Studies of high energy ions in Heliotron J

In order to investigate the effect of the magnetic field components on the energetic particle confinement in helical-axis heliotron configuration, the NBI and ICRF heating experiments have been carried out in Heliotron J with changing the mirror ripple component of the magnetic field. By scanning the charge exchange (CX) neutral particle analyzer (NPA) in the toroidal direction, it is found that the CX flux in NBI plasmas decreases with increasing the mirror ripple component when the toroidal angle of CX-NPA set perpendicularly, which can be interpreted by the change in the loss cone shape predicted by a theoretical calculation. The 1/e decay time of the CX flux for the tangentially injected beam ions, on the other hand, increases with the mirror ripple. In the ICRF minority heating experiment, it is found that the tail temperature of the minority ion increases with the ICRF power. The high energy minority ion up to 8 keV is observed only in the higher mirror ripple configurations. These results suggest that the configuration with higher mirror ripple is favorable for the confinement of the energetic particles whose pitch angles are parallel direction in this experimental condition. (author)