Electron Micro‐Bunch Generation from RF Photoinjectors

In this paper we discuss how the injector specifications of a 2nd‐generation plasma beat wave accelerator (PBWA) experiment can be achieved by a photo‐injector. Typical required bunch lengths (FWHM) are 50 microns with 15 pC bunch charge. We analyze the possibility of generating such short electron bunches directly from a photoinjector by illuminating a photocathode in an RF electron gun with a phase‐locked 160‐fs laser pulse. In particular, we address all de‐bunching effects taking place during acceleration and transport through the photo‐injector. We provide a set of analytical scaling laws, as well as a comparison with detailed simulations of the beam dynamics. The possible performances of the present SATURNUS linac setup are presented, as well as the anticipated capabilities of a multi‐cell RF gun structure based on the PWT linac presently in operation at UCLA.