Parasitic coupling of ion Bernstein waves with ICRF fast wave excitation in tokamaks

Abstract

Summary form only given, as follows. Analysis and computer simulation is presented for investigating the coupling of ion cyclotron range of frequency (ICRF) waves to tokamak plasmas using phased coil antenna arrays. The model accounts for three-dimensional antenna, and feeder current effects, an idealized Faraday shield, an antenna cavity which is finite in all three dimensions and warm plasma effects. The WIGS computer code, developed by the authors, is used to calculate the antenna radiation resistance and the spectrum of the ICRF power coupled to the plasma. Parasitic coupling to the ion Bernstein wave during fast wave heating experiments is investigated. Parasitic coupling to the ion Bernstein wave in the edge plasma region is shown to be important for low parallel wavenumbers during minority ion heating with large gradients in the plasma density near the edge of the plasma. The sensitivity of the parasitic coupling to changes in the cavity dimensions, current feeder configuration, coil current phase velocity and edge plasma profiles is discussed. The fraction of the launched power coupled to the ion Bernstein wave is to vary substantially with the antenna and plasma parameters and the phase difference between the excitation of adjacent antenna coils. Specific results are shown for the antenna and plasma parameters of the TFTR and JET tokamaks.