Faraday shield dissipation in the drivers of SPIDER based on electromagnetic 3D calculations

SPIDER (Source for the Production of Ions of Deuterium Extracted from Rf plasma) is a full-scale prototype of the ITER NBI source. It is based on the concept of inductive coupling between radio-frequency current drive and plasma. Present three-dimensional (3D) electromagnetic calculations of stationary RF fields in SPIDER permit an evaluation of the power dissipation in its main constituents. Taking experimental plasma parameters as input, we concentrate on the power dissipation in the copper-made Faraday shield lateral wall (FSLW) of the source for discharges with and without a static magnetic filter field. In agreement with our previous results and a first comparison with calorimetry data from the FSLW cooling circuit, the FSLW cylinder alone absorbs around 50% of the available power for the studied plasma parameters. A hypothesized improvement of transport confinement may increase significantly the efficiency. • 3D electromagnetic calculations of radio-frequency inductive coupling in the geometry of SPIDER device. • Spatially resolved distribution of ohmic power density in Faraday-shield cylindrical wall. • Obtained efficiency (generator power/absorbed power) of the RF plasma source in real plasma scenarios. • Around half the generator power is lost in the cylindrical wall of the Faraday-shield according to calculations and experiments.