ACCELERATION OF ELECTRONS IN THE VICINITY OF A LOWER-HYBRID WAVE-GUIDE ARRAY

The interaction of tokamak plasma edge electrons with the electric nea r field generated by a lower hybrid slow wave antenna is studied. Ante nna field spectra of interest for current drive and/or plasma heating have lobes at high-n(parallel to) values (n(parallel to)>30) intense e nough for resonant acceleration of the relatively cold (similar to 25 eV) edge electrons. For waveguide electric fields, typically around 3 kV/cm, the higher-order modes overlap in the phase-space [B. V. Chirik ov, Phys. Rep. 52, 263 (1979)], so that electron global stochasticity is induced. For Tokamak de Varennes (TdeV) [Decoste et al., Phys. Plas mas 1, 1497 (1994)] conditions and for 90 degrees waveguide phasing, t he stochastic limit in the current drive direction is about 2 keV, det ermined by the last overlapping mode. The progress of electrons throug h accessible phase space is very efficient: the TdeV 32 waveguide arra y can accelerate the electrons to the possible limit. An area-preservi ng map is derived to study the electron dynamics. Surface-of-section p lots fully confirm the resonant wave-particle nature of the interactio n. (C) 1996 American Institute of Physics.