Lower hybrid current drive in TORE SUPRA and JET

Lower hybrid current drive (LHCD) experiments in TORE SUPRA and JET are reported. Measurements of the scattering matrices of the antennae show good agreement with theory. The current drive efficiency in TORE SUPRA is about 0.2*10²⁰ Am^-2/W with LH power alone and reaches 0.4*10²⁰ Am^-2/W in JET thanks to a high volume-averaged electron temperature (1.9 keV) and also to a synergy between lower hybrid and fast magnetosonic waves. In TORE SUPRA, sawteeth are suppressed and m=1 MHD oscillations the frequency of which clearly depends on the amount of LH power are observed on soft X-rays, and also on nonthermal ECE. In JET ICRH produced sawtooth-free periods are extended by the application of LHCD and current profile broadening has been observed consistent with off-axis fast electron populations. LH power modulation experiments performed in TORE SUPRA show a delayed central electron heating despite the off-axis creation of suprathermal electrons, thus ruling out the possibility of a direct heating through central wave absorption. Successful pellet fuelling of a partially LH driven plasma was obtained in TORE SUPRA.