Effect of energetic ion loss on ICRF heating efficiency and energy confinement time in heliotrons

The ICRF heating efficiency and the global energy confinement time during I CRF heating are investigated, including the effect of energetic ion loss in heliotrons. The approximate formula of ICRF heating efficiency is derived using results based on Monte Carlo simulations (Murakami, S., et al., Fusio n Eng. Des. 26 (1995) 209). The global energy confinement time including th e energetic ion effect can be expressed in heliotrons in terms of ICRF heat ing power, plasma density and magnetic field strength. Results in plasmas a t CHS show a systematic decrease of the global energy confinement time due to energetic ion loss from the assumed energy confinement scaling law, whic h is consistent with the experimental observations. The model is also appli ed to ICRF minority heating in LHD plasmas in two cases of typical magnetic configurations. A clear increase of the global energy confinement time due to the stored energy of energetic tail ions is obtained in the 'orbit impr oved' configuration, while a decrease is observed in the 'standard' configu ration.