Ion heating by lower hybrid wave in the HT-7 tokamak

Lower hybrid wave (LHW) heating has been investigated in the HT-7 supercond ucting tokamak. It has been observed that the plasma performance is obvious ly enhanced by LHW heating. The ion temperature was increased by 0.4 keV an d the electron temperature by 0.3 keV. Meanwhile the central line-averaged electron density was increased from 1 x 10(19) to 2.6 x 10(19) m(-3). The h igh-energy ion tail produced by the LHW was observed from the charge-exchan ge spectra measured by neutral particle analysis. An ion heating efficiency of (2-3) x 10(13) eV kW(-1) cm(-3) was obtained in the experiments. The ev olution of the profiles of ion temperature shows clearly an off-axis ion he ating by LHW, which is in agreement with code simulations.