Real time control system for the National Spherical Torus Experiment (NSTX)

The NSTX is a new national facility for the study of plasma confinement, heating, and current drive in a low aspect ratio, spherical torus (ST) configuration. The ST configuration is an alternate magnetic confinement concept which is characterized by high β (ratio plasma pressure to magnetic held pressure) and low toroidal field compared to conventional tokamaks, and could provide a pathway to the realization of a practical fusion power source. The NSTX depends on a real time, high speed, synchronous, and deterministic control system acting on a system of thyristor rectifier power supplies to 1) establish the initial magnetic field configuration; 2) initiate plasma within the vacuum vessel; 3) inductively drive plasma current; and 4) control plasma position and shape