ICRF physics aspects of wall conditioning with conventional antennas in large-size tokamaks

This paper focuses on a study of the principal operation aspects of standard ICRF heating antennas in the ion cyclotron wall conditioning (ICWC) mode: (i) ability of the antenna to ignite the cleaning discharge safely and reliably in different gases including those most likely to be used in ITER – He, H 2 , D 2 and their mixtures, (ii) the antenna capacity to couple a large fraction of the RF generator power (>50%) to low density (∼10 16 –10 18 m −3 ) plasmas and (iii) the RF power absorption schemes aimed at improved RF plasma homogeneity and enhanced conditioning effect. The ICWC discharge optimization in terms of RF plasma wave excitation/absorption resulted in successful simulation of the conditioning scenarios for ITER operation at full field (JET) and half-field (TEXTOR, TORE SUPRA, ASDEX Upgrade).