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In this work, we investigate multiple heat cleaning options for MOCVD-grown photocathodes containing a distributed Bragg reflector and a strained GaAs/GaAsP superlattice. This was done using a microMott polarimeter[1] at Jefferson Lab to optimize both quantum efficiency and polarization. Polarized photocathodes are essential to perform the physics programs planned at Jefferson Lab and Brookhaven National Lab. The fabrication process for MOCVD-grown photocathodes does not allow for the inclusion of an arsenic cap, contrarily to what is done in MBE-grown photocathodes[2]. Without proper preparation, photocathode performance is limited due to surface contamination which requires an optimized cleaning procedure. Here, we varied both duration and temperature of the heat cleaning process and observed increased quantum efficiency with negligible loss of polarization. Results of the optimized cleaning process in addition to upgrades to the testing apparatus will be presented.
[1] J. McCarter, M. Stutzman, K. Trantham, T. Anderson, A. Cook, T. Gay, "A low-voltage retarding-field Mott polarimeter for photocathode characterization", Nuclear Instruments and Methods in Physics Research Section A: Accelerators, Spectrometers, Detectors and Associated Equipment 618 (1) (2010)
[2] R. Bernstein, A. Borg, H. Husby, B.O. Fimland, J. Grepstad, "Capping and capping of MBE grown GaAs(001), Al$_{0.5}$Ga$_{0.5}$As(001), and AlAs(001) investigated with ASP, PES, LEED, and RHEED", Applied Surface Science 56-58 (1992)
