Non-inductive formation of spherical tokamak plasmas by ECH on CPD

Non-inductive plasma current generation and the resultant formation of closed magnetic surfaces have been achieved by electron-cyclotron-heating (ECH) in the compact plasma-wall-interaction experimental device (CPD). The rapid increase of plasma current called 'current jump', which connects externally applied open-field configuration with closed-field equilibrium, has been observed under relatively high vertical fields. By comparing normal X-mode injection and co-directional O-mode injection, the critical currents, at which current jump starts and stops, are found to be independent of the incident wave mode. However, under open-field configuration before the current jump, co-directional O-mode is more effective than normal X-mode in generating plasma currents. (author)