A proposed superconducting photoemission source of high brightness

Abstract

We describe the design of an electron injector for the production of a bunched cw electron beam of high brightness, low energy spread, and potentially high beam power. Electron beams of this kind are required for high efficiency and short wavelength free electron lasers. The injector consists of a superconducting reentrant cavity housing a photoemission cathode evaporated on a superconducting substrate. The cathode is illuminated with short light pulses of a mode-locked frequency doubled Nd: YAG laser. The experimental layout of the "superconducting photoemission source" is described together with its components: the photocathode preparation chamber, the cavity, the cryogenic setup, and the beam analysis system. The conceptual beam parameters are discussed and first results of calculations on beam dynamics using a particle-in-cell computer code are given. © 1989.