PSFC/JA-05-18 Current Drive by Electron Bernstein Waves in Spherical Tori

The high-β operating regime of spherical tokamaks (ST), such as in NSTX and MAST, make them attractive fusion devices. For access to such high β regimes, it is necessary to heat and to drive currents in ST plasmas. While such plasmas are overdense to conventional electron cyclotron waves, electron Bernstein waves (EBW) offer an attractive means toward this purpose. The applications of EBWs in STs range from plasma start-up and heating of the ST plasma to modifying and controlling its current profile. The controlling of the current profile could provide better confinement as well as help suppress neoclassical tearing modes. This paper deals with two particular topics. The first topic is on the relevance of relativistic effects in describing the propagation and damping of EBWs. The second topic is on plasma current generation by EBWs.