Three-dimensional calculations of the inductive coupling between radio-frequency waves and plasma in the drivers of the SPIDER device

Abstract: This work documents the initial 3D calculations to simulate the coupling between radio-frequency (RF) waves and plasma in discharges of the SPIDER device. Axisymmetric 3D calculations in the plasma domain alone compare well against equivalent 2D cases. A model of SPIDER driver, the cylindrical chamber where the plasma is heated by the RF drive, is then defined including the metallic parts of the Faraday shield, insulator and vacuum layer up to the RF winding (not included in the calculation domain). Estimates of the power share in the different parts are obtained using experimental conditions and plasma data. The results are sensitive to the particular geometry of the driver and the temperature of the Faraday shield, but generally agree with the experimental knowledge. The ratio between total delivered power and plasma absorbed power is found, depending on the plasma parameters, in the range 30--45\%