Feedback-controlled particle suspension system for LITE magnetic mirror fusion facility

Abstract

A feedback-controlled particle suspension system has been developed for laser target plasma production in the LITE experiment. Suspension voltages derived from position and velocity (position derivative) feedback signals serve to capture an injected particle in high vacuum, damp the particle motion, and stably position the particle at the system null. In typical operations, LiH particles of ∼100-μm diameter, projected by a spring plunger into the suspension region, are captured and positioned at the system center in ⩽0.25 sec with a jitter of ⩽20 μm, less than 1/5 the particle diameter. With this system the precise particle positioning required for spherically symmetric plasma generation is obtained even with large particle sizes, and the feedback particle suspension system is incorporated as an integral part of the LITE experimental facility for studies of neutral injection buildup on a dense, mirror-confined, laser-produced target plasma.