HIGH-POWER ION-CYCLOTRON RANGE OF FREQUENCY HEATING IN A COMPACT HELICAL SYSTEM

The ion cyclotron range of frequency (ICRF) heating experiment with tw o half-turn antennae in the compact helical system (CHS) demonstrated the possibility of ICRF heating in a low-aspect-ratio helical system. Significant heating effects were observed during ICRF heating with two half-turn antennae. During ICRF heating the radiation power also incr eased, and finally the plasma collapsed. Five new antennae were design ed to reduce the release of impurities and were installed for high pow er ICRF heating in the CHS. Four antennae have almost the same design as the previous antennae and are installed in slant ports. The other a ntenna is a new type, of large width (about 24 cm), installed in a ver tically elongated position (U-port). A pre-stub tuner and double twin stub tuners were abopted to the transmitting lines and the matching sy stems to reduce transmitting loss and to facilitate impedance matching . The total absorption power is expected to be more than 1.5 MW.