Electron-Cyclotron Resonance Preionization and Heating in the Proto-Cleo Torsatron

ECR-breakdown and heating in a bifurcated torsatron topology are investigated with extra-ordinary mode injection from the high-field side (7.2 GHz/2 KW/10 ms). The breakdown characteristics are explained by stochastic heating enhanced by helical ripple effects. In the quasi-stationary regime (0.01n(,cr) < n < 0.6 n(,cr)), two-dimensional plasma profiles indicated heating inhomogeneities associated with RF power absorption near the UHR layer. The production of a suprathermal electron population, at the outer plasma edge, was indicated by non-thermal microwave emission and target SXR emission.