FEEDBACK-STABILIZED ND-YLF AMPLIFIER SYSTEM FOR GENERATION OF PICOSECOND PULSE TRAINS OF AN EXACTLY RECTANGULAR ENVELOPE

We describe the amplifier chain of the photocathode laser of the TESLA Test Facility. This chain is optimized for amplification of trains of picosecond pulses. At its output, pulse trains with a rectangularly s haped envelope of 0.7% flatness and a longterm stability of the energy in the individual picosecond pulses in excess of 0.9% are obtained, T his stability is achieved by using a computerized feedback control sys tem, which we describe in detail together with the versatile feedback algorithm applied. The feedback loop performs st tight adjustment of b oth the shape and magnitude of the flashlamp pulses as well as the sta rting time of the primp with respect to the pulse train. High-current insulated gate bipolar transistors are used to directly manipulate the flashlamp current in a microsecond time scale.