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Open Access Publications from the University of California

Nonuniform discharge currents in active plasma lenses

  • Author(s): Van Tilborg, J
  • Barber, SK
  • Tsai, HE
  • Swanson, KK
  • Steinke, S
  • Geddes, CGR
  • Gonsalves, AJ
  • Schroeder, CB
  • Esarey, E
  • Bulanov, SS
  • Bobrova, NA
  • Sasorov, PV
  • Leemans, WP
  • et al.

© 2017 authors. Published by the American Physical Society. Active plasma lenses have attracted interest in novel accelerator applications due to their ability to provide large-field-gradient (short focal length), tunable, and radially symmetric focusing for charged particle beams. However, if the discharge current is not flowing uniformly as a function of radius, one can expect a radially varying field gradient as well as potential emittance degradation. We have investigated this experimentally for a 1-mm-diameter active plasma lens. The measured near-axis field gradient is approximately 35% larger than expected for a uniform current distribution, and at overfocusing currents ring-shaped electron beams are observed. These observations are explained by simulations.

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