High-Density Current Injection to Magnetically Confined Plasmas with a Miniature Plasma Source

Influences of high-density current injection with a miniature plasma source on a reversed-field pinch (RFP) have been studied in the Separatrix Test Experiment-2 (STE-2) device. The current injector has successfully produced a unidirectional field-aligned electron beam. No deterioration or slight improvement of the RFP discharge was observed with injection of poloidal current of up to 1 kA. The deepening of the local edge toroidal magnetic field reversal has been observed in the vicinity of the injection port. The global change in the current profile and the stabilization of m=1 tearing modes will require current injection at multiple toroidal locations with a higher bias voltage. However, the gas throughput from the injector is too high, hindering the addition of more injectors in the STE-2 device. Global current profile control experiments with multiple miniature plasma sources are expected in larger devices.