Lower hybrid current drive data obtained on the JT-60 tokamak at a density of e ≌ 1 × 1019 m−3 are analysed. The parallel and perpendicular pressures of the superthermal electron tail are deduced from magnetic measurements. The energy stored in the superthermal electrons is found to be comparable to the bulk stored energy, and a significant pressure anisotropy of βp||/βp⊥ ≌ 3 is inferred. The electron tail distribution function can be modelled by a three-temperature Maxwellian with a flat tail extending to the accessibility energy in the forward direction, a perpendicular temperature of 150 keV, a backward parallel temperature of 250 keV, and a backward to forward ratio of 2. These results are consistent with expectations based on theory, the results of a detailed numerical modelling, and the model distribution functions inferred previously on smaller tokamaks.
Upper hybrid emission from a magnetized gas discharge plasma