Novel pulse train glass laser for RF photoinjectors

First developed a decade ago, the laser-driven RF photoinjector has become a reliable source for high brightness and low emittance electron beams. Advanced applications of photoinjectors have placed increasingly challenging demands on the photocathode excitation lasers. Typical requirements include high peak power, short pulse length, low timing jitter, stable amplitude, short wavelength, and reliable long-term operation. The photoinjector for the superconducting accelerator at the TESLA Test Facility (TTF) makes all of these demands, and also presents the novel requirement to generate long pulse trains of narrowly spaced micropulses. A collaboration between the University of Rochester, Fermilab, and UCLA has been formed to produce a state-of-the-art RF photoinjector and laser system to meet the unique requirements for the TTF.; We report on the design and performance of a new laser designed for photocathode excitation in an RF photoinjector with the TTF beam requirements. The laser uses a mode-locked Nd:YLF oscillator and a sequence of unsaturated Nd:glass amplifiers in a chirped-pulse amplification scheme to produce a 1 MHz pulse train of 800 pulses. An unsaturated multipass amplifier provides the initial gain, and a two-pass rod amplifier and five-pass zig-zag slab amplifier will provide up to 1 mJ per pulse. To compensate for the time variation in the gain of the amplifiers over duration of the pulse train, an input pre-shaping scheme is used to flatten the output envelope.; Rugged, high quantum efficiency photocathodes are required for photoinjector applications. We report measurements of the quantum efficiency of eight photocathode materials and consider their application to the development of superconducting RF photoinjectors.; With the availability of a high brightness electron beam and high power lasers at Fermilab, we propose to produce tunable, narrow bandwidth, picosecond bursts of x-rays by backscattering intense laser pulses from the electron beam. Other proposals have been made to pursue advanced accelerator research at this high brightness electron facility.