Lower hybrid current drive efficiency on Tore Supra and JET.

The lower hybrid current drive efficiency of 66 Tore Supra pulses has been investigated. The ohmic part of the plasma current (0.6–0.9 MA) is very small (Vloop <50mV) for most of the pulses. Different scaling laws were tested with three input parameters: the wave directivity, the plasma current (Ip) or the volume average temperature (<Te>) and the effective charge (Zeff). When applying these scaling laws to four JET pulses, no discrepancy is found except for the high plasma current (Ip=2.0MA) pulse. Finally the best fit was found by replacing Te (or Ip) by the thermal electron confinement time. This result is supported by the hard X-ray (HXR) diagnostic indicating a fairly good correlation between the plasma edge HXR emission, normalized to the central emission, and the thermal electron confinement time. © 2005 American Institute of Physics [ABSTRACT FROM AUTHOR]