Plasma-Wall-Interaction Diagnostics in ITER: Dust, Erosion, and Tritium Retention

Plasma-wall interaction in fusion devices is unavoidable and leads to material erosion, dust formation, and tritium retention. Erosion of plasma-facing material and generation of dust inside ITER can significantly affect the operation. This is because the total in-vessel dust and tritium inventories during an operational campaign are required to be below limits of 1000 and 1 kg, respectively, imposed by safety considerations. To ensure respect of these limits, dust and tritium inventories should be monitored during the operational campaign of ITER. The level of erosion will be monitored by laser ranging techniques. To manage the dust inventory, local dust monitors from a number of locations will measure local dust concentration and accumulation. An additional important issue is dust lying on hot surfaces. In terms of safety, "hot dust" inventory is also strictly limited. Several techniques have been proposed to monitor the hot dust amount. Finally, the in-vessel tritium inventory must be limited and monitored. Assessment of the deficit in the tritium fuel supply is a way of measuring in-vessel tritium retention; however, this will have to be complemented by local surface analysis. Several diagnostic methods are introduced and compared with each other in order to find the most promising ITER-relevant concepts.