An Ultra-Low-Emittance, L-Band, Flat-Beam PWT Photoinjector

The International Linear Collider (ILC), which is to be built in the next decade, requires an electron injector that provides a highly polarized beam with high brightness. Current dc-gun-based, polarized electron sources cannot achieve the low emittance required by the ILC, and a complicated and expensive damping ring is required for this purpose. This project will develop technology, based on an oscillation-free klystron concept, to achieve ultra-low emittance. The oscillation barrier in short-wavelength klystrons will be broken by solving the problems of coupling, parasitic mode damping, and mode separation in a non-relativistic, high-power klystron. In Phase I, feasibility will be demonstrated by performing two experiments. The first will demonstrate that an activated GaAs photocathode could survive in the radio frequency cavity. The second will show that an ultra-low vertical emittance could be achieved with a high-aspect-ratio flat beam. A detailed simulation and design of a 1.3 GHz, 1+2/2 cell, photoinjector will be performed. Commercial Applications And Other Benefits as described by the Applicant: The technology should provide an order-of-magnitude improvement in the performance of electron photoinjectors, which are needed for experiments related to the fundamental physics of elementary particles, solid-state/semiconductor physics, and surface physics. The photoinjector would be an attractive candidate as an ILC polarized electron injector, due to its low cost, ease of fabrication, and exceptional robustness.