Microscopically Nonuniform Deposition and Deuterium Retention in the Divertor in JET with ITER-Like Wall

The divertor surfaces in JET with ITER-like wall (ILW) have been studied using micro ion beam analysis (µ-IBA) methods and scanning electron microscopy (SEM). Deposited layers with beryllium as main constituent had been formed during plasma operations through 2011- 2012. The deuterium trapping and impurity deposition were non-uniform, frequently enhanced within regions reaching in size from 10µm to 200µm. Enhanced amounts of D and impurities were found at pits, cracks and valleys in the tungsten coating. The impurity deposition and fuel retention were correlated with the surface slope with respect to the direction of ion incidence. Typically more than 70% of the total measured areal density of trapped D was found in less than 30% of the surface area. This of consequence for the interpretation of other surface analyses and in extrapolation from fuel retention in JET with ITER-like wall and rough divertor surfaces to ITER with smoother surfaces.
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EFDC140111 938.49 Kb