Characteristic performance of the ICRF heating in the divertor plasma simulator NAGDIS-II

Summary form only given. This paper presents a experiment about high beat flux plasma generation with ICRF heating in the linear divertor simulator NAGDIS-II. Main objectives of present work is to produce high heat flux plasmas for divertor plasma simulation experiment. In NAGDIS-II, plasmas are produced by DC discharge. The source gas of the plasma is He and the plasma parameter before heating is ne-3E/spl sim/10/sup 19//m/sup 3/, Te<10eV and Ti=4-6eV. Two inverter power supplies using static induction transistor(SIT) are employed to excite the ion cyclotron slow waves in the plasma. Each power supply can generate the RF power of about 15kW in CW mode at 0.25-1.7MHz. Waves are excited by phased loop antenna array. In the previous experiment (Imai et al., 2000), we had a result that about 45% of the injected power is lost at the antenna through the formation of the RF induced sheath and about 35% of the injected power is lost to the chamber wall through the ion-neutral interaction(charge exchange and elastic collision). As a result, the increase of heat load at the end plate is only 5-10% of the injected power. The heat load is measured by the calorimetric method. The reduction of the RF power loss due to RF induced sheath and ion-neutral collisions is necessary to improve the heating efficiency. Reduction of the loss at the antenna is expected by keeping the antenna away from the plasma to reduce the plasma density near the antenna. The ion neutral collision loss can be reduced by decreasing the neutral pressure. Under the low neutral pressure condition, the ion temperature increases. The heat load at the antenna is reduced drastically. As a result, the heat load concentrate on the end plate. We will try to produce higher heat flux plasma in NAGDIS-II.