Laser system for a high duty cycle photoinjector

Abstract

We have developed a solid-state laser system that produces a 1 MHz pulse train of 800 equal amplitude pulses with 25 μJ per pulse at λ=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 λ=263 nm and transport losses, 5 μJ per pulse of UV are available at the Cs 2Te 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.