Development of ICRF wall conditioning technique on divertor-type tokamaks ASDEX Upgrade and JET

Encouraging results of efficient wall conditioning with ICRF discharges achieved on the circular tokamaks (without divertors) TEXTOR, TORE SUPRA, HT-7 stimulated the next step in the development of an alternative wall conditioning technique that is relevant to reactor-scale superconducting fusion machines. Here, the first results on the ICRF discharge initiation and the wall conditioning on the large-size non-circular tokamaks ASDEX Upgrade and JET using the standard ICRF antennas are reported. Analysis of the mass-spectrum data on both machines indicates noticeable outgassing of deuterium, water and hydrocarbons from the walls despite operating with a non-optimized set of ICRF discharge parameters.