An assessment of full wave effects on the propagation and absorption of lower hybrid waves

Abstract

Lower hybrid (LH) waves (ω ci ≪ ω ≪ ω ce, where ω i,e ≡ Zi,eeB/ m i,ec) have the attractive property of damping strongly via electron Landau resonance on relatively fast tail electrons and consequently are well-suited to driving current. Established modeling techniques use Wentzel-Kramers-Brillouin (WKB) expansions with self-consistent non-Maxwellian distributions. Higher order WKB expansions have shown some effects on the parallel wave number evolution and consequently on the damping due to diffraction [G. Pereverzev, Nucl. Fusion 32, 1091 (1991)]. A massively parallel version of the TORIC full wave electromagnetic field solver valid in the LH range of frequencies has been developed [J. C. Wright, Comm. Comp. Phys. 4, 545 (2008)] and coupled to an electron Fokker-Planck solver CQL3D [R. W. Harvey and M. G. McCoy, in Proceedings of the IAEA Technical Committee Meeting, Montreal, 1992 (IAEA Institute of Physics Publishing, Vienna, 1993), USDOC/NTIS Document No. DE93002962, pp. 489-526] in order to self-consistently evolve nonthermal electron distributions characteristic of LH current drive (LHCD) experiments in devices such as Alcator C-Mod and ITER (B0 ≈5 T, n e0≈1× 1020m-3). These simulations represent the first ever self-consistent simulations of LHCD utilizing both a full wave and Fokker-Planck calculation in toroidal geometry. © 2009 American Institute of Physics.