A Continuous Wave, Normal Conducting, L-band PWT Polarized Photoelectron Gun

Several current and proposed particle accelerator projects for nuclear physics research require a polarized electron source capable of producing an electron beam with 85% polarization. The current design of the polarized electron injector is based on a dc gun with buncher and capture sections, followed downstream by a cryomodule for pre-acceleration into the main linac. This project will develop technology to replace the dc gun and bunchers with an L-band, normal-conducting, polarized electron gun of Plane-Wave-Transformer (PWT) design. The PWT gun will be designed to operate under the ultra-high vacuum (UHV) needed to assure the survivability of the gallium arsenide (GaAS) photocathode used to produce the electron beam. An effective cooling system will remove the heat generated by the high-power continuous-wave RF source for the gun. In Phase I, a baseline PWT gun design will be developed. In Phase II, the L-band PWT photoelectron gun will be built, integrated with a GaAs photocathode, and tested to demonstrate the survivability of the GaAs photocathode in UHV. Commercial Applications and other Benefits as described by the awardee: The successful demonstration of an L-band PWT gun as a viable polarized electron source would open the market for applications to current and future accelerator projects that require a GaAs photocathode. In other applications, the GaAs PWT gun could be used as a high brightness electron injector for non-polarized electron linear accelerators, synchrotrons, free electron lasers, and other light sources. In combination with a high-intensity laser, the PWT gun could be a Compton source for the production of ultrafast, copious X-rays for applications in biotechnology, medicine, industry, and research.