The influence of displacement damage on deuterium retention in tungsten exposed to divertor plasma in DIII-D

Experiments were conducted to determine the influence of displacement damage on retention of deuterium in tungsten plasma-facing components in a tokamak. Tungsten samples, previously damaged by ion irradiation, were exposed to the outer strike point of attached H-mode plasmas in DIII-D. Nuclear reaction analysis (NRA) was used to measure the depth profile of deuterium retained in the tungsten. Displacement damage increased the concentration of retained deuterium to the maximum depth (about 2.5 (micro)m) of the damage, to concentrations up to 0.003 D/W, compared to D/W < 10-5 in undamaged W. Tungsten coverage on adjacent carbon surfaces of the probe was mapped by Rutherford backscattering, giving the average tungsten erosion rate and spatial variation of redeposition.