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Title: Tailored electron bunches with smooth current profiles for enhanced transformer ratios in beam-driven acceleration

Collinear high-gradient O(GV/m) beam-driven wakefield methods for charged-particle acceleration could be critical to the realization of compact, cost-efficient, accelerators, e.g., in support of TeV-scale lepton colliders or multiple-user free-electron laser facilities. To make these options viable, the high accelerating fields need to be complemented with large transformer ratios >2, a parameter characterizing the efficiency of the energy transfer between a wakefield-exciting “drive” bunch to an accelerated “witness” bunch. While several potential current distributions have been discussed, their practical realization appears challenging due to their often discontinuous nature. In this paper we propose several alternative continuously differentiable (smooth) current profiles which support enhanced transformer ratios. We especially demonstrate that one of the devised shapes can be implemented in a photo-emission electron source by properly shaping the photocathode-laser pulse. We finally discuss a possible superconducting linear-accelerator concept that could produce shaped drive bunches at high-repetition rates to drive a dielectric-wakefield accelerator with accelerating fields on the order of ~60 MV/m and a transformer ratio ~5 consistent with a recently proposed multiuser free-electron laser facility.
 [1] ;  [2]
  1. Northern Illinois Univ., DeKalb, IL (United States)
  2. Fermi National Accelerator Lab. (FNAL), Batavia, IL (United States)
Publication Date:
Grant/Contract Number:
SC0011831; AC02-07CH11359; HDTRA1-10-1-0051
Published Article
Journal Name:
Physical Review Special Topics. Accelerators and Beams
Additional Journal Information:
Journal Volume: 18; Journal Issue: 8; Journal ID: ISSN 1098-4402
American Physical Society (APS)
Research Org:
Fermi National Accelerator Lab. (FNAL), Batavia, IL (United States)
Sponsoring Org:
USDOE Office of Science (SC), High Energy Physics (HEP) (SC-25)
Country of Publication:
United States
OSTI Identifier:
Alternate Identifier(s):
OSTI ID: 1213569