Self-diffraction effects of electron cyclotron Gaussian beams on noninductively driven current in the International Thermonuclear Experimental Reactor tokamak

The role of diffractive effects not included in standard ray tracing calculations on electron cyclotron current drive (ECCD) is analyzed for an International Thermonuclear Experimental Reactor (ITER) [P. H. Rebut, Fusion Eng. Design 30, 85 (1995)] tokamak configuration, using a quasioptical approach. The power absorbed and the current generated by highly collimated Gaussian beams of electron cyclotron waves (ECW) is calculated using realistic ITER equilibria, relativistic treatment of the wave propagation, and of the driven current, expressed in the formalism of 13 moments transport equations. Effects of beam diffraction on the generated current profile are found to be non-negligible, particularly for off-axis power deposition. (C) 1996 American Institute of Physics.