Transport of intense LH pulses into a tokamak plasma

Application of lower-hybrid (LH) power in short, intense pulses in the 5-10 GW range should overcome the limiting effects of Landau damping, and there by permit the penetration of LH power into the interior of large-scale plas mas. We show that, under such very intense LH pulses, wave coupling may det eriorate because of nonlinear density changes due to the ponderomotive forc e Effects in front of the grill. Ponderomotive for ces are also likely to i nduce strong plasma bias and consequent poloidal and toroidal plasma rotati on. Although backward electric currents, created in the plasma by intense L H pulses, dissipate a large portion of the radio frequency power absorbed: the current drive efficiency is acceptable. We use a numerical simulation o f wave-particle interactions to analyse the applicability of standard quasi linear theory to the case of large energy flux densities. The initial resul ts indicate the existence of important restrictions on the use of the quasi linear approximation. The results of the present paper also indicate that s ome of the effects considerably alter some ideas of Cohen et al.