Investigation of Ion Temperature Characteristics in the HT-7 Tokamak

Characteristics of ion temperature measured with Charge-Exchange Recombination Spectroscopy (CXRS) were studied in Ohmic, Lower-Hybrid-Wave (LHW) driven and Ion-Cyclotron-Resonance-Frequency (ICRF) heated plasmas in HT-7. The results indicate that the central ion temperature T_i0 follows the one-third power law in the product of central line-averaged density`n<sub>e</sub> and plasma current I<sub>p</sub> in Ohmic discharges and is therefore consistent with the Artsimovich scaling law T<sub>i0</sub>= K× (I<sub>p</sub>×B<sub>t</sub>×`n_e ×R²)^1/3. It is shown that there is an appreciable increase of ion temperature during the operation with both LHW and ICRF and that the increment of ion temperature in those shots is mainly due to the energy transfer via collisions between ions and electrons rather that by direct heating of the ions.