Ion transport in velocity space due to Alfven-ion-cyclotron fluctuations excited in the RF driven tandem mirror plasma

Gentle hump structure on energy spectra of end-loss ions was observed in th e RF driven tandem mirror plasma by use of an end-loss energy component ana lyzer (ELECA), which has been developed in order to directly measure veloci ty distribution functions of the end-loss ions.(1) Ions are heated anisotro pically in the central cell of the tandem mirror by the ICRF wave injection , and Alfven ion-cyclotron (AIC) fluctuations are excited due to the anisot ropic ion temperature.(2) The correlation between the hump structure and th e excitation of the AIC fluctuations was observed experimentally. From the viewpoints of the heating characteristics and the resonance condition, the hump energy was estimated and successfully compared with the experimetal re sults. Influence of the ICRF waves on the hump structure was investigated u sing a bounce averaged Fokker Planck code.(3) The AIC fluctuations enhance the end-loss ions scattered from the trapped region to the loss region, and have direct effects upon the ibn confinement. The energy flux of the enhan ced end-loss ions due to the AIC fluctuations was estimated and the enhance ment factor was obtained. The strong anisotropic ion heating is dangerous f or the ion confinement in the open systems which contain necessarily the lo ss regions.