Operation of a multiple laser trigger system on the Z facility

Abstract

A new laser trigger system (LTS) has been installed on the Z accelerator. The new system is based on 36 individual quadrupled-Nd:YAG lasers with 35mJ, 3ns wide pulses, and replaces the pre-existing single, large 4J KrF excimer. The new LTS is designed for shaping current pulses at the load by individually triggering each module on Z. Laser alignment into the gas switches is accomplished via the green, second-harmonic leakage and a simple array of 36 inexpensive CCD cameras and reflective targets behind turning mirrors. The green alignment method has increased target visibility, improving alignment accuracy. A modular approach has been implemented to minimize maintenance downtime. Individual items such as mirrors, mounts, motors, cameras, lasers, and photo detectors are standard, off-the-shelf components. Quick replacement of malfunctioning parts is essential to maintaining Z's stringent shot schedule. A single computer system allows for pre-shot laser alignment and characterization from a remote location that might be the operator's home computer. In the event of component failures close to shot time, the control system will indicate what the failure is for rapid troubleshooting and replacement. The new LTS can compensate for timing drifts in pulse power components, particularly runtime trends of the gas switches, reducing the need to drain the water section for optic replacements, and providing a significant improvement for Z's performance, maintenance, and reliability.