SLC polarized beam source electron optics design

A description is presented of the design of the beam-line from the polarized electron gun to the linac injector in the Stanford Linear Collider (SLC). The polarized electron source is a GaAs photocathode, requiring 10/sup -11/-torr-range pressure for adequate quantum efficiency and longevity. The photocathode is illuminated by 3-ns-long laser pulses. The quality of the optics for the 160-kV beam is crucial since electron-stimulated gas desorption from beam loss in excess of 0.1% of the 20-nC pulses may poison the photocathode. The authors' design for the transport line consists of a differential pumping region isolated by a pair of valves.<
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