  The high intensity polarized electron source is a critical component for
future nuclear physics facilities. The Electron Ion Collider (EIC) requires a
polarized electron gun with higher voltage and higher bunch charge compared to
any existing polarized electron source. At Brookhaven National Laboratory, we
have built an inverted high voltage direct current (HVDC) photoemission gun
with a large cathode size. We report on the performances of GaAs photocathodes
in a high gradient with up to a 16 nC bunch charge. The measurements were
performed at a stable operating gap voltage of 300 kV - demonstrating
outstanding lifetime, and robustness. We observed obvious lifetime enhancement
by biasing the anode. The gun also integrated a cathode cooling system for
potential application on high current electron sources. The various novel
features implemented and demonstrated in this polarized HVDC gun open the door
towards future high intensity-high average current electron accelerator
facilities.
