Electron cyclotron heating combined with lower hybrid current drive on WT-3

Lower hybrid current drive (LHCD) is applied to improve the confinement in the WT-3 tokamak. With increasing the lower hybrid (LH) power, a sharp decrease in electron thermal diffusivity χe is observed at a certain LF power. The χe is directly measured by applying the simple time-to-peak method to propagation of a heat pulse induced by a short electron cyclotron heating (ECH) pulse. A high electron temperature is obtained by applying ECH to the LHCD plasma with improved χe. The efficiency of ECH in the LHCD plasma with improved χe becomes three times that in ohmic heating plasmas.