Fusion Science and Technology / Volume 48 / Number 1 / July/August 2005 / Pages 573-576
Technical Paper / Tritium Science and Technology - Materials Interaction and Permeation
Tritium surface distributions on the plasma-facing surface and four sides of JET Mk IIA divertor tiles employed in the D-T operation phase of JET were measured by Tritium Imaging Plate Technique (TIPT). Tritium distribution on the plasma-facing surface was consistent with carbon deposition profiles and asymmetric in both poloidal and toroidal directions. The toroidal asymmetry was attributed to the alignment of the tiles preventing direct impact of flux lines to tile edges. Accordingly, no significant carbon deposition or tritium accumulation was observed on two sides facing the toroidal direction. As already reported, heavy codeposition retaining high levels of tritium was observed on the plasma-shadow area of the horizontal target tile surface and the bottom side of the vertical target tile of the inner divertor region where it was kept relatively cool by water coolant. In addition, TIPT has clearly distinguished at least two different carbon deposition layers with different tritium retention in poloidal direction, showing that the poloidal asymmetry on the horizontal target tiles is due to the different carbon deposition properties in the poloidal direction. All the results suggest that tritium retention in the divertor area, which was determined by the carbon/hydrocarbon distribution, correlates closely with divertor geometry and surface temperature.