A MULTILASER SYSTEM FOR A FAST SAMPLING THOMSON SCATTERING DIAGNOSTIC

A multilaser system is being developed for the DIII-D Thomson scattering diagnostic. This system combines the beams from up to 8 Nd:YAG lasers onto a common beamline in which the beams are nearly parallel and are all focused into a small, common area within the desired scattering volume. Each laser can be fired at a constant rate (20 Hz per laser) for a high average repetition rate, or together in a "burst," which will give very high sampling rates (10-20 kHz) for short periods. The burst mode will be triggerable by plasma events, which will allow for study of transient phenomena, but will require nonperiodic firing of the lasers. Beamline diagnostics include position sensitive detectors for computer controlled feedback alignment of the 35 m beamline, an image position detection system for monitoring the alignment of the collection lens to the scattering volume, and a 1-D reticon camera for divergence monitoring. The effects of the nonperiodic firing of the lasers will be monitored with the reticon camera.