Review of radio frequency conditioning discharges with magnetic fields in superconducting fusion reactors

Wall conditioning techniques based on radio frequency (RF) discharges in fusion devices with permanent magnetic field were developed a few years ago. The first experiments of RF plasma discharges in the ion cyclotron frequency range called ion cyclotron conditioning were performed in Tore Supra and Textor and later also in HT-7 and W7-AS. A high conditioning efficiency in terms of hydrogen removal and surface cleaning has been demonstrated. The other alternative, RF conditioning discharges in the electron cyclotron range of frequencies and called electron cyclotron conditioning, has also been studied in the recent past. Besides surface hydrogen removal and surface cleaning, RF discharges have also been applied to thin film deposition. We report in this paper the main results obtained with several fusion devices on RF conditioning discharges and present conclusions for future devices such as ITER.