Influence of nitrogen pre-implantation on deuterium retention in tungsten

Abstract

Abstract:The influence of nitrogen (N) pre-implantation on the deuterium (D) retention in tungsten (W) at different temperatures was investigated. Bulk W samples were exposed to D plasma with a fluence of 110 24 D/m 2 with or without nitrogen pre-implantation at 300 K and 500 K, respectively. Nuclear reaction analysis was applied for the determination of N content and D retention in the near surface. Optical microscopy was used to investigate the surface modification by blistering after implantation. It is shown that, the W:N layers formed during the N preimplantation play very different roles on D retention and blistering in the samples at different temperatures. At 500 K, the W:N layer seems to enhance D diffusion into the bulk by suppressing D loss from the surface, which results in a much higher D concentration in the bulk and larger blisters than without N pre-implantation. At 300 K, the effect of this layer is much less pronounced than that at 500 K.

Effects of nitrogen on hydrogen retention in tungsten: First-principles calculations

“…For example, although the interaction between interstitial hydrogen and nitrogen is very weak, the interstitial nitrogen has a visible effect on the hydrogen diffusion due to its large concentration. experimental results [11][12][13][14][15]. Particularly, as shown in Fig.…”

“…While the above results are encouraging, questions remain as to the influences of nitrogen on hydrogen retention in tungsten [8,9], which are important processes due to their impact on both the safety and operation of fusion reactors [10]. Laboratory experiments have shown increased hydrogen retention in the presence of nitrogen [11][12][13][14][15]. The reasons for this increase are unclear, and while the detailed physics by themselves are of considerable interest, a more pressing matter in estimating nitrogen effects on the hydrogen retention requires information on how hydrogen dissolution and diffusion are influenced by nitrogen.…”

Plasma–wall interactions with nitrogen seeding in all-metal fusion devices: Formation of nitrides and ammonia

“…However, recent experiments on W raise the concern that the presence of a surface nitride layer might increase hydrogen retention by acting as a diffusion barrier for implanted hydrogen isotopes [12,13].…”

Deuterium retention in tungsten exposed to mixed D + N plasma at divertor relevant fluxes in Magnum-PSI

“…Such effects have recently been directly shown to result from an increase in inward diffusion flux by ion driven permeation experiments conducted at low flux [7]. The reason for such an increase is intimately linked with physicochemical changes induced by N implantation at the near surface [7][8][9][10]. An increase in bulk diffusion leads to enhanced retention in W and this may pose problems with respect to tritium inventory in the divertor.…”