Effect of the electron temperature on LHCD efficiency in the HL-1 tokamak

A simple model is presented for calculating the lower hybrid wave (LHW) power deposit along the ray tracing and for obtaining the RF current profiles. Computations show that much of the LHW power is absorbed by electron-ion collision near plasma edge when the central electron temperature is less than 1 keV, and therefore the current drive efficiency is low. Under this condition, the LHCD efficiency increases in principle with increasing electron temperature. The calculated results are in agreement with that of the HL-1 tokamak lower hybrid current drive (LHCD) experiments, hence interpreting why the LHCD efficiency is lower in a large or middle sized tokamak than in a small one