Speaker
Description
Polarized electron sources are essential for accelerator facilities such as the Electron–Ion Collider and polarized positron sources, which require guns with higher voltage and bunch charge than existing polarized gun. At Brookhaven National Laboratory, we developed an inverted High-Voltage DC (HVDC) polarized photoemission gun with a Distributed Bragg Reflector superlattice GaAs photocathode and a cathode cooling system suited for future high-current operation. The gun was conditioned to 350 kV with no measurable field emission and delivered polarized electron bunch charges up to 11.6 nC, reaching the current density of 14.5 A/cm² at the source. To our knowledge, this is a record operating voltage for a polarized DC gun and a record current density for a polarized electron source. We mitigated the surface charge limit through optimized surface doping and heat-cleaning procedures and by leveraging the high accelerating gradient at the cathode. We also studied the effects of the DBR layer and laser parameters on photocathode lifetime and identified an operating regime that provides long lifetime while maintaining high polarization at 30 µA.
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