Keyword: wakefield
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MOPLB01 Emittance Control for Different FACET Beam Setups in the SLAC Linac linac, quadrupole, emittance, klystron 138
 
  • F.-J. Decker, W.S. Colocho, N. Lipkowitz, Y. Nosochkov, J. Sheppard, H. Smith, Y. Sun, M.-H. Wang, G.R. White, U. Wienands, M. Woodley, G. Yocky
    SLAC, Menlo Park, California, USA
  
  Funding: Work supported by U.S. Department of Energy, Contract DE-AC02-76SF00515.
The linac beam at SLAC requires different setups for different users at FACET (Facility for Advanced aCcelerator Experimental Tests) area, like highly compressed, intense bunches, or lower charge, long bunches. These require typically a lengthy tuning effort since with a energy-time correlation ("chirp") bunch transverse wakefield kicks can be compensated with dispersive trajectory oscillations and vice versa. Lowering the charge or changing the bunch length will destroy this delicate balance. Besides the typical steering to minimize BPMs (Beam Position Monitors) with correctors, we applied different techniques to try to localize beam disturbances like dispersion with phase changes, RF-kicks and RF quadrupole fields turning a klystron off and on, or varying the phase, and finally wakefield kicks with different beam intensities. It is also important to quantify BPM to quadrupole offsets with "bow-tie" plot and that the correctors give the expected kicks with orbit response matrix measurements. 		 
slides icon Slides MOPLB01 [0.826 MB]  
 
MOPLB03 Advances in Beam Tests of Dielectric Based Accelerating Structures acceleration, electron, laser, linac 144
 
  • A. Kanareykin, S.P. Antipov, J.E. Butler, C.-J. Jing
    Euclid TechLabs, LLC, Solon, Ohio, USA
  • W. Gai
    ANL, Argonne, USA
  • V. Yakimenko
    BNL, Upton, Long Island, New York, USA
  
  Funding: US Department of Energy
Diamond is being evaluated as a dielectric material for dielectric loaded accelerating structures. It has a very low microwave loss tangent, high thermal conductivity, and supports high RF breakdown fields. We report on progress in our recent beam tests of the diamond based accelerating structures of the Ka-band and THz frequency ranges. Wakefield breakdown test of a diamond-loaded accelerating structure has been carried out at the ANL/AWA accelerator. The high charge beam from the AWA linac (~70 nC, σz = 2.5 mm) was passed through a rectangular diamond loaded resonator and induce an intense wakefield. A groove is cut on the diamond to enhance the field. Electric fields up to 0.3 GV/m has been detected on the diamond surface to attempt to initiate breakdown. A surface analysis of the diamond has been performed before and after the beam test. Wakefield effects in a 250 GHz planar diamond accelerating structure has been observed at BNL/ATF accelerator as well. We have directly measured the mm-wave wake fields induced by subpicosecond, intense relativistic electron bunches in a diamond loaded accelerating structure via the dielectric wake-field acceleration mechanism. 		 
slides icon Slides MOPLB03 [1.986 MB]  
 
MOPLB05 Applications of Compact Dielectric-Based Accelerators coupling, multipactoring, impedance, electron 150
 
  • C.-J. Jing, S.P. Antipov, A. Kanareykin, P. Schoessow
    Euclid TechLabs, LLC, Solon, Ohio, USA
  • M.E. Conde, W. Gai, J.G. Power
    ANL, Argonne, USA
  
  Important progress on the development of dielectric based accelerators has been made experimentally and theoretically in the past few years. One advantage of dielectric accelerators over the metallic counterparts is its compact size, which may attract some applications in industrial or medical accelerators. In this article, we discuss the design and technologies of dielectric based accelerators toward these needs.  
 
MOPLB08 Normal Conducting Deflecting Cavity Development at the Cockcroft Institute cavity, beam-loading, damping, electron 159
 
  • G. Burt, P.K. Ambattu, A.C. Dexter, C. Lingwood, B.J. Woolley
    Cockcroft Institute, Lancaster University, Lancaster, United Kingdom
  • S.R. Buckley, P. Goudket, C. Hill, P.A. McIntosh, J.W. McKenzie, A.E. Wheelhouse
    STFC/DL/ASTeC, Daresbury, Warrington, Cheshire, United Kingdom
  • V.A. Dolgashev
    SLAC, Menlo Park, California, USA
  • A. Grudiev
    CERN, Geneva, Switzerland
  • R.M. Jones
    UMAN, Manchester, United Kingdom
  
  Funding: This work has been supported by STFC and the EU through FP7 EUCARD.
Two normal conducting deflecting structures are currently being developed at the Cockcroft Institute, one as a crab cavity for CLIC and one for bunch slice diagnostics on low energy electron beams for EBTF at Daresbury. Each has its own challenges that need overcome. For CLIC the phase and amplitude tolerances are very stringent and hence beamloading effects and wakefields must be minimised. Significant work has been undertook to understand the effect of the couplers on beamloading and the effect of the couplers on the wakefields. For EBTF the difficulty is avoiding the large beam offset caused by the cavities internal deflecting voltage at the low beam energy. Propotypes for both cavities have been manufactured and results will be presented. 		 
slides icon Slides MOPLB08 [1.572 MB]  
 
MOPLB11 The Upgraded Argonne Wakefield Accelerator Facility (AWA): a Test-Bed for the Development of High Gradient Accelerating Structures and Wakefield Measurements electron, gun, linac, acceleration 168
 
  • M.E. Conde, D.S. Doran, W. Gai, R. Konecny, W. Liu, J.G. Power, Z.M. Yusof
    ANL, Argonne, USA
  • S.P. Antipov, C.-J. Jing
    Euclid TechLabs, LLC, Solon, Ohio, USA
  • E.E. Wisniewski
    Illinois Institute of Technology, Chicago, Illinois, USA
  
  Funding: Work supported by the U.S. Department of Energy under contract No. DE-AC02-06CH11357.
Electron beam driven wakefield acceleration is a bona fide path to reach high gradient acceleration of electrons and positrons. With the goal of demonstrating the feasibility of this concept with realistic parameters, well beyond a proof-of-principle scenario, the AWA Facility is currently undergoing a major upgrade that will enable it to achieve accelerating gradients of hundreds of MV/m and energy gains on the order of 100 MeV per structure. A key aspect of the studies and experiments carried out at the AWA facility is the use of relatively short RF pulses (15 – 25 ns), which is believed to mitigate the risk of breakdown and structure damage. The upgraded facility will utilize long trains of high charge electron bunches to drive wakefields in the microwave range of frequencies (8 to 26 GHz), generating RF pulses with GW power levels. 		 
slides icon Slides MOPLB11 [0.900 MB]  
 
MOPB001 Emittance Control for Different FACET Beam Setups in the SLAC Linac linac, quadrupole, emittance, klystron 174
 
  • F.-J. Decker, W.S. Colocho, N. Lipkowitz, Y. Nosochkov, J. Sheppard, H. Smith, Y. Sun, M.-H. Wang, G.R. White, U. Wienands, M. Woodley, G. Yocky
    SLAC, Menlo Park, California, USA
  
  Funding: Work supported by U.S. Department of Energy, Contract DE-AC02-76SF00515.
The linac beam at SLAC requires different setups for different users at FACET (Facility for Advanced aCcelerator Experimental Tests) area, like highly compressed, intense bunches, or lower charge, long bunches. These require typically a lengthy tuning effort since with a energy-time correlation ("chirp") bunch transverse wakefield kicks can be compensated with dispersive trajectory oscillations and vice versa. Lowering the charge or changing the bunch length will destroy this delicate balance. Besides the typical steering to minimize BPMs (Beam Position Monitors) with correctors, we applied different techniques to try to localize beam disturbances like dispersion with phase changes, RF-kicks and RF quadrupole fields turning a klystron off and on, or varying the phase, and finally wakefield kicks with different beam intensities. It is also important to quantify BPM to quadrupole offsets with "bow-tie" plot and that the correctors give the expected kicks with orbit response matrix measurements. 		 
 
MOPB016 In-situ Measurement of Beam-induced Fields in the S-band Accelerating Structures of the Diamond Light Source linac linac, multipole, higher-order-mode, dipole 204
 
  • C. Christou
    Diamond, Oxfordshire, United Kingdom
  
  The Diamond pre-injector linac uses two 5.2 m DESY linac II-type accelerating structures to generate a 100 MeV electron beam suitable for injection into the booster synchrotron. The structures are powered independently by two high-power S-band klystrons and are designed to operate at 3 GHz. Higher order modes up to 14 GHz induced by beam in unpowered accelerating and bunching structures have been directly measured using directional couplers in the high-power waveguide network. These modes are compared with an electromagnetic simulation of the structures. The negative impact of higher-order wakes on the bunch trains used at Diamond is considered, and the use of the multipole field measurement for alignment of the beam to the structure is investigated.  
 
MOPB041 Advances in Beam Tests of Dielectric Based Accelerating Structures acceleration, electron, laser, linac 264
 
  • A. Kanareykin, S.P. Antipov, J.E. Butler, C.-J. Jing
    Euclid TechLabs, LLC, Solon, Ohio, USA
  • W. Gai
    ANL, Argonne, USA
  • V. Yakimenko
    BNL, Upton, Long Island, New York, USA
  
  Funding: US Department of Energy
Diamond is being evaluated as a dielectric material for dielectric loaded accelerating structures. It has a very low microwave loss tangent, high thermal conductivity, and supports high RF breakdown fields. We report on progress in our recent beam tests of the diamond based accelerating structures of the Ka-band and THz frequency ranges. Wakefield breakdown test of a diamond-loaded accelerating structure has been carried out at the ANL/AWA accelerator. The high charge beam from the AWA linac (~70 nC, σz = 2.5 mm) was passed through a rectangular diamond loaded resonator and induce an intense wakefield. A groove is cut on the diamond to enhance the field. Electric fields up to 0.3 GV/m has been detected on the diamond surface to attempt to initiate breakdown. A surface analysis of the diamond has been performed before and after the beam test. Wakefield effects in a 250 GHz planar diamond accelerating structure has been observed at BNL/ATF accelerator as well. We have directly measured the mm-wave wake fields induced by subpicosecond, intense relativistic electron bunches in a diamond loaded accelerating structure via the dielectric wake-field acceleration mechanism. 		 
 
MOPB043 Detailed Analysis of the Long-Range Wakefield in the Baseline Design of the CLIC Main Linac damping, HOM, factory, impedance 270
 
  • V.F. Khan, A. Grudiev
    CERN, Geneva, Switzerland
  
  The baseline design for the accelerating structure of the CLIC main linac relies on strong damping of transverse higher order modes (HOMs). Each accelerating cell is equipped with four damping waveguides that enables HOM energy to propagate to damping loads. Most of the HOMs decay exponentially with a Q-factor of about 10 however, there are modes with higher Q-factors. Though the amplitude of the high Q modes is nearly two orders of magnitude smaller than the dominating lowest dipole mode, their cumulative effect over the entire bunch train may be significant and dilute the beam emittance to unacceptable level. In this paper we report on an accurate calculation of the long-range wakefield and its overall effect on beam dynamics. We also discuss possible measures to minimise its effect in a tapered structure.  
 
MOPB047 Applications of Compact Dielectric Based Accelerators coupling, multipactoring, impedance, electron 279
 
  • C.-J. Jing, S.P. Antipov, A. Kanareykin, P. Schoessow
    Euclid TechLabs, LLC, Solon, Ohio, USA
  • M.E. Conde, W. Gai, J.G. Power
    ANL, Argonne, USA
  
  Important progress on the development of dielectric based accelerators has been made experimentally and theoretically in the past few years. One advantage of dielectric accelerators over the metallic counterparts is its compact size, which may attract some applications in industrial or medical accelerators. In this article, we discuss the design and technologies of dielectric based accelerators toward these needs.  
 
MOPB079 Normal Conducting Deflecting Cavity Development at the Cockcroft Institute cavity, beam-loading, damping, electron 357
 
  • G. Burt, P.K. Ambattu, A.C. Dexter, C. Lingwood, B.J. Woolley
    Cockcroft Institute, Lancaster University, Lancaster, United Kingdom
  • S.R. Buckley, P. Goudket, C. Hill, P.A. McIntosh, J.W. McKenzie, A.E. Wheelhouse
    STFC/DL/ASTeC, Daresbury, Warrington, Cheshire, United Kingdom
  • V.A. Dolgashev
    SLAC, Menlo Park, California, USA
  • A. Grudiev
    CERN, Geneva, Switzerland
  • R.M. Jones
    UMAN, Manchester, United Kingdom
  
  Funding: This work has been supported by STFC and the EU through FP7 EUCARD.
Two normal conducting deflecting structures are currently being developed at the Cockcroft Institute, one as a crab cavity for CLIC and one for bunch slice diagnostics on low energy electron beams for EBTF at Daresbury. Each has its own challenges that need overcome. For CLIC the phase and amplitude tolerances are very stringent and hence beamloading effects and wakefields must be minimised. Significant work has been undertook to understand the effect of the couplers on beamloading and the effect of the couplers on the wakefields. For EBTF the difficulty is avoiding the large beam offset caused by the cavities internal deflecting voltage at the low beam energy. Propotypes for both cavities have been manufactured and results will be presented. 		 
 
MOPB084 Design of a C-band Disk-loaded Type Accelerating Structure for a Higher Pulse Repetition Rate in the SACLA Accelerator. cavity, laser, accelerating-gradient, electron 372
 
  • T. Sakurai, T. Inagaki, Y. Otake
    RIKEN SPring-8 Center, Sayo-cho, Sayo-gun, Hyogo, Japan
  • H. Ego
    JASRI/SPring-8, Hyogo-ken, Japan
  
  The higher pulse repetition rate of the SACLA accelerator provides a higher rate of X-ray laser pulses to expand ability of user experiments, such as simultaneously providing the laser to several beamlines and reducing a measuring time in the experiment. Therefore, we studied on a C-band accelerating structure for a higher pulse rate above 120 pps than that of the present case of 60 pps. The designed structure adopts a TM01-2π/3 mode disk-loaded type with a quasi-constant gradient . Since higher repetition rate operation is inclined to increase a number of vacuum electrical discharges, it is required to reduce the surface electric field in the structure. We designed an ellipsoidal curvature shape around an iris aperture, which reduces the maximum surface field by 20%. Since the higher repetition rate also increases the heat load of the structure, in simulation, we optimized cooling channels to obtain acceptable frequency detuning. As the results of the design, an accelerating gradient of more than 40 MV/m will be expected, when an input RF power of 80 MW is applied to the structure. In this paper, we report the design of the C-band accelerating structure and its rf properties.  
 
MOPB093 The Upgraded Argonne Wakefield Accelerator Facility (AWA): a Test-Bed for the Development of High Gradient Accelerating Structures and Wakefield Measurements electron, gun, linac, acceleration 392
 
  • M.E. Conde, D.S. Doran, W. Gai, R. Konecny, W. Liu, J.G. Power, Z.M. Yusof
    ANL, Argonne, USA
  • S.P. Antipov, C.-J. Jing
    Euclid TechLabs, LLC, Solon, Ohio, USA
  • E.E. Wisniewski
    Illinois Institute of Technology, Chicago, Illinois, USA
  
  Funding: Work supported by the U.S. Department of Energy under contract No. DE-AC02-06CH11357.
Electron beam driven wakefield acceleration is a bona fide path to reach high gradient acceleration of electrons and positrons. With the goal of demonstrating the feasibility of this concept with realistic parameters, well beyond a proof-of-principle scenario, the AWA Facility is currently undergoing a major upgrade that will enable it to achieve accelerating gradients of hundreds of MV/m and energy gains on the order of 100 MeV per structure. A key aspect of the studies and experiments carried out at the AWA facility is the use of relatively short RF pulses (15 – 25 ns), which is believed to mitigate the risk of breakdown and structure damage. The upgraded facility will utilize long trains of high charge electron bunches to drive wakefields in the microwave range of frequencies (8 to 26 GHz), generating RF pulses with GW power levels. 		 
 
TUPB001 The Fine Structure of the Zone of Particle Interaction with a Finite Length Periodic Structure simulation, impedance, diagnostics, emittance 473
 
  • V.V. Paramonov
    RAS/INR, Moscow, Russia
  
  The periodic constant impedance deflecting structures are widely used for a special beam diagnostic in FEL facilities. The method, based on frequency domain approach, was developed to estimate long range wake fields structure parameters in a wide frequency range. It is shown, that regardless to number of cells in the structure, at each passband to the zone of particle effective interaction with the structure belongs several, at least three modes. The usual time domain simulations provide the total estimation for loss factor or kick factor values and modes separation in the time domain approach requires enormous simulations.