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Open Access Publications from the University of California

Comparative study of active plasma lenses in high-quality electron accelerator transport lines

  • Author(s): Van Tilborg, J
  • Barber, SK
  • Benedetti, C
  • Schroeder, CB
  • Isono, F
  • Tsai, HE
  • Geddes, CGR
  • Leemans, WP
  • et al.

Published Web Location Commons 'BY-NC-ND' version 4.0 license

© 2018 Author(s). Electrically discharged active plasma lenses (APLs) are actively pursued in compact high-brightness plasma-based accelerators due to their high-gradient, tunable, and radially symmetric focusing properties. In this manuscript, the APL is experimentally compared with a conventional quadrupole triplet, highlighting the favorable reduction in the energy dependence (chromaticity) in the transport line. Through transport simulations, it is explored how the non-uniform radial discharge current distribution leads to beam-integrated emittance degradation and a charge density reduction at focus. However, positioning an aperture at the APL entrance will significantly reduce emittance degradation without additional loss of charge in the high-quality core of the beam. An analytical model is presented that estimates the emittance degradation from a short beam driving a longitudinally varying wakefield in the APL. Optimizing laser plasma accelerator operation is discussed where emittance degradation from the non-uniform discharge current (favoring small beams inside the APL) and wakefield effects (favoring larger beam sizes) is minimized.

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