ICRF system efficiency

•Discussing the overall efficiency of an ICRF system. The efficiency of heating and current drive systems is one of the key parameters for a successful operation of fusion demonstration power plants like DEMO. In an earlier review article, overall plug efficiencies of H & CD systems were estimated at 20 – 30 % Bradley et al.. We present here a detailed breakdown based where possible on experimental data for the overall efficiency (plug to power in plasma) of ICRF (ion cyclotron range of frequencies) systems: 1) the technical efficiencies (RF generator, transmission lines, losses in antenna); 2) the interface efficiency (hardware/ plasma) and 3) heating efficiency (absorption in plasma). This leads currently to an overall efficiency for heating in the range 40% to 55%. Future improvements can lead to an overall efficiency of up to 69 %. In a second step we address the current drive efficiency (in terms of kA/MW absorbed).