Schematic view of the photocathode setup of the Heidelberg TSR electron target.
Photoelectron QE vs photon energy for a GaAs surface which is chemically treated by HCl (1), cleaned by AH treatment (2), activated by Cs and subsequently heat cleaned (3), fully activated by (Cs,O) with subsequent heat cleaning after degradation [(4)–(6)] and recleaned by AH (7) with an exposure dose of .
QE ultraviolet spectra from a degraded cathode after heat cleaning (1) and after subsequent AH cleanings with AH exposures of (2), (3), (4), (5), (6), and (7).
Long-time evolution of QE of two photocathodes. The plot shows the QE obtained by (Cs,O)-activation after each AH cleaning procedure vs integrated AH dose. Two typical samples from different groups, grown by LPE (blue squares) and by MOCVD (red circles), were used. The thick dashed arrow indicates the moment when cleaning with HCl solution in the glovebox was applied to the MOCVD cathode. The two thin arrows indicate small rises of QE folowing AH treatment of higher-than-average dose intensity of about .
Photoluminescence images of “fresh” MOCVD-photocathode surface and at the end of its operation lifetime.
Surface exposure rates and underlying key parameters of the capillary AH source used for cleaning of a diameter photocathode located away from the capillary outlet. The temperature of the capillary is fixed to .
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