WEYBA —  Wednesday Parallel Session 3   (04-Sep-19   10:30—12:30)
Chair: C.B. Schroeder, LBNL, Berkeley, California, USA
Paper Title Page
AWAKE, Proton Bunch Self-Modulation and Electron Acceleration  
  • S.J. Gessner
    CERN, Geneva, Switzerland
  AWAKE has demonstrated the controlled self-modulation of a high energy proton bunch. Basic beam plasma interaction physics was observed and characterized. This led to the driving of large amplitude wakefields suitable for external electron injection and acceleration. Electrons were accelerated to 2GeV. The concept and the experiment will be introduced. Detailed experimental results will be presented. Possible future experiments and applications will be outlined.  
slides icon Slides WEYBA1 [32.276 MB]  
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Petawatt Laser Guiding and Electron Beam Acceleration to 8 GeV in a Laser-Heated Capillary Discharge Waveguide  
  • A.J. Gonsalves
    LBNL, Berkeley, California, USA
  Funding: Office of Science, Office of High Energy Physics, of the U.S. Department of Energy under Contracts No. DE- AC02-05CH11231 and No. DE-FG02-12ER41798. NSF under Grant No. PHY-1632796
Laser plasma accelerators are able to generate large acceleration gradients, tens to hundreds of GV/m, several orders of magnitude larger than conventional radio frequency technology. To achieve high beam energies, preformed plasma waveguides can be used to mitigate laser diffraction of focused laser pulses, increasing the acceleration length and the energy gain for a given laser power. Here we report on guiding of relativistically intense laser pulses with PW peak power over 20 diffraction lengths by increasing the focusing strength of a capillary discharge waveguide using laser inverse Bremsstrahlung heating. This allowed production of electron beams with quasi-monoenergetic peaks in energy up to 7.8 GeV,* almost double what was previously demonstrated.**
* A. J. Gonsalves, et al., Phys. Rev. Lett. Phys. Rev. Lett. 122, 084801 (2018).
** W. P. Leemans, A. J. Gonsalves, et al., Phys. Rev. Lett. 113, 245002 (2014).
slides icon Slides WEYBA2 [23.069 MB]  
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WEYBA3 Tolerances for Plasma Wakefield Acceleration Drivers 614
  • G.R. White, T.O. Raubenheimer
    SLAC, Menlo Park, California, USA
  Transverse jitter tolerances are considered for beam-driven plasma accelerators. A simple model for jitter transfer from the drive to witness beam was developed and con-crete examples were studied for: high-brightness witness bunch injectors; high-energy boosters for FEL’s; and future Linear Colliders. For the LC application, we con-sider a superconducting Linac designed to minimize the jitter conditions of the drive beam. We use a start-to-end tracking model to simulate expected jitter performance. The tolerances on each subsystem of the driver Linac are found to be very tight, especially for magnet vibration which must be controlled at the sub-nm level.
Work supported by the Department of Energy under Contract Number: DE-AC02-76SF00515.
slides icon Slides WEYBA3 [6.178 MB]  
DOI • reference for this paper ※ https://doi.org/10.18429/JACoW-NAPAC2019-WEYBA3  
About • paper received ※ 27 August 2019       paper accepted ※ 02 September 2019       issue date ※ 08 October 2019  
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Beam Induced Ionization Injection of Shaped Electron Bunches  
  • N. Vafaei-Najafabadi, L.D. Amorim
    Stony Brook University, Stony Brook, USA
  Funding: Simulations were conducted on NERSC facility, operated under Contract No. DE-AC02-5CH11231, and of SEAWULF at Stony Brook University.
Particle-driven Plasma Wakefield Accelerators (PWFAs) are promising candidates for future free electron laser and collider applications. In PWFAs, energy is transferred from a relativistic drive beam to a trailing bunch in a plasma wake. One of the challenges of PWFAs is reducing energy spread of the beam from typically few percent to the required 0.1% range. This can be accomplished by generating a trailing bunch with a trapezoidal density profile, which will allow the PWFA to operate in the beam-loading regime, therefore circumventing the energy-spread growth of the trailing beam during acceleration. In this work we show how the Beam Induced Ionization Injection (BIII) technique can produce a trailing bunch of electrons with a trapezoidal shape suitable for beam-loading. In BIII, the trailing beam is created by ionization injection of an impurity due to the increased field of the beam during betatron oscillations. By tailoring the longitudinal profile of the impurity, we can shape the injected trailing electron bunch to reach the beam-loading regime. We will present results of numerical simulations done to model BIII shaped beams with the Particle In Cell code OSIRIS*.
* R. A. Fonseca et al., Lect. Notes Comput. Sci. 2331, 342 (2002).
slides icon Slides WEYBA4 [9.514 MB]  
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WEYBA5 Diamond Field Emitter Array Cathode Experimental Tests in RF Gun 618
  • 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, Lemont, Illinois, USA
  Funding: LANL/LDRD
Diamond Field Emitter Array (DFEA) cathodes are arbitrarily shaped arrays of sharp (~50 nm tip size) nano-diamond pyramids with bases on the order of 3 to 25 microns and pitches 5 microns and greater. These cathodes have demonstrated very high bunch charge in tests at the L-band RF gun at the Argonne National Laboratory (ANL) Advanced Cathode Test Stand (ACTS). Intrinsically shaped electron beams have a variety of applications, but primarily to achieve high transformer ratios for Dielectric Wakefield Accelerators (DWA) when used in conjunction with Emittance Exchange (EEX) systems. Here we will present results from a number of recent cathode tests including bunch charge and YAG images. We have demonstrated shaped beam transport down the 2.54-meter beamline. In addition we will present emission simulations that demonstrate shielding effects for this geometry.
slides icon Slides WEYBA5 [13.017 MB]  
DOI • reference for this paper ※ https://doi.org/10.18429/JACoW-NAPAC2019-WEYBA5  
About • paper received ※ 01 September 2019       paper accepted ※ 19 November 2019       issue date ※ 08 October 2019  
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WEYBA6 A High-Precision Emission Computational Model for Ultracold Electron Sources 622
SUPLE14   use link to see paper's listing under its alternate paper code  
  • A.J. Tencate, B. Erdelyi
    Northern Illinois University, DeKalb, Illinois, USA
  Funding: This work is supported by NSF award #1535401.
The high-intensity, high-brightness and precision frontiers for charged particle beams are an increasingly important focus for study. Ultimately for electron beam applications, including FELs and microscopy, the quality of the source is the limiting factor in the final quality of the beam. It is imperative to understand and develop a new generation of sub-Kelvin electron sources, and the current state of PIC codes are not precise enough to adequately treat this ultracold regime. Our novel computational framework is capable of modelling electron field emission from nanoscale structures on a substrate, with the precision to handle the ultracold regime. This is accomplished by integrating a newly developed Poisson integral solver capable of treating highly curved surfaces and an innovative collisional N-body integrator to propagate the emitted electron with prescribed accuracy. The electrons are generated from a distribution that accounts for quantum confinement and material properties and propagated to the cathode surface. We will discuss the novel techniques that we have developed and implemented, and show emission characteristics for several cathode designs.
slides icon Slides WEYBA6 [4.215 MB]  
poster icon Poster WEYBA6 [5.758 MB]  
DOI • reference for this paper ※ https://doi.org/10.18429/JACoW-NAPAC2019-WEYBA6  
About • paper received ※ 27 August 2019       paper accepted ※ 05 September 2019       issue date ※ 08 October 2019  
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