A study of the influence of prolonged baking on deuterium depth distribution and release in JET ILW components

Abstract Samples of JET ILW divertor and limiter tiles extracted from JET after the third ILW campaign underwent baking at elevated temperatures (350°C and 240°C, respectively) for 60-140 hours, to simulate the effects of baking as previously planned for ITER divertor and first wall. A combination of thermal desorption spectroscopy (TDS) and ion beam analysis (IBA) was used to characterize the dynamics of deuterium outgassing during baking and the resulting changes in deuterium depth distribution. It is shown that deuterium release during baking follow a power law time dependence with the average power law exponent of ~0.85 for divertor samples and ~0.68 for limiter ones. For divertor samples the average total fuel removal efficiency is ~47.5% and the near-surface one is ~21%, while for limiter samples they are ~3.8% and 97%, respectively. Spatial redistribution of deuterium during prolonged baking is demonstrated. The combination of TDS and IBA reveal a fundamental difference in deuterium redistribution behaviour between divertor and limiter baking conditions, with predominant diffusion towards the surface followed by desorption in the former and predominant inward diffusion in the latter. Possible promotion of fuel outgassing by a loose morphology of thick co-deposit layers is also observed.