On maximizing the ICRF antenna loading for ITER plasmas

Mayoral, M.-L.*; Bobkov, V.*; Colas, L.*; Goniche, M.*; Hosea, J.*; Kwak, J. G.*; Pinsker, R.*; Moriyama, Shinichi; Wukitch, S.*; Baity, F. W.*; Carpentier-Chouchana, S.*; Czarnecka, A.*; Ekedahl, A.*; Hanson, G.*; Jacquet, P.*; Lamalle, P.*; Monakhov, I.*; Murakami, Masanori*; Nagy, A.*; Nightingale, M.*; Noterdaeme, J.-M.*; Ongena, J.*; Ryan, P. M.*; Vrancken, M.*; Wilson, J. R.*; EFDA-JET Contributors* for the Pedestal and Edge Physics and the Steady State Operation Topical Grou*; ASDEX Upgrade Team*; ITPA "Integrated Operation Scenarios" Group*

For any given ICRF antenna design for ITER, the maximum achievable power strongly depends on the density profiles in the SOL. It has been suggested that gas injection can be used to modify the SOL profiles and thus minimize the sensitivity of the ICRF coupling to variations in the density at the edge of the confined plasma. Recently joint experiments coordinated by the ITPA were performed to characterize further this method. An increase in SOL density during gas injection led to improved coupling for all tokamaks in this multi-machine comparison. The effectiveness of using gas injection over a wide range of conditions, as a tool to tailor the edge density in front of the ICRF antennas, is documented for different gas inlet location and plasma configurations. In addition, any deleterious effects on the confinement and interaction with the antenna near-field are not investigated.