Self-Organization Process with Dynamo Activity in Ultra-Low q and Reversed-Field-Pinch Plasmas

Abstract

Dynamo activity is highly important for formation and confinement of ultra-low q (ULQ) and reversed-field-pinch (RFP) plasmas. These configurations are self-organized by a spontaneous dynamo electric field. In order to investigate the properties of this self-organization process, an inductive poloidal electric field is applied to standard ULQ and RFP plasmas. Synchronized to the application of poloidal electric fields, remarkable responses of plasma parameters are observed. In the ULQ experiment, toroidal plasma current increases with decrease in loop voltage. In this experiment, fluctuation levels are almost constant. On the other hand, dIp/dt decreases with the reduction of plasma fluctuations in the RFP experiment. In these processes, plasmas will self-organize to maintain a state of nearly minimum energy. In general, the self-organization process changes the total dissipation in the system through the enhancement of the plasma fluctuation. To improve the plasma confinement for ULQ and RFP plasmas, it is important to understand the properties of this self-organization process in detail.