Heating experiments using neutral beams with variable injection angle and ICRF waves in CHS

摘要

Confinement of ripple-trapped energetic ions is studied in a low-aspect-ratio helical system using a neutral beam with variable injection angle. The heating efficiency was found to be very low for the perpendicular injection compared with the tangential one, in the magnetic field configuration which is optimized for the global confinement for the tangential NBI plasmas. Confinement of beam ions was improved by shifting the magnetic axis inward, which was confirmed by the measurement of their energy spectrum. The results are consistent with the calculation of Monte Carlo beam-ion-thermalization code. The poloidal rotation near plasma edge is measured for different injection angles which shows larger value for the perpendicular injection. The fast wave ICRF heating is applied to a low-aspect-ratio helical system. Substantial energy increase is obtained for the NBI target plasma. High energy ion tail is observed in the limited range of pitch angles. (author). (ERA citation 19:002699)