Feasibility of arc-discharge and plasma-sputtering methods in cleaning plasma-facing and diagnostics components of fusion reactors

We have studied the feasibility of arc-discharge and plasma-sputtering methods in removing deposited layers from ITER-relevant test samples. Prototype devices have been designed and constructed for the experiments and the cleaning process is monitored by a spectral detection system. The present version of the arc-discharge device is capable of removing 1-µm thick layers from 350-mm2 areas in 4-8 s, but due to the increased roughness of the cleaned surfaces and signs of local melting, mirror-like surfaces cannot be treated by this technique. The plasma-sputtering approach, for its part, is some 5-10 times slower in removing the deposited layers but no changes in surface roughness or morphology of the samples could be observed after the cleaning phase. The arc-discharge technique could therefore be used for rapid cleaning of plasma-facing components during maintenance shutdowns of ITER while in the case of diagnostics mirrors plasma sputtering is preferred.