Abstract

The recent development of compact high-peak-power lasers has spurred renewed interest in electron acceleration by the use of the ultrahigh-electric-field gradients of laser-driven plasma waves [1]. In fact, the field gradient of a plasma wave has recently been demonstrated to exceed that of an RF linac by four orders-of-magnitude (E ≥ 200 GV/m) and has been used to accelerate electrons with over 1-nC of charge per bunch in a low-emittance beam (1 mm-mrad) [2]. However, the energy spread of such beams is 100%, due to the method of injection, which is self-trapping of background electrons with random phases with respect to the accelerating buckets. In order to reduce this energy spread, it is generally thought that the required pre-acceleration can only be accomplished with a conventional RF linac. The difficulty is that the wakefield accelerating buckets are 30 fs in duration and the injection bunch must be a small fraction of that. The shortest pulses from laser-triggered photocathode RF guns are much longer, currently 0.5 ps in duration, and have jitters of more than a picosecond. Besides, RF linacs are large and expensive.

© 1997 Optical Society of America