Hydrogenic retention in tungsten exposed to ITER divertor relevant plasma flux densities

Tungsten targets are exposed to the plasma conditions expected at the strike point of a detached ITER divertor (similar to 10(24) D/m(2)s, Te similar to 2 eV). The surface temperature of the target is similar to 1600 K at the center and decreased radially to similar to 1000 K at the edges. A 2-D spatial scan of the W target using nuclear reaction analysis (NRA) shows an asymmetric D retention profile with the lowest retention values at the center of the target and the highest 6 mm off-center. Even in the regions of larger retention, the D concentrations were <= 5 x 10(15) D/cm(2) as measured by NRA. Thermal desorption spectroscopy (TDS) is used to measure the global D retention. Very low retention with retained fractions ranging from 10(-7) to 10(-5) D-retained/D-incident were measured with TDS. Both NRA and TDS results show no clear dependence of retention on incident fluence possibly indicating the absence of plasma-driven trap production in W under these conditions. (C) 2009 Elsevier B.V. All rights reserved

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