Recent Progress at SLAC Extracting High Charge from Highly-Polarized Photocathodes for Future-Collider Applications

Technical Report · Tue Jan 20 04:00:00 EST 2004

DOI:https://doi.org/10.2172/826692· OSTI ID:826692

Clendenin, J ^[1]

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1. SLAC

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 ({ge}10{sup 19} cm{sup -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 hour 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.

• Research Organization: Stanford Linear Accelerator Center, Menlo Park, CA (US)
• Sponsoring Organization: USDOE Office of Science (US)
• DOE Contract Number: AC03-76SF00515
• OSTI ID: 826692
• Report Number(s): SLAC-PUB-10304
• Country of Publication: United States
• Language: English

Related Subjects

08 HYDROGEN
43 PARTICLE ACCELERATORS
CATHODES
CLEANING
DEPOLARIZATION
HYDROGEN
PHOTOCATHODES
STANFORD LINEAR ACCELERATOR CENTER
SUPERLATTICES