Recent progress at SLAC extracting high charge from highly polarized photocathodes for future-collider applications

J. E. Clendenin, A. Brachmann, E. L. Garwin, S. Harvey, J. Jiang, R. E. Kirby, D. A. Luh, T. Maruyama, R. Prepost, C. Y. Prescott, J. L. Turner

Research output: Contribution to journalConference articlepeer-review

9 Scopus citations

Abstract

Future colliders such as NLC and JLC will require a highly polarized macropulse with charge that is more than an order of magnitude beyond that which could be produced for the SLC. The maximum charge from the SLC uniformly doped GaAs photocathode was limited by the surface charge limit (SCL). The SCL effect can be overcome by using an extremely high (≥1019cm-3) surface dopant concentration. When combined with a medium dopant concentration in the majority of the active layer (to avoid depolarization), the surface concentration has been found to degrade during normal heat cleaning (1 h at 600°C). The Be dopant as typically used in an MBE-grown superlattice cathode is especially susceptible to this effect compared to Zn or C dopant. Some relief can be found by lowering the cleaning temperature, but the long-term general solution appears to be atomic hydrogen cleaning.

Original languageEnglish
Pages (from-to)308-311
Number of pages4
JournalNuclear Instruments and Methods in Physics Research, Section A: Accelerators, Spectrometers, Detectors and Associated Equipment
Volume536
Issue number3
DOIs
StatePublished - 11 Jan 2005
EventPolarized Sources and Targets for the 21st Century - Novosibirsk, Russian Federation
Duration: 22 Sep 200326 Sep 2003

Keywords

  • Photocathodes
  • Photoemission
  • Semiconductors
  • Surface charge limit

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