Studies of spatial uniformity of glow discharge cleaning plasmas on the RFX-mod device

In RFX-mod different types of Glow Discharge Cleaning (GDC) plasmas are used as wall treatment procedures. An extensive set of diagnostics allowed a characterization of these cold and weakly ionized plasmas in the different operative conditions that are available. A strong toroidal non-uniformity of ion current at the edge, that gives the measure of the effectiveness of the physical sputtering, was measured by different diagnostics. The non-uniformity was mitigated by decreasing the gas pressure but it could not be avoided.