in the usual dielectric waveguide. The radiation properties in the waveguide under consideration and its differences from the radiation in the waveguide with smooth wall are analyzed.
* G. Stupakov, K. Bane, Phys. Rev. ST-AB, 15 (2012) 124401.
** A.V. Tyukhtin et al, J. of Instrumentation, 13 (2018) C04009.
 
DOI • reference for this paper ※ https://doi.org/10.18429/JACoW-IPAC2019-MOPGW064  
About • paper received ※ 15 May 2019       paper accepted ※ 20 May 2019       issue date ※ 21 June 2019  
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MOPGW071 Resistive Wall Effects in the CLIC Beam Delivery System luminosity, collider, vacuum, feedback 258
 
  • D. Arominski, A. Latina, D. Schulte
    CERN, Meyrin, Switzerland
  
  Resistive wall wakefields are an important issue to study for future linear colliders. Wakefields in the Beam Delivery System (BDS) might cause severe multi-bunch effects, leading to beam quality and luminosity losses. The resistive wall effects depend on the beam pipe apertures and materials, which are optimised to limit the impact on the beam. This paper presents a study of this problem for the 380 GeV and 3 TeV beam parameters and optics of the Compact Linear Collider’s BDS. First, the optimisation of the beam pipe apertures to limit the impact of resistive wall effect on the beam quality is shown, then the luminosity and its quality are presented. Finally, the proposed design parameters are discussed.  
DOI • reference for this paper ※ https://doi.org/10.18429/JACoW-IPAC2019-MOPGW071  
About • paper received ※ 16 May 2019       paper accepted ※ 20 May 2019       issue date ※ 21 June 2019  
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MOPGW073 Beam Manipulation Using Self-Induced Fields at the SwissFEL Injector FEL, simulation, electron, experiment 266
 
  • S. Bettoni, P. Craievich, E. Ferrari, R. Ganter, F. Marcellini, E. Prat, S. Reiche
    PSI, Villigen PSI, Switzerland
  • A.A. Lutman
    SLAC, Menlo Park, California, USA
  • G. Penco
    Elettra-Sincrotrone Trieste S.C.p.A., Basovizza, Italy
  
  In the past years wakefield sources have been used to manipulate electron beams in accelerators. We recently installed corrugated structures for a total length of 2~m at the SwissFEL injector to test novel schemes for beam manipulations. We present simulations and early experimental results. We compare the model predictions with the measured data for the bunch energy losses and the kick factor, and show early results for the longitudinal phase space linearization and the production of current spikes.  
DOI • reference for this paper ※ https://doi.org/10.18429/JACoW-IPAC2019-MOPGW073  
About • paper received ※ 09 May 2019       paper accepted ※ 20 May 2019       issue date ※ 21 June 2019  
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MOPGW085 Intensity Dependent Effects in the ILC BDS luminosity, collider, simulation, linear-collider 305
 
  • P. Korysko, A. Latina
    CERN, Geneva, Switzerland
  • P. Burrows
    Oxford University, Physics Department, Oxford, Oxon, United Kingdom
  
  The International Linear Collider (ILC) is an electron-positron collider being considered for the post-LHC era. Its Beam Delivery System (BDS) receives the beam from the main linac. This beam is then focused to the nanometer scale after going through collimators, beam diagnostic systems, strong magnets, etc. Effects such as wakefields due to resistive-wall, BPMs and collimators make the system very sensitive to the beam intensity. Understanding these effects is crucial in order to demonstrate that the nominal beam size at the Interaction Point (IP) can be reached in realistic scenarios. In this paper, results of the intensity dependence effects in the ILC BDS, simulated with PLACET, are presented.  
DOI • reference for this paper ※ https://doi.org/10.18429/JACoW-IPAC2019-MOPGW085  
About • paper received ※ 23 April 2019       paper accepted ※ 20 May 2019       issue date ※ 21 June 2019  
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MOPGW086 Intensity Dependent Effects at ATF2, KEK simulation, collider, linear-collider, electron 308
 
  • P. Korysko, A. Latina
    CERN, Geneva, Switzerland
  • P. Burrows
    Oxford University, Physics Department, Oxford, Oxon, United Kingdom
  • A. Faus-Golfe
    LAL, Orsay, France
  • K. Kubo, T. Okugi
    KEK, Ibaraki, Japan
  
  The Accelerator Test Facility 2 (ATF2) at KEK is a prototype for the Final Focus Systems of the future e+e− linear colliders, the International Linear Collider (ILC) and the Compact Linear Collider (CLIC). In this paper both simulation and experimental results are presented with special emphasis on intensity-dependent effects. The importance of these effects is shown using the PLACET code and realistic ATF2 machine simulations (including beam jitter, misalignment, wakefield, Beam Based Alignment (BBA) correction, …). The latest experimental results are also presented, in particular the impact of the beam intensity on the beam size at the IP.  
DOI • reference for this paper ※ https://doi.org/10.18429/JACoW-IPAC2019-MOPGW086  
About • paper received ※ 23 April 2019       paper accepted ※ 20 May 2019       issue date ※ 21 June 2019  
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MOPMP018 Beam-Based Beamline Element Alignment for the Main Linac of the 380 GeV Stage of CLIC emittance, linac, alignment, collider 465
 
  • N. Blaskovic Kraljevic, D. Schulte
    CERN, Meyrin, Switzerland
  
  The extremely small vertical beam size required at the interaction point of future linear colliders, such as the Compact Linear Collider (CLIC), calls for a very small vertical emittance. The strong wakefields in the high frequency 12 GHz CLIC accelerating structures set tight tolerances on the alignment of the main linac’s beamline elements and on the correction of the beam orbit through them in order to mantain a small emittance growth. This paper presents the emittance growth due to each type of beamline element misalignment in the designed 380 GeV centre-of-mass energy first-stage of CLIC, and the emittance growth following a series of beam-based alignment (BBA) procedures. The BBA techniques used are one-to-one steering, followed by dispersion free steering and finally accelerating structure alignment using wakefield monitors.  
DOI • reference for this paper ※ https://doi.org/10.18429/JACoW-IPAC2019-MOPMP018  
About • paper received ※ 13 May 2019       paper accepted ※ 20 May 2019       issue date ※ 21 June 2019  
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MOPRB087 Proposal for a High Transformer Ratio CW Dielectric Accelerator electron, SRF, experiment, operation 773
 
  • V. Litvinenko
    Stony Brook University, Stony Brook, USA
  • J.C. Brutus, Y.C. Jing, I. Pinayev, G. Wang
    BNL, Upton, Long Island, New York, USA
  • M.E. Conde, C.-J. Jing, J.G. Power
    ANL, Argonne, Illinois, USA
  • A. Kanareykin
    Euclid Beamlabs LLC, Bolingbrook, USA
  • N. Vafaei-Najafabadi
    UCLA, Los Angeles, California, USA
  
  Advanced CW accelerators are one of high priority directions identified by Advanced Accelerator Concepts Research Roadmap Workshop Report *. High transformer ratio of beam-driven accelerators is critically important for cost-effective FEL systems. We present a proposed experiment for demonstrating a high transformer ratio CW dielectric accelerator using operational SRF accelerator built for Coherent electron Cooling experiment. This accelerator operates with CW electron beam comprised of 78 kHz train of electron bunches. Electron bunches with controllable longitudinal and charge up to 10 nC per bunch are generated in 1.25 MV SRF photo-electron gun. This bunches are ballistically compressed to duration of 10-to-30 psec and accelerated to 15 MeV in SRF linac**. Such bunches would be excellent drivers of high-transformer ratio DWA accelerators. In this paper we present expected performance of proposed CW DWA accelerator.
*Advanced Accelerator Concepts Research Roadmap Workshop Report, 2016,
*V.N. Litvinenko et al., In proc.of FEL’17, Santa Fe, NM, USA, August 20-25, 2017, p. 132 		 
DOI • reference for this paper ※ https://doi.org/10.18429/JACoW-IPAC2019-MOPRB087  
About • paper received ※ 19 May 2019       paper accepted ※ 22 May 2019       issue date ※ 21 June 2019  
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MOPTS067 The Progress in Physics Design of HEPS LINAC linac, bunching, electron, emittance 1008
 
  • C. Meng, D.Y. He, X. He, J.Y. Li, Y.M. Peng, S.C. Wang, O. Xiao, J.R. Zhang, S.P. Zhang
    IHEP, Beijing, People’s Republic of China
  
  The High Energy Photon Source (HEPS) is a 6-GeV, ultralow-emittance light source to be built in China. The injector is composed of a 500-MeV Linac and a full energy booster. According to the study and com-missioning consideration of on-axis swap-out injec-tion system, a high bunch charge injector is desirable and a Linac that can provide 7nC per bunch electron beam to booster is needed. This paper present different bunching system schemes and the performance of different schemes are discussed.  
DOI • reference for this paper ※ https://doi.org/10.18429/JACoW-IPAC2019-MOPTS067  
About • paper received ※ 14 May 2019       paper accepted ※ 17 May 2019       issue date ※ 21 June 2019  
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TUZZPLS3 New Method of Calculation of the Wake due to Radiation and Space Charge Forces in Relativistic Beams radiation, electron, space-charge, synchrotron-radiation 1223
 
  • G. Stupakov
    SLAC, Menlo Park, California, USA
  
  Funding: This work was supported by the Department of Energy, Contract No. DE-AC02-76SF00515.
Radiation reaction force in a relativistic beam, also known as a CSR wakefield, is often computed using a 1D model of a line charge beam. While this model can serve as a useful tool for a quick calculation, in some cases, it may not be sufficiently accurate. In particular, this model misses the so-called compression effects associated with the change of the electromagnetic energy when the beam is compressed longitudinally or transversely. The existing 3D simulation codes that take this effect into account are often slow and are not easy to use. In this work, we propose a new approach to the calculations of radiation and space charge longitudinal forces based on the use of the integrals for the retarded potentials. Our main result expresses the rate of change of particles energy through 2D (in a 2D model) or 3D integrals for a given orbit of the beam. It generalizes the 1D model and includes the transient effects of at the entrance and the exit from the magnet. For a given beam line with known magnetic lattice, and a known distribution function of the beam, the calculation reduces to taking 2D or 3D integrals along the orbit. 		 
slides icon Slides TUZZPLS3 [2.080 MB]  
DOI • reference for this paper ※ https://doi.org/10.18429/JACoW-IPAC2019-TUZZPLS3  
About • paper received ※ 29 April 2019       paper accepted ※ 22 May 2019       issue date ※ 21 June 2019  
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TUPMP041 Preliminary Design of RF-Shielded Bellows interface, vacuum, shielding, experiment 1341
 
  • Y.T. Huang, C.K. Chan, C.-C. Chang, C.M. Cheng, P.J. Chou, Y.C. Yang
    NSRRC, Hsinchu, Taiwan
  
  A new design of RF-shielded bellows is proposed for the TPS to alleviate wake field effects and Joule heating resulting from contact resistance at the contact interface of sliding two dissimilar metals. Most efforts are put into controlling corrosion which is regarded as the main cause of electrical contact degradation. Rh-Au is chosen as a mating interface because they are stable under high temperature condition. Experimental tests are made to find an effective plating thickness of Rh and Au and to determine a suitable normal load applicable on the Rh-Au interface. A preliminary design of RF-shielded bellows that can sustain thousands of cycles during their lifetime is under testing.  
DOI • reference for this paper ※ https://doi.org/10.18429/JACoW-IPAC2019-TUPMP041  
About • paper received ※ 06 May 2019       paper accepted ※ 22 May 2019       issue date ※ 21 June 2019  
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TUPRB108 Mechanical Design of a Dielectric Wakefield Dechirper System for CLARA vacuum, FEL, electron, alignment 1912
 
  • M. Colling, D.J. Dunning, B.D. Fell, T.H. Pacey, Y.M. Saveliev
    STFC/DL/ASTeC, Daresbury, Warrington, Cheshire, United Kingdom
  
  STFC Daresbury Laboratory are developing a compact electron beam energy dechirper system, based on dielectric wakefield structure, for the on-site electron accelerator CLARA (Compact Linear Accelerator for Research and Applications). CLARA will be an experimental free electron laser (FEL) facility operating at 250MeV and will be a test bed for a variety of novel FEL schemes. The dechirper dielectric quartz plates will induce wakefields within the structure which can remove the beam chirp that is initially introduced to compress the electron bunch longitudinally. Removing or adjusting the amount of chirp enables researchers to reduce or adjust the bunch energy/momentum spread, expanding the FEL capabilities. The attachment and alignment of the quartz plates present numerous mechanical design challenges that require high precision manufacturing and quartz plate positioning via fiducialisation. This paper will review the dechirper specifications, the chosen design solutions, measured mechanical performance, and the expected effect of the dechirper on CLARA FEL operation.  
DOI • reference for this paper ※ https://doi.org/10.18429/JACoW-IPAC2019-TUPRB108  
About • paper received ※ 13 May 2019       paper accepted ※ 22 May 2019       issue date ※ 21 June 2019  
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TUPTS090 Experimental Results of Dense Array Diamond Field Emitters in RF Gun cathode, gun, experiment, solenoid 2134
 
  • K.E. Nichols, H.L. Andrews, D. Kim, E.I. Simakov
    LANL, Los Alamos, New Mexico, USA
  • S.P. Antipov
    Euclid Beamlabs LLC, Bolingbrook, USA
  • G. Chen
    IIT, Chicago, Illinois, USA
  • M.E. Conde, D.S. Doran, G. Ha, W. Liu, J.F. Power, J.H. Shao, C. Whiteford, E.E. Wisniewski
    ANL, Argonne, Illinois, USA
  
  We present experimental emission results from arrays of diamond field emitter tips operating in an RF gun at the Argonne Cathode Test-stand. Results from various arrays will be presented with different spacing between array elements. Very high charge densities were produced at various field gradients. The maximum field gradient for a particular geometry was discovered and break-down effects will be presented. Cathode lifetime was preliminarily studied. Further experiments are being planned and work on the cathode design optimization to produce higher quality beams will be discussed.  
DOI • reference for this paper ※ https://doi.org/10.18429/JACoW-IPAC2019-TUPTS090  
About • paper received ※ 15 May 2019       paper accepted ※ 22 May 2019       issue date ※ 21 June 2019  
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WEYPLS1 Building the Impedance Model of a Real Machine impedance, simulation, coupling, cavity 2249
 
  • B. Salvant, D. Amorim, S.A. Antipov, S. Arsenyev, M.S. Beck, N. Biancacci, O.S. Brüning, J.V. Campelo, E. Carideo, F. Caspers, A. Farricker, A. Grudiev, T. Kaltenbacher, E. Koukovini-Platia, P. Kramer, A. Lasheen, M. Migliorati, N. Mounet, E. Métral, N. Nasr Esfahani, S. Persichelli, B.K. Popovic, T.L. Rijoff, G. Rumolo, E.N. Shaposhnikova, V.G. Vaccaro, C. Vollinger, N. Wang, C. Zannini, B. Zotter
    CERN, Geneva, Switzerland
  • D. Amorim
    Grenoble-INP Phelma, Grenoble, France
  • T. Dalascu
    EPFL, Lausanne, Switzerland
  • M. Migliorati
    Sapienza University of Rome, Rome, Italy
  • R. Nagaoka
    SOLEIL, Gif-sur-Yvette, France
  • V.V. Smaluk
    BNL, Upton, Long Island, New York, USA
  • B. Spataro
    INFN/LNF, Frascati, Italy
  • N. Wang
    IHEP, Beijing, People’s Republic of China
  • S.M. White
    ESRF, Grenoble, France
  
  A reliable impedance model of a particle accelerator can be built by combining the beam coupling impedances of all the components. This is a necessary step to be able to evaluate the machine performance limitations, identify the main contributors in case an impedance reduction is required, and study the interaction with other mechanisms such as optics nonlinearities, transverse damper, noise, space charge, electron cloud, beam-beam (in a collider). The main phases to create a realistic impedance model, and verify it experimentally, will be reviewed, highlighting the main challenges. Some examples will be presented revealing the levels of precision of machine impedance models that have been achieved.  
slides icon Slides WEYPLS1 [5.648 MB]  
DOI • reference for this paper ※ https://doi.org/10.18429/JACoW-IPAC2019-WEYPLS1  
About • paper received ※ 10 May 2019       paper accepted ※ 23 May 2019       issue date ※ 21 June 2019  
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WEZPLS2 High Transformer Ratio Plasma Wakefield Acceleration Driven by Photocathode Laser Shaped Electron Bunches plasma, laser, acceleration, experiment 2286
 
  • G. Loisch
    DESY Zeuthen, Zeuthen, Germany
  
  Beam driven wakefield acceleration (PWFA) schemes in plasmas are among the most promising candidates for novel, compact accelerators. Several aspects of PWFA are under investigation at the Photoinjector Test facility at DESY in Zeuthen (PITZ). One of the main characteristics of these accelerators is the ratio between field strength usable for acceleration and decelerating field strength in the driver bunch, the so called transformer ratio. To reach high transformer ratios usually shaped bunches, e.g. with ramped current profiles are employed as drivers. The so-called self-modulation instability, which causes transverse modulation of a bunch longer than the plasma wavelength, is proposed as a means of supplying short driver bunches for proton-driven PWFA. This talk will give an overview on experimental results in these two aspects of PWFA at PITZ with a focus on the production of electron bunches enabling high transformer ratio acceleration by shaping the photocathode laser pulses of a photoinjector and the demonstration of high transformer ratio PWFA. Simulations and further developments on the shaping techniques, allowing highly flexible electron bunches for future plasma wakefield accelerators are also presented.  
slides icon Slides WEZPLS2 [5.172 MB]  
DOI • reference for this paper ※ https://doi.org/10.18429/JACoW-IPAC2019-WEZPLS2  
About • paper received ※ 21 May 2019       paper accepted ※ 29 May 2019       issue date ※ 21 June 2019  
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WEZZPLS3 Longitudinal-Phase-Space Manipulation for Efficient Beam-Driven Structure Wakefield Acceleration linac, electron, simulation, acceleration 2296
 
  • W.H. Tan, P. Piot
    Northern Illinois University, DeKalb, Illinois, USA
  • P. Piot
    Fermilab, Batavia, Illinois, USA
  • A. Zholents, A. Zholents
    ANL, Argonne, Illinois, USA
  
  Funding: This work is funded by the United States Department of Energy awards DE-SC0018656 with Northern Illinois University and DE-AC02-06CH11357 with Argonne National Laboratory.
Collinear beam-driven structure wakefield acceleration (SWFA) is an advanced acceleration technique that could support the compact generation of high-energy beams for future multi-user x-ray free-electron-laser facilities*. Producing an ideal shaped drive beam through phase space manipulation is crucial for an efficient SWFA. Controlling the final longitudinal-phase space of the drive beam necessitate staged beam manipulations during acceleration. This paper describes the preliminary design of an accelerator beamline capable of producing drive beam with tailored current distribution and longitudinal-phase-space correlation. The proposed design is based on simple analytical models combined in a 1-D longitudinal beam-dynamics simulation tracking program supporting forward and backward (time reversal) tracking.
* A. Zholents, et al., Dielectric wakefield accelerator to drive the future FEL light source 		 
slides icon Slides WEZZPLS3 [2.869 MB]  
DOI • reference for this paper ※ https://doi.org/10.18429/JACoW-IPAC2019-WEZZPLS3  
About • paper received ※ 14 May 2019       paper accepted ※ 20 May 2019       issue date ※ 21 June 2019  
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WEPRB034 Study on the Design of the X-band Waveguide-damped Structure damping, GUI, HOM, simulation 2886
 
  • X.X. Huang, W. Fang, Z.T. Zhao
    SSRF, Shanghai, People’s Republic of China
  • A. Grudiev
    CERN, Meyrin, Switzerland
  
  The design of waveguide-damped structure is optimized to reduce the magnitudes of surface electromagnetic fields and strongly suppress long-range transverse wakefields of the 380 GeV Compact Linear Collider facility currently under study. The optimization is mainly discussed with the elliptical shape of the iris, the wall shape of the damping waveguides, the position of the high-order-mode damping loads and the widths of the waveguide openings of the entire sequence of damping waveguides.  
DOI • reference for this paper ※ https://doi.org/10.18429/JACoW-IPAC2019-WEPRB034  
About • paper received ※ 13 May 2019       paper accepted ※ 22 May 2019       issue date ※ 21 June 2019  
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WEPRB043 Wakefield Suppression in the Main LINAC of the Klystron-Based First Stage of CLIC at 380 GeV HOM, GUI, damping, linac 2899
 
  • J.Y. Liu, H.B. Chen, J. Shi, H. Zha
    TUB, Beijing, People’s Republic of China
  • A. Grudiev
    CERN, Meyrin, Switzerland
  
  An alternative klystron-based scenario for the first stage of Compact Linear Collider (CLIC) at 380 GeV centre-of-mass energy was proposed. To preserve the beam stability and luminosity of CLIC, the beam-induced transverse long-range wakefield in main linac must be suppressed to an acceptable value. The design of klystron-based accelerating structure is based on waveguide damping structure (WDS). The high-order modes (HOMs) propagating into four waveguides are absorbed by HOM damping loads. In this paper, the wakefield suppression in CLIC-K based on GdfidL code simulations are presented.  
DOI • reference for this paper ※ https://doi.org/10.18429/JACoW-IPAC2019-WEPRB043  
About • paper received ※ 14 May 2019       paper accepted ※ 22 May 2019       issue date ※ 21 June 2019  
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WEPRB068 Ka-Band Linearizer Studies for a Compact Light Source klystron, impedance, FEL, flattop 2976
 
  • A. Castilla, G. Burt, W.L. Millar
    Cockcroft Institute, Lancaster University, Lancaster, United Kingdom
  • A. Latina, X. Liu, W.L. Millar, X.W. Wu, W. Wuensch
    CERN, Geneva, Switzerland
  
  Funding: This project has received funding from the European Union’s Horizon2020 research and innovation programme under grant agreement No 777431.
The CompactLight project is currently developing the design of a next generation hard X-ray FEL facility, based on high-gradient X-band (12 GHz) structures, bright electron photo-injectors, and compact short period undulators. However, to improve the brightness limitations due to the non-linear energy spread of the electron bunches, a K-band (36 GHz) linearizer is being considered to provide a harmonic compensation during the bunch compression. In this paper, we analyze the feasibility of such linearizer. 		 
DOI • reference for this paper ※ https://doi.org/10.18429/JACoW-IPAC2019-WEPRB068  
About • paper received ※ 15 May 2019       paper accepted ※ 22 May 2019       issue date ※ 21 June 2019  
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WEPRB069 Wakefield Suppression in a Manifold Damped and Detuned Structure for a 380 GeV CLIC Staged Design dipole, damping, accelerating-gradient, collider 2980
 
  • N.Y. Joshi, R.M. Jones
    UMAN, Manchester, United Kingdom
  
  The first stage of the Compact Linear Collider (CLIC) project aims to collide electrons and positrons at a 380 GeV center of mass energy. In the baseline design the main linacs for this staged approach are required to achieve a gradient of 72 MeV/m, with the surface electromagnetic fields (EM) and the transverse long-range wakefields bound by beam dynamics constraints. The baseline design utilizes heavy damping in a traveling wave (TW) structure. Here we report on an alternate design, which adopts moderate damping along with strong detuning of the individual cell frequencies. In the context of this Damped and Detuned Structure (DDS) design, we study Gaussian and hyperbolic secant dipole distributions, together with interleaving of successive structures, to effect long-range transverse wakefield suppression. Both analytic and modal summation approaches, in the quasi-coupled approximation, produce consistent results. In the optimisation scheme we opt for a dipole frequency bandwidth of 17.7 % (2.92 GHz)  
DOI • reference for this paper ※ https://doi.org/10.18429/JACoW-IPAC2019-WEPRB069  
About • paper received ※ 13 May 2019       paper accepted ※ 20 May 2019       issue date ※ 21 June 2019  
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WEPRB081 Design Study on Higher Harmonic Cavity for ALS-U cavity, impedance, higher-order-mode, simulation 3011
 
  • H.Q. Feng, K.M. Baptiste, S. De Santis, D. Li, T.H. Luo
    LBNL, Berkeley, California, USA
  • H.Q. Feng, W.-H. Huang, Z.N. Liu, C.-X. Tang
    TUB, Beijing, People’s Republic of China
  
  Funding: Director of Office of Science of the U.S. Department of Energy under Contract No. DE-AC02-05CH11231
The ALS upgrade (ALS-U) to a diffraction-limited light source [1] depends on the ability to lengthen the stored bunches to limit the emittance growth and increase the beam life time. Higher harmonic cavities (HHCs), also known as Landau cavities, have been proposed to in-crease beam lifetime and Landau damping by lengthen-ing the bunch. We present an optimized 1.5 GHz normal conducting HHC design for the ALS-U with a supercon-ducting-like geometry using multi-objective genetic algorithm (MOGA) for lower R/Q. The optimization goal is to reach the required shunt impedance while maintain-ing a relatively high Q value of the cavities. To minimize the coupled bunch instabilities, higher-order mode (HOM) of the HHC as well as corresponding impedance are explored and characterized. 		 
DOI • reference for this paper ※ https://doi.org/10.18429/JACoW-IPAC2019-WEPRB081  
About • paper received ※ 16 May 2019       paper accepted ※ 21 May 2019       issue date ※ 21 June 2019  
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WEPTS034 Generation of Sub-Femtosecond Electron Beams and Electron Bunch Trains With High Form Factor Using Wake Field Structures electron, bunching, space-charge, simulation 3174
 
  • Z. Dong, H. Chen, X.J. Deng, Y.C. Du, Z. Zhou
    TUB, Beijing, People’s Republic of China
  
  In this paper, we propose two beam manipulation methods with wakefield structures in a photo-injector. First, we propose a simple scheme to compensate non-linear effects during ballistic bunching by using a wakefield structure. Simulations have shown beams of 1 pC charge can be compressed to 1.56 fs rms, and even shorter beams (a few hundred attoseconds) can be obtained with bunch charge well below 1 pC. In the second part, a method of producing bunch trains with high form factor is proposed by using multiple wake-field structures. Simulation results have shown the production of a train with a form factor of 0.5 using a 1 nC beam at few-MeV energy.  
DOI • reference for this paper ※ https://doi.org/10.18429/JACoW-IPAC2019-WEPTS034  
About • paper received ※ 11 May 2019       paper accepted ※ 23 May 2019       issue date ※ 21 June 2019  
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WEPTS045 High-Performance Scheduling of Multi-Beam Multi-Bunch Simulations simulation, collider, site, hadron 3208
 
  • S.V. Furuseth, X. Buffat
    CERN, Geneva, Switzerland
  • S.V. Furuseth
    EPFL, Lausanne, Switzerland
  
  Coherent multi-bunch interactions through beam-beam forces or wake fields can cause severe impacts on the beams in circular colliders, if not well understood and countered for. COMBI is a parallel multiparticle tracking code developed to study such interactions. Its implementation greatly limits its efficiency when considering realistic configurations featuring effects with different computational requirements, such as the multi-bunch interaction through wake fields, beam-beam interactions, transverse feedback and lattice non-linearities. A new parallel scheduling method, pipelining the effects for each bunch, has greatly sped up the code. The new version of the code, COMBIp, is presented here.  
DOI • reference for this paper ※ https://doi.org/10.18429/JACoW-IPAC2019-WEPTS045  
About • paper received ※ 06 May 2019       paper accepted ※ 21 May 2019       issue date ※ 21 June 2019  
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WEPTS055 Energy Modulation of Electron Beam in Corrugated Dielectric Waveguide experiment, simulation, acceleration, electron 3248
 
  • A. Lyapin, S.T. Boogert, S.M. Gibson, K. Lekomtsev
    JAI, Egham, Surrey, United Kingdom
  • A. Aryshev, N. Terunuma, J. Urakawa
    KEK, Ibaraki, Japan
  • A.A. Tishchenko
    MEPhI, Moscow, Russia
  • A.A. Tishchenko
    NRC, Moscow, Russia
  
  Energy modulated electron beams have a wide range of applications in accelerator physics, for example they can serve as drivers in resonant wakefield acceleration schemes. A strong wakefield induced energy modulation can be produced using a dielectric lined waveguide, the resultant micro-bunched beam is capable of producing coherent terahertz radiation *. We report on observation of energy modulation due to self-wakefields in a few picosecond duration and ~1 nC charge electron bunches of LUCX facility at KEK. To produce the modulation, we used a corrugated dielectric waveguide with an inner radius of 2 mm and a period of corrugation of 10 mm. In this case, the period of corrugation is longer than the wavelength of the main accelerating mode. We show electromagnetic simulations of on-axis electric fields leading to an optimisation of the corrugation period allowing to enhance the accelerating/decelerating fields compared to dielectric lined waveguides with a constant inner radius.
* S. Antipov et al., Experimental observation of energy modulation in electron beams passing though terahertz dielectric wakefield structures, PRL 108, 144801 (2012). 		 
DOI • reference for this paper ※ https://doi.org/10.18429/JACoW-IPAC2019-WEPTS055  
About • paper received ※ 15 May 2019       paper accepted ※ 23 May 2019       issue date ※ 21 June 2019  
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THPGW002 A Passive Plasma Beam Dump Study with Application to EuPRAXIA plasma, simulation, electron, laser 3581
 
  • R.P. Nunes
    UFRGS, Porto Alegre, Brazil
  • A. Bonatto
    University of Manchester, Manchester, United Kingdom
  • G.X. Xia
    UMAN, Manchester, United Kingdom
  
  Funding: The author R. P. Nunes acknowledges the financial support provided by FAPERGS.
This work presents a study about a passive dumping scheme applied to the beam generated by the accelerator stage of the EuPraxia experiment. Particle-in-cell simulations have been carried out and its results are compared with analytical estimates, showing a reasonable agreement. 		 
DOI • reference for this paper ※ https://doi.org/10.18429/JACoW-IPAC2019-THPGW002  
About • paper received ※ 05 May 2019       paper accepted ※ 22 May 2019       issue date ※ 21 June 2019  
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THPGW003 Energy Loss of an Electron Beam with Gaussian Density Profile Propagating in a Passive Plasma Beam Dump plasma, electron, simulation, laser 3584
 
  • A. Bonatto
    University of Manchester, Manchester, United Kingdom
  • R.P. Nunes
    UFRGS, Porto Alegre, Brazil
  • G.X. Xia
    UMAN, Manchester, United Kingdom
  
  Funding: CNPq, and FAPERGS, from Brazil.
A semi-analytical 1D model is derived for the total energy loss of an electron beam with Gaussian density profile undergoing a passive plasma beam dump. The model is compared to a previous one, obtained for a half-sine longitudinal density profile. It is shown that both models agree if the beam density profiles are properly matched, and if their sizes are small in comparison to the length of wakefield decelerating length. The beam energy obtained from both models is compared to 1D PIC simulation results. 		 
DOI • reference for this paper ※ https://doi.org/10.18429/JACoW-IPAC2019-THPGW003  
About • paper received ※ 09 May 2019       paper accepted ※ 23 May 2019       issue date ※ 21 June 2019  
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THPGW016 Overview and Prospects of Plasma Wakefield Acceleration Experiments at PITZ plasma, electron, laser, experiment 3612
 
  • O. Lishilin, Y. Chen, J.D. Good, M. Groß, I.I. Isaev, C. Koschitzki, M. Krasilnikov, G. Loisch, D. Melkumyan, R. Niemczyk, A. Oppelt, H.J. Qian, F. Stephan
    DESY Zeuthen, Zeuthen, Germany
  • R. Brinkmann, A. Martinez de la Ossa, J. Osterhoff
    DESY, Hamburg, Germany
  • F.J. Grüner
    Center for Free-Electron Laser Science, Universität Hamburg, Hamburg, Germany
  • T.J. Mehrling, C.B. Schroeder
    LBNL, Berkeley, USA
  
  The Photo Injector Test Facility at DESY in Zeuthen (PITZ) carries out studies of beam-driven plasma wakefield acceleration (PWFA). The facility possesses a flexible photocathode laser beam shaping system and a variety of diagnostics including a high-resolution dipole spectrometer and an rf deflector which enables the observation of the longitudinal phase space of electron beams after their passage through a plasma. Two plasma sources are available: a gas discharge plasma cell and a photoionized lithium vapor plasma cell. Studies at PITZ include investigations of the self-modulation instability of long electron beams and the high transformer ratio, i.e., the ratio between the maximum accelerating field behind the drive beam and the decelerating field within the beam. This overview includes the experimental results and plans for future experiments.  
DOI • reference for this paper ※ https://doi.org/10.18429/JACoW-IPAC2019-THPGW016  
About • paper received ※ 30 April 2019       paper accepted ※ 19 May 2019       issue date ※ 21 June 2019  
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THPGW017 Self-Modulation Instability of Electron Beams in Plasma Channels of Variable Length plasma, simulation, laser, electron 3616
 
  • O. Lishilin, Y. Chen, J.D. Good, M. Groß, I.I. Isaev, C. Koschitzki, M. Krasilnikov, G. Loisch, A. Oppelt, H.J. Qian, F. Stephan
    DESY Zeuthen, Zeuthen, Germany
  • R. Brinkmann, A. Martinez de la Ossa, J. Osterhoff
    DESY, Hamburg, Germany
  • F.J. Grüner
    Center for Free-Electron Laser Science, Universität Hamburg, Hamburg, Germany
  • T.J. Mehrling, C.B. Schroeder
    LBNL, Berkeley, USA
  
  The self-modulation instability (SMI) of long (in respect to the plasma wavelength) charged particle beams passing through plasma enables the use of currently existing high energy charged particle beams as drivers for plasma wakefield accelerators. At the Photo Injector Test facility at DESY in Zeuthen (PITZ) the SMI of electron beams is studied *, **. An enhanced experimental setup includes a plasma channel of variable length which allows to investigate in details the development stages of the SMI by measuring the instability growth rate and phase velocity as a function of propagation distance in the plasma. In this contribution we present the experimental setup improvements, first measurement results and supporting beam dynamics simulations.
* M. Gross, et al., Phys. Rev. Lett., vol. 120, p. 144802, 2018.
** G. Loisch, et al., Plasma Physics and Controlled Fusion, vol. 61(4), p. 045012, 2019 		 
DOI • reference for this paper ※ https://doi.org/10.18429/JACoW-IPAC2019-THPGW017  
About • paper received ※ 11 May 2019       paper accepted ※ 23 May 2019       issue date ※ 21 June 2019  
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THPGW019 FLASHforward Findings for the EuPRAXIA Design Study and the Next-Generation of Compact Accelerator Facilities plasma, focusing, electron, laser 3619
 
  • P. Niknejadi, R.T.P. D’Arcy, J.M. Garland, J. Osterhoff, L. Schaper, B. Schmidt, G.E. Tauscher
    DESY, Hamburg, Germany
  • M. Ferrario, S. Romeo
    INFN/LNF, Frascati, Italy
  • C.A. Lindstrøm
    University of Oslo, Oslo, Norway
  • T.J. Mehrling
    LBNL, Berkeley, USA
  
  FLASHForward, the exploratory FLASH beamline for Future-ORiented Wakefield Accelerator Research and Development, is a European pilot test bed facility for accelerating electron beams to GeV-levels in a few centimeters of ionized gas. The main focus is on the advancement of plasma-based particle acceleration technology through investigation of injection schemes, novel concepts and diagnostics, as well as benchmarking theoretical studies and simulations. Since the plasma wakefield will be driven by the optimal high-current-density electron beams extracted from the FLASH L-band Superconducting RF accelerator, FLASHForward has been in a unique position for studying and providing insight for the design study of next-generation light source and high energy physics facilities such as EuPRAXIA*. Summary of these findings and their broader impact is discussed here.
*P. A. Walker, et. al., "Horizon 2020 EuPRAXIA design study," Journal of Physics Conference Series 874(1):012029, July 2017. 		 
DOI • reference for this paper ※ https://doi.org/10.18429/JACoW-IPAC2019-THPGW019  
About • paper received ※ 15 May 2019       paper accepted ※ 24 May 2019       issue date ※ 21 June 2019  
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THPGW050 Electromagnetic Field of a Charge Moving Through a Channel in Magnetized Plasma plasma, proton, vacuum, electromagnetic-fields 3700
 
  • A.A. Grigoreva, T.Yu. Alekhina, S.N. Galyamin, A.V. Tyukhtin, V.V. Vorobev
    Saint Petersburg State University, Saint Petersburg, Russia
  
  Funding: Work supported by Russian Science Foundation (Grant No. 18-72-10137).
Recent success in beam-driven plasma wakefiled acceleration scheme with two proton bunches propagating through a hollow plasma channel* stimulates the research activity in this area. In this report, we investigate possibilities for additional tuning the structure of the accelerating field by the external magnetic field applied. The structure of surface waves at the channel boundary is of interest, and special attention is paid to the field characteristics that are essential for the wakefield acceleration method (amplitude of the accelerating field, the structure of the deflecting field) and the possibilities of controlling these characteristics by means of the external field.
* Gessner S.J. et al. Proc. IPAC2016. THPPA01. 		 
DOI • reference for this paper ※ https://doi.org/10.18429/JACoW-IPAC2019-THPGW050  
About • paper received ※ 15 May 2019       paper accepted ※ 23 May 2019       issue date ※ 21 June 2019  
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THPGW072 Seeded Self-Modulation of Transversely Asymmetric Long Proton Beams in Plasma plasma, proton, focusing, simulation 3757
 
  • T.A. Perera, C.P. Welsch
    The University of Liverpool, Liverpool, United Kingdom
  • P. Muggli
    MPI-P, München, Germany
  • T.A. Perera, C.P. Welsch
    Cockcroft Institute, Warrington, Cheshire, United Kingdom
  
  Funding: This work is supported by Science and Technology Facilities Council grant ST/P006752/1.
The AWAKE experiment at CERN recently demonstrated the world’s first acceleration of electrons in a proton-driven plasma wakefield accelerator*. Such accelerators show great promise for a new generation of linear e-p colliders using ~1-10 GV/m accelerating fields. Effectively driving a wakefield requires 100-fold self-modulation of the 12 cm Super Proton Synchrotron (SPS) proton beam using a plasma-driven process which must be care-fully controlled to saturation. Previous works have modelled this process assuming azimuthal symmetry of the transverse spatial and momentum profiles **, ***. In this work, 3D particle-in-cell simulations are used to model the self-modulation of such non-round beams. Implications of such effects for efficiently sustaining resonant wakefields are examined.
* Adli, E., et. al. (2018). Nature, 561(7723), 363-367.
** Lotov, K. V. (2015). Physics of Plasmas, 22(10), 103110.
*** Schroeder, C. B., et. al. (2011). Phys. Rev. Lett., 107(14). 		 
DOI • reference for this paper ※ https://doi.org/10.18429/JACoW-IPAC2019-THPGW072  
About • paper received ※ 15 May 2019       paper accepted ※ 23 May 2019       issue date ※ 21 June 2019  
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THPGW073 Status on a Laser Injection in Beam Driven Dielectric Wakefield Accelerator Experiment experiment, plasma, laser, electron 3761
 
  • G. Andonian, T.J. Campese, F.H. O’Shea
    RadiaBeam, Santa Monica, California, USA
  • D.L. Bruhwiler, N.M. Cook
    RadiaSoft LLC, Boulder, Colorado, USA
  • M.E. Conde, D.S. Doran, G. Ha, J.G. Power, J.H. Shao, E.E. Wisniewski
    ANL, Argonne, Illinois, USA
  • J.B. Rosenzweig
    UCLA, Los Angeles, California, USA
  • T. Xu
    Northern Illinois University, DeKalb, Illinois, USA
  
  The generation of high-brightness beams with ultra-low emittance using the plasma photocathode technique has gained significant traction in recent years. The practical execution of a combined plasma wakefield acceleration section and a laser injected typically requires a dual gas medium for precision ionization of low and high ionization thresholds. The concept can be partially simplified in experiment by replacing the plasma wakefield acceleration component with a dielectric wakefield acceleration scheme, sacrificing field gradient but maintaining low emittance beam generation. In this paper, we describe the progress on the design of a hybrid scheme, using laser injection in a gas medium within a dielectric wakefield accelerator structure. The proof-of-concept experiment is planned to take place at the Argonne Wakefield Accelerator.  
DOI • reference for this paper ※ https://doi.org/10.18429/JACoW-IPAC2019-THPGW073  
About • paper received ※ 15 May 2019       paper accepted ※ 22 May 2019       issue date ※ 21 June 2019  
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THPGW088 Transformer Ratio Measurements from Ramped Beams in the Plasma Blowout Regime using Emittance Exchange plasma, emittance, experiment, acceleration 3778
 
  • R.J. Roussel, G. Andonian, W.J. Lynn, J.B. Rosenzweig
    UCLA, Los Angeles, USA
  • M.E. Conde, D.S. Doran, G. Ha, J.G. Power, C. Whiteford, E.E. Wisniewski
    ANL, Argonne, Illinois, USA
  • J. Seok
    UNIST, Ulsan, Republic of Korea
  
  Funding: Work is supported by DOE contract DE-SC0017648.
We present initial measurements from a UCLA-Argonne Wakefield Accelerator collaborative plasma wakefield acceleration (PWFA) experiment aimed at demonstrating the dependence of transformer ratio on longitudinal beam shape. The transformer ratio or the ratio between the maximum acceleration of the witness and the maximum deceleration of the drive beam, is key to a mature, beam-based, plasma wakefield accelerator design. Utilizing the unique capabilities of the emittance exchange (EEX) beamline, we may obtain transformer ratios in excess of six in PWFA. We present the experimental beamline design, relevant beam diagnostics and explore preservation of the longitudinal beam profile. 		 
DOI • reference for this paper ※ https://doi.org/10.18429/JACoW-IPAC2019-THPGW088  
About • paper received ※ 15 May 2019       paper accepted ※ 23 May 2019       issue date ※ 21 June 2019  
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THPTS065 Analysis on the Thermal Response to Beam Impedance Heating of the Post Ls2 Proton Synchrotron Beam Dump impedance, simulation, proton, site 4260
 
  • L. Teofili, F. Giordano, I. Lamas, F.-X. Nuiry, G. Romagnoli, B. Salvant
    CERN, Geneva, Switzerland
  • M. Marongiu, M. Migliorati
    Sapienza University of Rome, Rome, Italy
  
  The High Luminosity Large Hadron Collider (HL-LHC) and the LIU (LHC-Injection Upgrade) projects at CERN are upgrading the whole CERN accelerators chain, increasing beam brightness and intensity. In this scenario, some critical machine components have to be redesigned and rebuilt. Due to the increase in beam intensity, minimizing the electromagnetic interaction between the beam and the device is a crucial design task. Indeed, these interactions could lead to beam instabilities and excessive thermo-mechanical loadings in the device. In this context, this paper presents an example of multi-physics study to investigate the impedance related thermal effects. The analysis is performed on the conceptual design of the new proton synchrotron (PS) internal dump.  
DOI • reference for this paper ※ https://doi.org/10.18429/JACoW-IPAC2019-THPTS065  
About • paper received ※ 26 April 2019       paper accepted ※ 22 May 2019       issue date ※ 21 June 2019  
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