Fuel retention, a crucial issue for next step devices, is assessed in present tokamaks using two methods : particle balance performed during shots and post mortem analysis carried out during shutdowns between experimental campaigns. Post mortem analysis generally gives lower estimates of fuel retention than particle balance. In order to understand the discrepancy between these two methods, a dedicated experimental campaign has been performed in Tore Supra to load the vessel walls with deuterium (D) and monitor the trapped D inventory through particle balance. The campaign was followed by an extensive post mortem analysis phase. This paper presents the status of the analysis phase, in particular the assessment of the D content in gap deposits. Indeed, using combined surface analysis techniques, it was possible to derive the relative contributions of different zones of interest on the Tore Supra limiter (erosion, thick deposits, thin deposits), showing that the post mortem inventory is mainly due to codeposition (90% of the total), in particular due to gap deposits. At the present stage of analysis, 50% of the inventory deduced from particle balance has been found through post mortem analysis, a significant progress with respect to previous studies (factor 8-10 discrepancy).

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A dedicated study on fuel retention has been launched in Tore Supra which included a D wallloading campaign and the dismantling of the main limiter (Deuterium Inventory in Tore Supra, DITS project). This paper presents new results of post mortem analyses performed on selected limiter tiles. Scanning electron microscopy shows thick layers with poloidally oriented tip-shaped structures in deposition zones. In the erosion zone deposits inside the open porosities of the bulk material of the tiles were found. Raman microscopy indicates that hard deuterated amorphous carbon layers are deposited on the limiter tiles and on their gap sides. Secondary ion mass spectrometry D depth profiles show an increase of the D content near the bottom of the gap, in agreement with previous results. The campaign markers ( 13 C and 11 B) are found in only 2 out of 7 measurements in the deposited layers. Finally, the agreement of the SIMS data with previous NRA measurements is discussed, especially discrepancies possibly due to the non-uniformity of the samples.

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