Tritium distribution on plasma-facing tiles from ASDEX Upgrade

Tritium surface distribution on the plasma-facing tiles used in the divertor region and the central column of ASDEX Upgrade was measured by Tritium Imaging Plate Technique. The tritium intensity is high at the dome baffle underneath the X point, the outer divertor region and the mid-plane or lower side of the central column. In contrast, little tritium was retained in the carbon deposition found in the inner strike point module tiles. Such profile is very similar to that observed in JT-60U, indicating that long-term tritium retention in ASDEX Upgrade was dominated by the implantation of energetic tritons escaping from the main plasma without losing their initial energy (1 MeV) rather than the codeposition of eroded carbon and hydrogen isotopes. However, such tritium profile was modified by carbon deposition and thermal load, particularly on the divertor target tiles and the central column.