Keyword: wakefield
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MOPAB055 Towards Near-Field Electro-Optical Bunch Profile Monitoring in a Multi-Bunch Environment electron, laser, storage-ring, radiation 227
 
  • P. Schönfeldt, E. Blomley, E. Bründermann, M. Caselle, S. Funkner, N. Hiller, B. Kehrer, A.-S. Müller, M.J. Nasse, G. Niehues, L. Rota, M. Schedler, M. Schuh, M. Weber
    KIT, Karlsruhe, Germany
  
  Funding: This work is funded by the BMBF contract numbers: 05K13VKA and 05K16VKA.
For electron accelerators, electro-optical methods in the near-field have been shown to be a powerful tool to detect longitudinal bunch profiles. In 2013, we demonstrated for the first time, electro-optical bunch profile measurements in a storage ring at the accelerator test facility and synchrotron light source ANKA at the Karlsruhe Institute of Technology (KIT). To study possible bunch-bunch interactions and its effects on the longitudinal dynamics, these measurements need to be performed in a multi-bunch environment. Up to now, due to long-ranging wake-fields the electro-optical monitoring was limited to single-bunch operation. Here, we present our new in-vacuum setup to overcome this limitation. First measurements show reduced wake-fields in particular around 2 ns, where the subsequent bunch can occur in a multi-bunch environment at ANKA. 		 
DOI • reference for this paper ※ https://doi.org/10.18429/JACoW-IPAC2017-MOPAB055  
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MOPAB108 Beam-Based Alignment Studies at CTF3 Using the Octupole Component of CLIC Accelerating Structures octupole, experiment, alignment, collider 371
 
  • J. Ögren, A.K. Bhattacharyya, M. Holz, R.J.M.Y. Ruber, V.G. Ziemann
    Uppsala University, Uppsala, Sweden
  • W. Farabolini
    CEA/DSM/IRFU, France
  
  The Compact Linear Collider (CLIC) uses normal-conducting accelerating structures that are sensitive to wakefield effects and therefore their alignment is extremely important. Due to the four-fold symmetry of the structures, they allow for an octupole component of the rf fields. By scanning the beam transversely we can determine the center of the structures from the shifts in beam position due to the kicks from the octupole field. We present some initial results from measurements at the CLIC test facility 3 at CERN.  
DOI • reference for this paper ※ https://doi.org/10.18429/JACoW-IPAC2017-MOPAB108  
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MOPIK017 Simultaneous Generation of Drive and Witness Beam for Collinear Wakefield Acceleration acceleration, emittance, controls, quadrupole 535
 
  • 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.
Generating the drive and witness bunch for collinear wakefield acceleration (CWFA) requires precise control of the longitudinal bunch shape for each bunch as well as the controlling their separation. The emittance exchange (EEX) beamline and a transverse mask can be used to achieve all of these requirements. First, this EEX-based method can independently control the longitudinal bunch shape of each bunches so that the drive bunch is shaped to generate a high transformer ratio while witness bunch is shaped to suppress its energy spread. Second, the timing jitter between the drive and witness bunch poses a serious limitation to the CWFA scheme but the EEX-based method eliminates this since both bunches are generated at the same time and share the exactly same beamline so there are no relative errors. In this paper, we confirm the feasibility of this EEX-based method for simultaneous generation with simulation for CWFA in a dielectric structure. 		 
DOI • reference for this paper ※ https://doi.org/10.18429/JACoW-IPAC2017-MOPIK017  
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MOPVA027 Measurement of High Power Terahertz with Dielectric Loaded Waveguide at Tsinghua University radiation, electron, experiment, extraction 914
 
  • D. Wang, Y.-C. Du, W. Gai, W.-H. Huang, X.L. Su, C.-X. Tang, Q.L. Tian, L.X. Yan
    TUB, Beijing, People's Republic of China
  • S.P. Antipov
    Euclid Beamlabs LLC, Bolingbrook, USA
  • Y.F. Liang
    Tsinghua University, Beijing, People's Republic of China
  
  Funding: Work supported by the National Nature Science Foundation of China (NSFC Grants No.11475097) and the National Key Scientific Instrument and Equipment Development Project of China (Grants No. 2013YQ12034504)
We have measured an intense THz radiation produced by a sub-picosecond, relativistic electron bunch passing through a dielectric loaded waveguide (DLW) at Tsinghua University accelerator beamline. The DLW was 3 cm long quartz tube with 900 'm inner diameter and 100 'm wall thickness metallized on the outside. Radiated energy of the THz pulse was measured to be proportional to the square of the effective charge. The end of the DLW was cut at an angle for efficient THz pulse extraction. Tens of 'J THz energy per pulse were measured outside the vacuum chamber with a calibrated Golay cell in the experiment.
*wangdan16@mail.tsinghua.edu.cn
*yanlx@mail.tsinghua.edu.cn
 		 
DOI • reference for this paper ※ https://doi.org/10.18429/JACoW-IPAC2017-MOPVA027  
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TUYB1 First Measurements of Trojan Horse Injection in a Plasma Wakefield Accelerator plasma, laser, electron, injection 1252
 
  • B. Hidding, A. Beaton, A.F. Habib, T. Heinemann, G.G. Manahan, P. Scherkl, A. Sutherland, D. Ullmann
    USTRAT/SUPA, Glasgow, United Kingdom
  • E. Adli, C.A. Lindstrøm
    University of Oslo, Oslo, Norway
  • E. Adli, S.J. Gessner
    CERN, Geneva, Switzerland
  • G. Andonian, A. Deng, J.B. Rosenzweig
    UCLA, Los Angeles, California, USA
  • G. Andonian
    RadiaBeam, Santa Monica, California, USA
  • A. Beaton, A.F. Habib, T. Heinemann, B. Hidding, G.G. Manahan, P. Scherkl, A. Sutherland, D. Ullmann
    Cockcroft Institute, Warrington, Cheshire, United Kingdom
  • D.L. Bruhwiler
    RadiaSoft LLC, Boulder, Colorado, USA
  • J.R. Cary
    Tech-X, Boulder, Colorado, USA
  • C.I. Clarke, S.Z. Green, M.J. Hogan, B.D. O'Shea, V. Yakimenko
    SLAC, Menlo Park, California, USA
  • M. Downer, R. Zgadzaj
    The University of Texas at Austin, Austin, Texas, USA
  • T. Heinemann, A. Knetsch
    DESY, Hamburg, Germany
  • T. Heinemann, G. Wittig
    University of Hamburg, Hamburg, Germany
  • O.S. Karger
    University of Hamburg, Institut für Experimentalphysik, Hamburg, Germany
  • M.D. Litos
    Colorado University at Boulder, Boulder, Colorado, USA
  • J.D.A. Smith
    TXUK, Warrington, United Kingdom
  
  Funding: Work supported in part by the U.S. Department of Energy under contract number DE-AC02-76SF00515.
Plasma accelerators support accelerating fields of 100's of GV/m over meter-scale distances and routinely produce femtosecond-scale, multi-kA electron bunches. The so called Trojan Horse underdense photocathode plasma wakefield acceleration scheme combines state-of-the-art accelerator technology with laser and plasma methods and paves the way to improve beam quality as regards emittance and energy spread by many orders of magnitude. Electron beam brightness levels exceeding 1020 Am-2 rad-2 may be reached, and the tunability allows for multi-GeV energies, designer bunches and energy spreads <0.05% in a single plasma accelerator stage. The talk will present results of the international E210 multi-year experimental program at SLAC FACET, which culminated in successful first demonstration of the Trojan Horse method during FACET's final experimental run in 2016. Enabling implications for applications, including high performance plasma-based 5th generation light sources such as hard x-ray FEL's, for which start-to-end simulations are presented, and for high energy physics are discussed. 		 
slides icon Slides TUYB1 [19.089 MB]  
DOI • reference for this paper ※ https://doi.org/10.18429/JACoW-IPAC2017-TUYB1  
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TUPIK001 Upgrade of the Two-Screen Measurement Setup in the AWAKE Experiment proton, plasma, electron, experiment 1682
 
  • M. Turner
    TUG/ITP, Graz, Austria
  • V. Clerc, I. Gorgisyan, E. Gschwendtner, S. Mazzoni, A.V. Petrenko
    CERN, Geneva, Switzerland
  
  The AWAKE project at CERN uses a self-modulated §I{400}{GeV/c} proton bunch to drive GV/m wakefields in a §I10{m} long plasma with an electron density of npe = 7 × 1014 \rm{electrons/cm}3. We present the upgrade of a proton beam diagnostic to indirectly prove that the bunch self-modulated by imaging defocused protons with two screens downstream the end of the plasma. The two-screen diagnostic has been installed, commissioned and tested in autumn 2016 and limitations were identified. We plan to install an upgraded diagnostics to overcome these limitations.  
DOI • reference for this paper ※ https://doi.org/10.18429/JACoW-IPAC2017-TUPIK001  
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TUPIK010 Investigating the Key Parameters of a Staged Laser- and Particle Driven Plasma Wakefield Accelerator Experiment plasma, laser, electron, acceleration 1703
 
  • T. Heinemann, R.W. Aßmann, O. S. Kononenko, A. Martinez de la Ossa
    DESY, Hamburg, Germany
  • J.P. Couperus, A. Irman, A. Köhler, O. Zarini
    Helmholtz-Zentrum Dresden-Rossendorf (HZDR), Institute of Radiation Physics, Dresden, Germany
  • T. Heinemann, B. Hidding
    USTRAT/SUPA, Glasgow, United Kingdom
  • T. Heinemann
    University of Hamburg, Institut für Experimentalphysik, Hamburg, Germany
  • A. Knetsch
    University of Hamburg, Hamburg, Germany
  • T. Kurz
    HZDR, Dresden, Germany
  • U. Schramm
    TU Dresden, Dresden, Germany
  
  Plasma wakefield accelerators can be driven by either a powerful laser pulse (LWFA) or a high-current charged particle beam (PWFA). A plasma accelerator combining both schemes consists of a LWFA providing an electron beam which subsequently drives a PWFA in the highly nonlinear regime. This scenario explicitly makes use of the advantages unique to each method, particularly exploiting the capabilities of PWFA schemes to provide high-brightness beams, while the LWFA stage inherently fulfils the demand for compact high-current electron bunches required as PWFA drivers. Effectively, the sub-sequent PWFA stage operates as beam brightness and energy booster of the initial LWFA output, aiming to match the demanding beam quality requirements of accelerator based light sources. We report on numerical studies towards the implementation of a proof-of-principle experiment at the DRACO laser facility at Helmholtz-Zentrum Dresden-Rossendorf (HZDR).  
DOI • reference for this paper ※ https://doi.org/10.18429/JACoW-IPAC2017-TUPIK010  
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TUPIK018 Experimental Investigation of High Transformer Ratio Plasma Wakefield Acceleration at PITZ plasma, acceleration, experiment, simulation 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 		 
DOI • reference for this paper ※ https://doi.org/10.18429/JACoW-IPAC2017-TUPIK018  
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TUPIK024 Study of High Transformer Ratio Plasma Wakefield Acceleration for Accelerator Parameters of SXFEL Using 3D PIC Simulations plasma, simulation, injection, acceleration 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
 		 
DOI • reference for this paper ※ https://doi.org/10.18429/JACoW-IPAC2017-TUPIK024  
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TUPIK026 Simulations of Positron Capture and Acceleration in the Linear Wakefield of Plasma positron, plasma, laser, emittance 1737
 
  • M.M. Peng, W. Gai
    TUB, Beijing, People's Republic of China
  
  We present the study of positrons capturing dynamics in the wakefield of plasma generated either by a laser or electron beam. Only simplified linear wakefield models were used as first order approximation. By analysing the phase space and beam dynamics, we show that phase space for capturing is rather small, only high brightness beam with very short pulse length can be captured with reasonable rate for wakefields of 1 - 10 GeV/m and wave-length of 100 micron.  
DOI • reference for this paper ※ https://doi.org/10.18429/JACoW-IPAC2017-TUPIK026  
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TUPIK031 Driver-Witness-Bunches for Plasma-Wakefield Acceleration at the MAX IV Linear Accelerator plasma, electron, linac, simulation 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.  
DOI • reference for this paper ※ https://doi.org/10.18429/JACoW-IPAC2017-TUPIK031  
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TUPIK075 ATF2 Beam Halo Collimation System Background and Wakefield Measurements in the 2016 Runs collimation, background, simulation, 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.  
DOI • reference for this paper ※ https://doi.org/10.18429/JACoW-IPAC2017-TUPIK075  
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TUPIK076 Pre-Alignment Techniques Developments and Measurement Results of the Electromagnetic Center of Warm High-Gradient Accelerating Structures simulation, alignment, linac, 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. 		 
DOI • reference for this paper ※ https://doi.org/10.18429/JACoW-IPAC2017-TUPIK076  
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WEPAB031 OCELOT as a Framework for Beam Dynamics Simulations of X-Ray Sources simulation, 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.  
DOI • reference for this paper ※ https://doi.org/10.18429/JACoW-IPAC2017-WEPAB031  
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WEPAB037 Two-Bunch Operation at the FERMI FEL Facility linac, laser, FEL, electron 2663
 
  • G. Penco, E. Allaria, S. Bassanese, P. Cinquegrana, S. Cleva, M.B. Danailov, A.A. Demidovich, S. Di Mitri, M. Ferianis, G. Gaio, D. Gauthier, L. Giannessi, M. Predonzani, F. Rossi, E. Roussel, S. Spampinati, M. Trovò
    Elettra-Sincrotrone Trieste S.C.p.A., Basovizza, Italy
  • L. Giannessi
    ENEA C.R. Frascati, Frascati (Roma), Italy
  • E. Roussel
    PhLAM/CERLA, Villeneuve d'Ascq, France
  
  FERMI is a linac-driven free electron laser (FEL) based upon the High Gain Harmonic Generation (HGHG) scheme. In standard conditions a bunch of 700 pC of charge with sub mm-mrad emittances is accelerated to 1.2-1.5GeV in a normal conducting S-band linac and drives FEL-1 or FEL-2 undula-tor line, which lase respectively in the range 100-20nm or 20-4nm. A number of two-color schemes have been implemented at FERMI for pump/probe experiments, all consisting in making two portions of the same electron bunch lase at two different wavelengths, with a time-separation from 0 to few hundreds of fs. In order to increase the time separation to ns and tens of ns we have explored the acceleration of two inde-pendent electron bunches separated by multiple of the linac main radio-frequency period, i.e. 333ps. Measure-ments and characterization of this two-bunch mode oper-ation are presented, including trajectory control, impact of longitudinal and transverse wakefields on the trailing bunch and manipulation of the longitudinal phase space.  
DOI • reference for this paper ※ https://doi.org/10.18429/JACoW-IPAC2017-WEPAB037  
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WEPAB122 Experimental Demonstration of Ballistic Bunching with Dielectric-Lined Waveguides at Pitz electron, experiment, linac, bunching 2857
 
  • F. Lemery
    University of Hamburg, Hamburg, Germany
  • G.A. Amatuni, B. Grigoryan
    CANDLE, Yerevan, Armenia
  • P. Boonpornprasert, Y. Chen, J.D. Good, M. Krasilnikov, O. Lishilin, G. Loisch, S. Philipp, H.J. Qian, Y. Renier, F. Stephan
    DESY Zeuthen, Zeuthen, Germany
  • P. Piot
    Fermilab, Batavia, Illinois, USA
  • P. Piot
    Northern Illinois University, DeKalb, Illinois, USA
  
  We report on the experimental demonstration of ballistic bunching of photoinjected, nC-scale electron bunches at the PITZ facility. In the experiment, electron bunches emanating from the photocathode were directly focused into a mm-scale dielectric-lined waveguide. The wakefield excited by the bunch acts back onto itself, leading to an energy modulation, which at a relatively low energy of 6~MeV, is converted into a density modulation before entering the linac  ∼ 1~m downstream. We discuss the basic theory, experimental layout and results.  
DOI • reference for this paper ※ https://doi.org/10.18429/JACoW-IPAC2017-WEPAB122  
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WEPAB123 A Phase Matching, Adiabatic Accelerator electron, acceleration, laser, plasma 2861
 
  • F. Lemery
    University of Hamburg, Hamburg, Germany
  • K. Flöttmann
    DESY, Hamburg, Germany
  • F.X. Kärtner
    MIT, Cambridge, Massachusetts, USA
  • F.X. Kärtner
    CFEL, Hamburg, Germany
  • P. Piot
    Fermilab, Batavia, Illinois, USA
  • P. Piot
    Northern Illinois University, DeKalb, Illinois, USA
  
  Tabletop accelerators are a thing of the future. Reducing their size will require scaling down electromagnetic wavelengths; however, without correspondingly high field gradients, particles will be more susceptible to phase-slippage – especially at low energy. We investigate how an adiabatically-tapered dielectric-lined waveguide could maintain phase-matching between the accelerating mode and electron bunch. We benchmark our simple model with CST and implement it into ASTRA; finally we provide a first glimpse into the beam dynamics in a phase-matching accelerator.  
DOI • reference for this paper ※ https://doi.org/10.18429/JACoW-IPAC2017-WEPAB123  
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WEPAB132 Research Program and Recent Results at the Argonne Wakefield Accelerator Facility (AWA) experiment, electron, emittance, acceleration 2885
 
  • M.E. Conde, S.P. Antipov, D.S. Doran, W. Gai, Q. Gao, G. Ha, C.-J. Jing, W. Liu, N.R. Neveu, J.G. Power, J.Q. Qiu, J.H. Shao, Y.R. Wang, C. Whiteford, E.E. Wisniewski, L.M. Zheng
    ANL, Argonne, Illinois, USA
  • S.P. Antipov, C.-J. Jing, J.Q. Qiu
    Euclid TechLabs, LLC, Solon, Ohio, USA
  • Q. Gao, L.M. Zheng
    TUB, Beijing, People's Republic of China
  • G. Ha
    POSTECH, Pohang, Kyungbuk, Republic of Korea
  • N.R. Neveu
    IIT, Chicago, Illinois, USA
  • Y.R. Wang
    IMP/CAS, Lanzhou, People's Republic of China
  
  Funding: Work supported by the U.S. Department of Energy under contract No. DE-AC02-06CH11357
We give an overview of the research program at the Argonne Wakefield Accelerator Facility (AWA), including some highlights of recent experiments. The AWA facility is dedicated to the study of beam physics and the development of technology for future particle accelerators. Two independent electron linacs are used to study wakefield acceleration: 70 MeV high charge electron bunches of up to 100 nC are used to drive wakefields, which can be probed by bunches originating from the same linac or from the 15 MeV linac. Recent Two-Beam-Acceleration (TBA) experiments operating at 11.7 GHz reached accelerating gradients of up to 150 MV/m. No indication of witness beam quality degradation was observed, and bunch charge was preserved during the acceleration process. Two identical TBA setups were used in series in order to demonstrate staging capabilities. Dielectric loaded structures operating at 26 GHz are also used in TBA experiments. Another main thrust of the research program consists of exploring and developing techniques to manipulate the phase space of electron bunches. These efforts include bunch shaping and the exchange of emittances in the transverse and the longitudinal phase spaces 		 
DOI • reference for this paper ※ https://doi.org/10.18429/JACoW-IPAC2017-WEPAB132  
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WEPIK066 Calculation of Wakefields and Higher Order Modes for the Vacuum Chamber of the CMS, ATLAS, ALICE and LHCb Experiments for the HL-LHC vacuum, higher-order-mode, dipole, impedance 3081
 
  • R. Wanzenberg, O. Zagorodnova
    DESY, Hamburg, Germany
  • E. Métral, B. Salvant
    CERN, Geneva, Switzerland
  
  Funding: Partly funded by the European Commission within the Framework Programme 7 Capacities Specific Programme, Grant Agreement 284404.
The High Luminosity Large Hadron Collider (HL-LHC) project was started with the goal to extend the discovery potential of the Large Hadron Collider (LHC). The HL-LHC study implies also upgraded dimensions of the experimental beam pipes of the CMS, ATLAS, ALICE and LHCb experiments. The trapped monopole and dipole Higher Order Modes (HOMs) and the short range wakefields for the new design of the vacuum chambers were calculated with help of the computer codes MAFIA and ECHO2D. The results of the short range wakefields calculations and the HOMs calculations are presented in this report. The short range wakefields are presented in terms of longitudinal and transverse wake potentials and also in terms of loss and kick parameters. Selected results from the HOMs calculations , including the the frequency, the loss parameter, the R/Q and the Q value are presented. 		 
DOI • reference for this paper ※ https://doi.org/10.18429/JACoW-IPAC2017-WEPIK066  
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WEPIK073 Three Dimensional Wake Field for an Electron Moving in Undulator undulator, electron, radiation, electromagnetic-fields 3098
 
  • K. Ohmi
    KEK, Ibaraki, Japan
  
  Electro-magnetic field for given trajectory of an electron is calculated by Lienard-Wiechert potential. The field near the electron moving in an undulator is presented. The field is regarded as a wake field in the undulator. Motion of a bunch is studied in the wake field.  
DOI • reference for this paper ※ https://doi.org/10.18429/JACoW-IPAC2017-WEPIK073  
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WEPIK095 Evaluation of Longitudinal Beam Impedance in the Beam Gas Ionization Monitor of the CERN-PS Accelerator impedance, coupling, simulation, 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.  
DOI • reference for this paper ※ https://doi.org/10.18429/JACoW-IPAC2017-WEPIK095  
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WEPIK100 The Applicability of NEG Coated Undulator Vessels for the CLARA FEL Test Facility vacuum, FEL, undulator, impedance 3181
 
  • O.B. Malyshev, K.B. Marinov, K.J. Middleman, N. Thompson, R. Valizadeh, P.H. Williams
    STFC/DL/ASTeC, Daresbury, Warrington, Cheshire, United Kingdom
  • O.B. Malyshev, K.J. Middleman, N. Thompson, R. Valizadeh, P.H. Williams
    Cockcroft Institute, Warrington, Cheshire, United Kingdom
  
  CLARA is a FEL test facility at Daresbury Laboratory (DL), UK. The undulator vacuum chamber is 20 m long with inner diameter 6 mm and its vacuum performance can benefit from a NEG coating. The thickness of the coating layer must be carefully optimised. A layer ~ 1 um would help the vacuum but a thinner layer would be partially transparent for the EM field reducing the resistive wall wakefields due to the NEG. A very thin layer, however, may not yield the necessary vacuum performance. Two types of NEG coatings produced at DL - dense and columnar - were considered. Their bulk conductivities were measured in a separate study. The resistive wall wakefield impedance was calculated following the standard approach for multilayer vessels. A 250 fs rms electron bunch was generated in ASTRA and its wakefield was obtained from the vessel impedance. The FEL performance was then studied through GENESIS simulations and the result compared to the case with no wakefields. It was found that NEG layers thicker than 100 nm give an unacceptable reduction of the FEL power and the vacuum performance of such thin coatings is unknown. Possible solutions to this problem are discussed.  
DOI • reference for this paper ※ https://doi.org/10.18429/JACoW-IPAC2017-WEPIK100  
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WEPIK106 Impedance and Collective Effects for the Advanced Light Source Upgrade at LBNL impedance, simulation, 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. 		 
DOI • reference for this paper ※ https://doi.org/10.18429/JACoW-IPAC2017-WEPIK106  
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WEPIK109 Experimental Study of Vertical-Longitudinal Coupling Induced by Wakefields at CesrTA lattice, coupling, simulation, 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. 		 
DOI • reference for this paper ※ https://doi.org/10.18429/JACoW-IPAC2017-WEPIK109  
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WEPIK110 Resistive Wall Instability and Impedance Studies of Narrow Undulator Chamber in CHESS-U undulator, lattice, simulation, 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. 		 
DOI • reference for this paper ※ https://doi.org/10.18429/JACoW-IPAC2017-WEPIK110  
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WEPIK113 Entrance and Exit CSR Impedance for Non-Ultrarelativistic Beam impedance, dipole, bunching, FEL 3214
 
  • R. Li
    JLab, Newport News, Virginia, USA
  • C.-Y. Tsai
    Virginia Polytechnic Institute and State University, Blacksburg, Virginia, USA
  
  Funding: Work supported by the Department of Energy, Laboratory Directed Research and Development Funding, under Contract No. DE-AC05-06OR23177
For a high-brightness electron beam being transported through beamlines involving bending systems, the coherent synchrotron radiation (CSR) and longitudinal space charge (LSC) interaction could often cause microbunching instability. The semi-analytical Vlasov solver for microbunching gain* depends on the impedances for the relevant collective effects. The existing results for CSR impedances are usually obtained for the ultrarelativistic limit. To extend the microbunching analysis to cases of low energies, such as the case of an ERL merger, or to density modulations at extremely small wavelength, it is necessary to extend the impedance analysis to the non-ultrarelativistic regime. In this study, we present the impedance analysis for the transient CSR interaction in the non-ultrarelativistic regime, for transients including both entrance to and exit from a magnetic dipole. These impedance results will be compared to their ultra-relativistic counterparts**, and the corresponding wakefield obtained from the impedance for low-energy beams will be compared with the existing results of transient CSR wakefield for general beam energies***.
* C.-Y. Tsai et al., Proc. of IPAC'15, 596 (2015).
** C. Mitchell et al ., Proc. of IPAC'13, 1832 (2014).
*** E. L. Saldin et al ., Nucl. Instrum. Meth. A 398, 373 (1997). 		 
DOI • reference for this paper ※ https://doi.org/10.18429/JACoW-IPAC2017-WEPIK113  
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WEPVA018 Drive-Witness Acceleration Scheme Based on Corrugated Dielectric mm-Scale Capillary acceleration, laser, electron, experiment 3292
 
  • K. Lekomtsev, S.T. Boogert, P. Karataev, A. Lyapin
    JAI, Egham, Surrey, United Kingdom
  • A. Aryshev, M. Shevelev, N. Terunuma, J. Urakawa
    KEK, Ibaraki, Japan
  • A.A. Tishchenko
    MEPhI, Moscow, Russia
  
  Funding: This project has received funding from the European Union Horizon 2020 research and innovation programme under the Marie Sklodowska-Curie grant agreement No 655179.
In this paper, we investigate a corrugated mm-scale capillary as a compact accelerating structure in a drive-witness acceleration scheme, and suggest a methodology to measure acceleration of a witness bunch. Two typical measurements and the energy gain in a witness bunch as a function of the distance between bunches are discussed. A corrugated capillary is considered as an accelerator/decelerator with an adjustable wakefield pattern depending on a transverse beam position. 		 
DOI • reference for this paper ※ https://doi.org/10.18429/JACoW-IPAC2017-WEPVA018  
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WEPVA021 Phase Space Manipulation of Sub-Picosecond Electron Bunches Using Dielectric Wakefield Structures emittance, FEL, simulation, 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.  
DOI • reference for this paper ※ https://doi.org/10.18429/JACoW-IPAC2017-WEPVA021  
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WEPVA022 RECENT TWO-BEAM ACCELERATION ACTIVITIES AT ARGONNE WAKEFIELD ACCELERATOR FACILITY acceleration, experiment, accelerating-gradient, impedance 3305
 
  • J.H. Shao, S.P. Antipov, M.E. Conde, W. Gai, Q. Gao, G. Ha, W. Liu, N.R. Neveu, J.G. Power, Y.R. Wang, E.E. Wisniewski, L.M. Zheng
    ANL, Argonne, Illinois, USA
  • C.-J. Jing, J.Q. Qiu
    Euclid TechLabs, LLC, Solon, Ohio, USA
  • J. Shi, D. Wang
    TUB, Beijing, People's Republic of China
  
  The Two-Beam Acceleration (TBA) is a modified approach to the structure-based wakefield acceleration which may meet the luminosity, efficiency, and cost requirement of a future linear collider. Recently, various TBA experiments have been carried out at the Argonne Wakefield Accelerator Facility (AWA). With X-band metallic power extractors and accelerators, a 70 MeV/m average accelerating gradient has been demonstrated in two stages while a 150 MeV/m gradient as well as 300 MW extracted power have been achieved in a single stage. In addition, low cost K-band dielectric power extractor and accelerator have also been developed. The preliminary results show power extraction of 55 MW and an average accelerating gradient of 28 MeV/m.  
DOI • reference for this paper ※ https://doi.org/10.18429/JACoW-IPAC2017-WEPVA022  
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WEPVA067 Preliminary Results on the Resonant Excitation of THz Wakefield in a Multi-Mode Dielectric Loaded Waveguide by Bunch Train electron, radiation, experiment, space-charge 3426
 
  • D. Wang, Y.-C. Du, W. Gai, W.-H. Huang, L. Niu, X.L. Su, C.-X. Tang, Q.L. Tian, L.X. Yan
    TUB, Beijing, People's Republic of China
  • S.P. Antipov
    Euclid TechLabs, LLC, Solon, Ohio, USA
  • Y.F. Liang
    Tsinghua University, Beijing, People's Republic of China
  
  Funding: Work supported by the National Nature Science Foundation of China (NSFC Grants No.11475097) and the National Key Scientific Instrument and Equipment Development Project of China (Grants No. 2013YQ12034504)
We report the preliminary experimental results on the resonant excitation of THz wakefield in a multi-mode dielectric loaded waveguide (DLW) by electron bunch train at the Tsinghua University accelerator beamline. The bunch train with certain longitudinal periodicity was generated based on nonlinear longitudinal space charge oscillation [1]. By passing such bunch train through a multi-mode DLW, we observed selective excitation of the fifth longitudinal mode (TM05 mode) was resonantly excited. Future experiment plan is to tune the bunch train interval with a chicane in the beamline in order to selectively excite arbitrary mode for tunable THz radiation source with multi-mode DLWs.
*wangdan16@mail.tsinghua.edu.cn
*yanlx@mail.tsinghua.edu.cn
 		 
DOI • reference for this paper ※ https://doi.org/10.18429/JACoW-IPAC2017-WEPVA067  
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THOBA2 Coherent Synchrotron Radiation and Wake Fields With Discontinuous Galerkin Time Domain Methods vacuum, synchrotron, synchrotron-radiation, radiation 3649
 
  • D. A. Bizzozero, H. De Gersem, E. Gjonaj
    TEMF, TU Darmstadt, Darmstadt, Germany
  
  Funding: This work is supported by DESY, Hamburg.
Coherent synchrotron radiation (CSR) is an essential issue in modern accelerators. We propose a new method to examine CSR in the time domain using an unstructured Discontinuous Galerkin (DG) method. The method uses a 2D spatial discretization in the longitudinal and transverse coordinates (Z,X) with a Fourier series decomposition in the transverse coordinate Y and computes the fields modally. Additionally, by alignment of mesh element interfaces along a source reference orbit, DG methods can naturally handle discontinuous or thin sources in the transverse X direction. We present an overview of the method, illustrate it by calculating wake potentials in a model problem, and in a bunch compressor. 		 
slides icon Slides THOBA2 [2.526 MB]  
DOI • reference for this paper ※ https://doi.org/10.18429/JACoW-IPAC2017-THOBA2  
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THPAB021 Wake Field and Head-Tail Instability in Beam-Beam Collision with a Large Crossing Angle electron, positron, simulation, 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 σzθ/σx>>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.  
DOI • reference for this paper ※ https://doi.org/10.18429/JACoW-IPAC2017-THPAB021  
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THPAB031 Study of Beam Break Up in Irradiation Linacs linac, electron, experiment, simulation 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.  
DOI • reference for this paper ※ https://doi.org/10.18429/JACoW-IPAC2017-THPAB031  
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THPAB057 Method to Calculate the Longitudinal Impedance From a Partial Wakefield Simulation impedance, simulation, 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.  
DOI • reference for this paper ※ https://doi.org/10.18429/JACoW-IPAC2017-THPAB057  
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THPIK045 Design of a C-band Travelling-wave Accelerating Structure at IHEP cavity, impedance, linac, simulation 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.  
DOI • reference for this paper ※ https://doi.org/10.18429/JACoW-IPAC2017-THPIK045  
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THPVA022 Comparison of Different Methods to Calculate Induced Voltage in Longitudinal Beam Dynamics Codes impedance, simulation, 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.  
DOI • reference for this paper ※ https://doi.org/10.18429/JACoW-IPAC2017-THPVA022  
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