Advancing Plasma Control on the Princeton Beta Experiment Modification

A digital plasma control system for the Princeton Beta Experiment Modification (PBX-M) is being prepared. The functions of the existing analog shape and position control subsystems will be assumed by the upgraded control system. Plasma profile control will be pursued by making use of the lower hybrid current drive and the ion Bernstein wave heating systems to modify the plasma current and pressure profiles. A framework for integrating these plasma control functions is presented. Existing profile diagnostics can, with some modification, provide the information necessary to feed back on the plasma profiles. The digital control hardware is commercially available. Four real-time processors, which can be programmed independently, reside on a single Versa Module Eurocard board with dedicated shared memory. The parallel programming capability allows the separation by function of the vertical position control, shaping control, and profile control, which have different characteristic time-scales.