Physical Review Special Topics. Accelerators and Beams (Aug 2006)

Radial bunch compression: Path-length compensation in an rf photoinjector with a curved cathode

  • M. J. de Loos,
  • S. B. van der Geer,
  • Y. M. Saveliev,
  • V. M. Pavlov,
  • A. J. W. Reitsma,
  • S. M. Wiggins,
  • J. Rodier,
  • T. Garvey,
  • D. A. Jaroszynski

DOI
https://doi.org/10.1103/PhysRevSTAB.9.084201
Journal volume & issue
Vol. 9, no. 8
p. 084201

Abstract

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Electron bunch lengthening due to space-charge forces in state-of-the-art rf photoinjectors limits the minimum bunch length attainable to several hundreds of femtoseconds. Although this can be alleviated by increasing the transverse dimension of the electron bunch, a larger initial radius causes path-length differences in both the rf cavity and in downstream focusing elements. In this paper we show that a curved cathode virtually eliminates these undesired effects. Detailed numerical simulations confirm that significantly shorter bunches are produced by an rf photogun with a curved cathode compared to a flat cathode device. The proposed novel method will be used to provide 100 fs duration electron bunches for injection into a laser-driven plasma wakefield accelerator.