First wall upgrade for the reversed field pinch RFX

The inner surface of the RFX vacuum vessel is protected by a first wall made up by 2016 polycrystalline graphite tiles. Due to the dimensions of the largest ports, inspection, maintenance and replacement of the first wall components can be carried out only by a remote handling system. Inspections performed during the first four years of operation showed evidence of some plasma surface interaction not only on the graphite tiles, but also on small portions of the vacuum vessel in the interspace between two tiles. Erosion phenomena were observed in the area which corresponds to the insulated poloidal gaps of the stabilizing shell that surrounds the vacuum vessel. New graphite tiles to be installed in these regions were designed, with a shape which completely closes the interspace in the poloidal direction between the tiles. During the last shut down, in 1995, all the 112 tiles were successfully replaced by means of the remote handling system.