Speaker
Description
Highly spin-polarized electron beams for accelerators are almost universally generated by laser-driven, DC-biased photoelectron sources containing GaAs-based photocathodes. These sources are subject to damage mechanisms causing the gradual destruction of the photocathode surface at a rate at least proportional to the beam current, effectively limiting the achievable average current for a given continuous operating time. As the ongoing development of polarized, high-current electron machines and positron conversion targets is pushing the average current requirements beyond what has been reliably demonstrated, Jefferson Lab is pursuing R&D efforts to greatly increase the lifetime of photoelectron sources. Employing a combination of strategies such as deflecting fields for ions, optimized laser profiles, and photocathode materials with enhanced optical absorption, we hope to achieve a tenfold increase in the available average current. In this talk, I will give an overview of the ongoing activities, recent progress made, and the remaining challenges.