Laser system for a high duty cycle photoinjector

We have developed a solid-state laser system that produces a 1 MHz pulse train of 800 equal amplitude pulses with 25 mu J per pulse at lambda = 1054 nm; the repetition rate is 1 Hz. The laser pulse train is produced by a mode-locked Nd:YLF oscillator, synchronized to the phase of the photoinjector RF. The pulses are amplified in a Nd: glass multipass amplifier followed by a two-pass amplifier. The laser system uses chirped pulse amplification to produce 2 ps pulses. After two stages of second harmonic generation to lambda = 263 nm and transport losses, 5 mu J per pulse of UV are available at the Cs,Te photocathode of the RF gun. The photocathode quantum efficiency is in the 2-6% range, and electron bunches with charge in excess of 10 nC have been extracted during photoinjector operation. (C) 1999 Elsevier Science B.V. All rights reserved.