Optical bunching of relativistic electrons for injection into a GeV plasma beatwave accelerator

A proposed GeV plasma beatwave accelerator (PBWA) requires a high power 1 /spl mu/m laser running on two frequencies. The vacuum interaction between such a laser and a relativistic electron beam is one mechanism whereby the electrons can be bunched such that when injected into the PBWA they occupy only small regions of phase situated at the peaks of the accelerating field. This is exactly what is required to obtain a high quality beam from the accelerator. We outline the details of this scheme.