Running experience with the laser system for the RF gun based injector at the TESLA Test Facility linac

During the run 1998/1999, the new injector based on a laser driven RF gun w as brought into operation at the TESLA Test Facility Linac (TTFL) at DESY. A key element of the injector is the laser system to illuminate the RF gun cathode to produce short (ps) electron bunches of high charge (nC). This el ectron beam is used to perform various experiments for the future TESLA lin ear collider, and to drive the free electron laser TTF-FEL. The laser desig n is challenged by the unusual requirement of providing synchronized ps UV pulses in 0.8 ms long trains with ambitious stability requirements. The des ign was also driven by the requirement to have an operational system with a high reliability. The system is based on a mode locked solid-state (Nd:YLF ) pulse train oscillator followed by a linear amplifier chain. In a first p hase, a laser pulse rate of 1 MHz within the train has been realized, 2.25 MHz and 9 are in preparation. Performance and running experiences with the laser system during the last TTF run are reported. (C) 2000 Elsevier Scienc e B.V. All rights reserved.