Large area electron beam generation and propagation for KrF lasers

High energy KrF lasers have optical output apertures ranging from 10×10 cm2 to 1×1 m2. The electron beam must uniformly pump the entire aperture and the length of the laser amplifier. These electron beams are usually mildly relativistic (250-750 keV) and have moderate current densities (10-100 amps/cm2). The NIKE system at NRL incorporates a 20×20 cm2 aperture laser amplifier to drive a 60×60 cm2 aperture final amplifier expected to deliver greater than 4 kJ of laser output. Design considerations, testing, and experimental data from the 20 cm amplifier are presented as well as an overview of some of the models used to understand the results. Particular attention is paid to obtaining a uniform electron beam with minimal small scale structure. Results of the electron beam uniformity and improved electron transmission efficiency to the gas for the 20 cm amplifier will be presented. The design of the 60 cm amplifier being constructed will also be presented.