RF experiments on PLT

A variety of rf experiments are being conducted on PLT in order to explore rf techniques which could improve tokamak performance parameters. Of special importance are the studies of ion Bernstein wave (IBW) heating, lower hybrid MHD stabilization and electron heating, down-shifted electron cyclotron heating, and fast wave current drive. Ion Bernstein wave heating results at modest power indicate that the particle confinement time could be enhanced relative to that for fast wave heating in the ion cyclotron range of frequencies (ICRF) and neutral beam heating. At these power levels a conclusive determination of energy confinement scaling with power cannot yet be given. Central sawtooth and m=l MHD stabilization is being obtained With centrally peaked lower hybrid (LH) current drive and the central electron temperature is peaking to values (-5 kev) well outside the bounds of "profile consistency". In this case the electron energy confinement is apparently increased relative to the ohmic value. The production of relativistic electrons via heating at the down-shifted electron cyclotron (EC) frequency is found to be consistent with theoretical predictions and lends support to the use of this method for heating in relatively high magnetic field devices. Finally, the study of fast wave current drive will begin in the near future to determine the efficacy of this method relative to that for the slow wave case and to determine if high density operation is feasible.