High power ion cyclotron range of frequency heating in a compact helical system

The ion cyclotron range of frequency (ICRF) heating experiment with two 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 increased, and finally the plasma collapsed. Five new antennae were designed to reduce the release of impurities and were installed for high power ICRF heating in the CHS. Four antennae have almost the same design as the previous antennae and are installed in slant ports. The other antenna is a new type, of large width (about 24 cm), installed in a vertically elongated position (U-port). A pre-stub tuner and double twin stub tuners were adopted to the transmitting lines and the matching systems to reduce transmitting loss and to facilitate impedance matching. The total absorption power is expected to be more than 1.5 MW.