Radial Transport of High-Energy Ions Caused by Low-Frequency Fluctuations in the GAMMA 10 Tandem Mirror

Abstract

Plasmas with high ion-temperature of several keV have been produced by using ion-cyclotron range of frequency (ICRF) heating in the GAMMA 10 tandem mirror. In such high performance plasmas, high and low-frequency fluctuations are excited and ions trapped in the magnetic field interact with such fluctuations. Three types of wave-particle interactions have been observed in the GAMMA 10 tandem mirror. The turning point diffusion near the ion cyclotron resonance layer has been observed in minimum-B configuration on the anchor cell. Pitch angle scattering of high-energy ions due to the AIC modes and low-frequency waves which have differential frequencies between discrete peaks of the AIC modes are clearly detected. The drift-type fluctuations are clearly observed in the central cell. By using a semiconductor detector, high-energy ions are detected at the radial location far from the plasma edge. The fluctuation, of which frequency is the same as that of drift-type fluctuation, is observed in the signal of high-energy ions. From the pitch angle distribution of the phase differences between both fluctuations, radial transport of high-energy ions caused by drift-type fluctuations near their turning points in the confining mirror field is suggested in the experiments.