High voltage dc gun for high intensity polarized electron source

The high intensity polarized electron source is a critical component for future nuclear physics facilities. The electron-ion collider 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 performance of GaAs photocathodes in a high gradient with up to 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 will open the door toward future high intensity-high average current electron accelerator facilities.