Superconducting RF Photocathode Gun for Low Emittance Polarized ELectron Beams

A radio frequency (RF) photoemission source that delivers polarized electrons at low emittance would be an attractive electron source for a linear collider. Moreover, it has been demonstrated recently that such a source, in conjunction with nearby injection-system optics, can deliver a beam with a high ratio of transverse emittances, leading to a simplification or elimination of a linear collider¿s electron damping system. However, at present, RF electron gun technology has not developed sufficiently to assure that such a source is feasible, mainly due to issues involving the residual vacuum level. This project will develop a long-life, low-emittance photocathode source for producing polarized electrons. Phase I will explore the feasibility for developing a source that has an acceptable lifetime, low emittance, and a large ratio between vertical and horizontal emittance. This combination will require a substantial improvement of the vacuum inside the RF source, which will be achieved using a superconducting gun cavity. A solenoid will be incorporated into this gun to provide the magnetized beam necessary to transform the beam into a high transverse emittance ratio beam. Commercial Applications And Other Benefits as described by the Applicant: All linear collider designs should benefit from long-life, low-emittance polarized sources. If the emittance from the source could be made low enough, the need for an electron damping ring would be eliminated, resulting in substantial cost and real estate savings. In addition to the application for high energy physics, such a source also would have application to nuclear physics accelerators.