Generation of high heat flux plasmas by high power rf heating in the divertor plasma simulator NAGDIS-II

High-power rf heating in the ion cyclotron range of frequency (ICRF) has been carried out in a divertor plasma simulator NAGDIS-II. The main objective of the present work is to produce high heat flux plasmas for fundamental studies of the divertor plasmas in magnetically confined fusion devices. Waves are excited by phased-loop antenna array in a frequency range between 0.5 and 1.5 MHz. Inverter power supplies using static induction transistors (SIT) are employed to excite ion cyclotron slow waves. In NAGDIS-II a target plasma for rf heating is produced by TP-D-type de discharges, where the electron density is n(e) < 6 x 10(19) m(-3), and the electron and ion temperature are T-e = 5-10 eV and Ti = 1-10 eV in helium plasmas, respectively. By injecting about 14 kW rf power we have obtained high heat flux plasmas with n(e) = 2 x 10(19) m(-3), T-e similar to 20 eV and T-i similar to 18 eV so far. The plasma heat flux into the end plate is measured by calorimetric method and the power balance of the rf heated plasmas is studied experimentally. (C) 2000 Published by Elsevier Science Ltd.