Coupled full-wave and ray-tracing numerical treatment of mode conversion in a tokamak plasma

A new approach for the numerical description of tokamak plasma waves in the ion cyclotron range of frequencies is discussed. It implies coupling of th e full-wave and ray-tracing codes and is capable of unified treatment of wa ves of completely different scale and behavior. The method is applied for s imulations of the electron heating scenario, based on fast wave (FW)-ion Be rnstein wave (IBW) mode conversion near the ion-ion hybrid resonance in Tor e Supra [B. Saoutic , Phys. Rev. Lett. 76, 1647 (1996)]. The two-dimensiona l full-wave "ALCYON" code [D. J. Gambier and A. Samain, Nucl. Fus. 25, 283 (1985)] is used to describe the global FW field pattern in the plasma volum e. A small-scale-waves filter, introduced into the code, artificially damps the mode-converted power, which is further prescribed to IBW rays. Remnant small-scale fields are extracted from the global pattern to provide inform ation necessary for IBW rays to start. Three-dimensional evolution of IBW r ays is simulated by the "RAYS" ray-tracing code [Yu. Petrov, Nucl. Fus. 34, 63 (1994)], being unrestricted by finite mesh size and finite Larmor radiu s effects. (C) 2000 American Institute of Physics. [S1070-664X(00)00203-2].