Preionization and start-up in the ISX-B Tokamak using electron cyclotron heating at 28 GHz

A 28-GHz gyrotron was used to produce a plasma at the electron cyclotron resonance in the impurity study experiment (ISX-B) Tokamak. The influence of the toroidal magnetic field magnitude, error fields, gas pressure, microwave power, microwave pulse length, and microwave timing was studied for experiments with magnetic field and gas only. Experiments with preionization followed by capacitor discharges were carried out in which these quantities were varied, as were the capacitor bank voltages. Optimum conditions of preionization for some of the parameters were determined. A theoretical model that adequately reproduces the data is given. The temporal evolution of the electron temperature and density, the neutral density, and the plasma current are shown with the model.