Development of a Polarized Electron Gun Based on an S-band Pwt Photoinjector*

An RF polarized electron gun utilizing the unique features of an integrated, plane-wave-transformer (PWT) photoelectron injector [1] is being developed by DULY Research Inc. in collaboration with SLAC. Modifications to a DULY S-band device [2] include: a re-design of the photocathode/RF backplane interface to accommodate a GaAs cathode; change in the design of the vacuum ports to provide 10 Torr operation; the inclusion of a loadlock photocathode replacement system to allow for reactivation and cesiation of the GaAs photocathode in a vacuum; and alteration of the magnet field coils to make room for the load-lock. The use of a stainless steel outer tank and cooling rods without copper plating may also provide better vacuum performance at the expense of diminished Q-factor. The effectiveness of both the standard cooling rods and synthetic diamond heat sinks for disk cooling is investigated for future linear collider applications operating at a rep rate of 180 Hz and a bunch charge of 2 nC.