Lower hybrid current drive at high density on Tore Supra

Lower hybrid current drive (LHCD) experiments with line-averaged density varying between 1.5 × 1019 and 6 × 1019 m−3 are performed on the Tore Supra tokamak under quasi-steady-state conditions with respect to the fast electron dynamics. The LHCD efficiency is analysed from the fast electron bremsstrahlung (FEB) and electron cyclotron emission (ECE). The effect of plasma equilibrium and particle fuelling is documented. It is concluded that the fast decay of FEB with plasma density could be consistent with simple scaling of the current drive efficiency and FEB. Plasma edge measurements are presented looking for the effect on fast electron emission. In a specific case of particle fuelling, an anomalous decay of the hard x-ray and ECE signals suggests deleterious interaction of the wave with edge plasma.