ICRF/edge interaction guidelines for ICRF antenna design and initial ICRF/edge interaction experiments on the tore supra tokamak

Understanding ion cyclotron range of frequency (ICRF) antenna interaction with the edge/scrape-off-layer (SOL) plasma is crucial to building antennas that can survive long-pulse or steady-state high-power operation in plasmas. The global effects of ICRF/edge interactions are discussed. The present knowledge of ICRF-induced sheath interactions with the edge and SOL plasmas in magnetic fusion experiments is quantitatively reviewed and added to. The design principles and equations governing plasma heat loading and the sputtering of Faraday shields and the bumper limiters of ICRF antennas for long-pulse and steady-state devices are presented. Electrostatic sheaths on Faraday shields and bumper limiters are discussed, and an analytic estimate of the induced direct-current (dc) plasma potential at the lateral protection (bumper limiters) of ICRF antennas is given. This is a new result. This estimated dc voltage is used to give the total power flow to the lateral protection, and an expression for the power flux is given-also with new results. Equations to use in estimating impurity production (sputtering) and principles for minimizing impurity production are reviewed. Similar equations and estimates for electromotive radio-frequency sheaths are given, and new scaling laws for the dc voltage and power flow to the ICRF antenna lateral protection due to electromotive sheaths are proposed. The initial results from the ICRF/edge interaction experiments on Tore Supra are presented and discussed in light of the theoretical and heuristic results given.