E. Gauthier

Deuterium inventory in Tore Supra: reconciling particle balance and post-mortem analysis

Fuel retention, a crucial issue for next step devices, is assessed in present-day 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 integrated 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 of the Tore Supra limiter. This paper presents the status of the analysis phase, including the assessment of the D content in the castellated tile structure of the limiter. Indeed, using combined surface analysis techniques, it was possible to derive the relative contributions of different zones of interest on the 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. However, deuterium was also evidenced deep into the material in erosion zones (10% of the total). At the present stage of the 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). This shows that post-mortem analysis can be consistent with particle balance provided specific procedures are implemented (dedicated campaign followed by extensive post-mortem analysis). Both techniques are needed for a reliable assessment of fuel retention in tokamaks, giving complementary information on how much and where fuel is retained in the vessel walls.

Application of ICRF waves in tokamaks beyond heating

Note: 30th EPS Conference on Controlled Fusion and Plasma Physics, St Petersbourg, Russia, July 2003 (invited talk) Reference CRPP-CONF-2003-042 Record created on 2008-05-13, modified on 2016-08-08

Deuterium Inventory in Tore Supra: status of post-mortem analyses

A dedicated study on fuel retention has been launched in Tore Supra which included a D wall-loading 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 (13C and 11B) are found in only 2 out of 7 measurements in the deposited layers. Finally, the agreement of the SIMS data with previous nuclear reaction analysis (NRA) measurements is discussed, especially discrepancies possibly due to the non-uniformity of the samples.

Innovative diagnostics for ITER physics addressed in JET

In recent years, JET diagnostic capability has been significantly improved to widen the range of physical phenomena that can be studied and thus contribute to the understanding of some ITER relevant issues. The most significant results reported in this paper refer to the plasma wall interactions, the interplay between core and edge physics and fast particles. A synergy between new infrared cameras, visible cameras and spectroscopy diagnostics has allowed investigating a series of new aspects of the plasma wall interactions. The power loads on the plasma facing components of JET main chambers have been assessed at steady state and during transient events like ELMs and disruptions. Evidence of filaments in the edge region of the plasma has been collected with a new fast visible camera and high resolution Thomson scattering. The physics of detached plasmas and some new aspects of dust formation have also been devoted particular attention. The influence of the edge plasma on the core has been investigated with upgraded active spectroscopy, providing new information on momentum transport and the effects of impurity injection on ELMs and ITBs and their interdependence. Given the fact that JET is the only machine with a plasma volume big enough to confine the alphas, a coherent programme of diagnostic developments for the energetic particles has been undertaken. With upgraded γ-ray spectroscopy and a new scintillator probe, it is now possible to study both the redistribution and the losses of the fast particles in various plasma conditions.