Fast- and slow-wave heating of ion cyclotron range of frequencies in the Large Helical Device

Wave-heating at the fundamental ion-cyclotron frequency was applied to a hydrogen plasma in the Large Helical Device (LHD) over a range of plasma densities from 0.2-8x1019 m-3. Substantial heating was observed for all densities. In the low-density plasma (less than 0.4x1019 m-3) ion-cyclotron-wave (shear Alfven wave) heating was effective. For high-density plasmas, a fast-wave should be excited, and in this case also, effective heating was observed with the presence of the NBI beam component. The wave damping mechanism may be attributed to the finite gyro-radius effect on beam ions by the right-handed polarized wave. The experimental results were compared with an analysis using the full-wave code. The heating performance was a little worse than that of the usual two-ion hybrid-heating mode. (author)