Plasma cleaning technique for the removal of mixed materials

Erosion of materials by physical sputtering is the most fundamental of plasma–surface interactions in tokamaks. Carbon and tungsten materials planned to be used in ITER divertor are subjected to erosion, which produces local redeposition of mixed layers. Tritium retention in mixed materials is the major concern due to the limits imposed for safety reason by nuclear licensing. No technique has yet been proven capable of remove trapped tritium in ITER operating environment. In-situ oxidative cleaning techniques have been developed to remove co-deposits. Since oxygen can be incompatible with Be first wall (getter effect), a plasma cleaning using hydrogen–argon gas mixture has been proposed in this work. C–W mixed materials were produced for this purpose by capacitively coupled RF plasma sputtering. The process has been investigated by optical emission spectroscopy and Langmuir probe.