The influence of neon or argon impurities on deuterium permeation in tungsten

Nitrogen (N) or neon (Ne) in the divertor and argon (Ar) puffing in the first wall have been proposed to reduce the local power loads on tungsten (W) plasma facing components. The impurities sputter and modify the W surface, which can affect hydrogen (H, D, T) transport in W. In this study, mixed D + Ne or D + Ar ion driven permeation experiments were performed to investigate the influence of Ne or Ar impurities on D transport. The D permeation flux for mixed irradiation was lower in comparison to D-only irradiation at T> 500 K, opposite to trends observed for N. The reason for the observed decrease in permeation flux was interpreted to arise from combined effects of sputtering and possible precipitation. The lag times for D + Ne case was slower than D-only case, while D + Ar was faster. This indicates Ne precipitation effects may influence the H transport in W similar to helium. (C) 2014 Elsevier B.V. All rights reserved.