Author: Carlsten, B.E.
Paper Title Page
TUXGBF2 Higher-Order-Mode Effects in Tesla-Type Superconducting RF Cavities on Electron Beam Quality 612
 
  • A.H. Lumpkin, N. Eddy, D.R. Edstrom, P.S. Prieto, J. Ruan, R.M. Thurman-Keup
    Fermilab, Batavia, Illinois, USA
  • K. Bishofberger, B.E. Carlsten
    LANL, Los Alamos, New Mexico, USA
  • O. Napoly
    CEA/DSM/IRFU, France
 
  Funding: *Work at Fermilab supported by FRA, LLC under Contract No. DE-AC02-07CH11359 with the U.S. Dept. of Energy. **Work at LANL supported by U.S. Dept. of Energy through the LANL/LDRD Program.
We report the direct observations of the correlation of higher order modes (HOMs) generated by off-axis electron beam steering in TESLA-type SCRF cavities and sub-macropulse beam centroid shifts (with the concomitant effect on averaged beam size and emittance). The experiments were performed at the Fermilab Accelerator Science and Technology (FAST) facility using its unique configuration of a PC rf gun injecting beam into two separated 9-cell cavities in series with corrector magnets and beam position monitors (BPMs) located before, between, and after them. The ~100-kHz oscillations with up to 300-µm amplitudes at downstream locations were observed in a 3-MHz micropulse repetition rate beam with charges of 500 and 1000 pC/b, although the effects were much reduced at 100 pC/b. The studies were based on HOM detector circuitry targeting the first and second dipole passbands, rf BPM bunch-by-bunch data, and imaging cameras viewing multi-slit images for emittance assessments at 33 MeV. Initial calculations reproduced a key feature of the phenomena. In principle, these results may be scaled to cryomodule configurations of major accelerator facilities.
 
slides icon Slides TUXGBF2 [3.636 MB]  
DOI • reference for this paper ※ https://doi.org/10.18429/JACoW-IPAC2018-TUXGBF2  
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THPAK044 Self-Consistent Modeling using a Lienard-Wiechert Particle-Mesh Method 3313
 
  • R.D. Ryne, C.E. Mitchell, J. Qiang
    LBNL, Berkeley, California, USA
  • B.E. Carlsten
    LANL, Los Alamos, New Mexico, USA
 
  In this paper we describe a parallel, large-scale simulation capability using a Lienard-Wiechert Particle-Mesh (LWPM) method. The approach is a natural extension of the convolution-based technique to solve the Poisson equation in space-charge codes. It provides a unified method to compute both Coulomb-like self-fields and radiative phenomena like coherent synchrotron radiation (CSR). The approach brings together several mathematical and computational capabilities including the use of integrated Green function (IGF) methods and adaptive quadrature methods. We will describe the theoretical model and our progress to date.  
DOI • reference for this paper ※ https://doi.org/10.18429/JACoW-IPAC2018-THPAK044  
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FRYGB2
Applications of Compact Accelerators in Space for National Security  
 
  • B.E. Carlsten
    LANL, Los Alamos, New Mexico, USA
 
  Relativistic electrons can oscillate above the Earth trapped in the radiation belts (known as the Van Allen Belts). These electrons, which can originate from the solar wind or a high-altitude nuclear explosion, have the potential to damage satellites in low-Earth orbit. For example, in 1962, the US detonated the Starfire warhead at an altitude of about 400 km. The unexpected resulting enhancement of the radiation belts disabled several satellites within a few months and energetic electrons remained trapped in the radiation belts for up to several years. In order to address this potential vulnerability, schemes have been proposed to drain electrons from the radiation belts, with the most promising based on using high-power RF waves to couple to the trapped electrons. This talk will provide an overview of radiation belt remediation including the use of electron accelerators to drive these RF waves.  
slides icon Slides FRYGB2 [1.314 MB]  
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