A Polarized Electron RF Photoinjector Using the Plane-Wave-Transformer (PWT) Design

Polarized electron beams are now in routine use in particle accelerators fornuclear and high energy physics experiments. These beams are presently producedby dc-biased photoelectron sources combined with rf chopping and bunchingsystems with inherently high transverse emittances. Low emittances can beproduced with an rf gun, but the vacuum environment has until now beenconsidered too harsh to support a negative electron affinity GaAs photocathode.We propose to significantly improve the vacuum conditions by adapting a PWT rfphotoinjector to achieve reasonable cathode emission rates and lifetimes. Thisadaptation can also be combined with special optics that will result in a flatbeam with a normalized rms emittance in the narrow dimension that may be as lowas 10-8 m.