Dependence of deuterium retention and surface blistering on deuterium plasma exposure temperature and fluence in lanthanum oxide doped tungsten

Abstract

Oxide dispersion strengthened tungsten (ODS-W) is a potential candidate for plasma-facing materials (PFMs) in future fusion reactors. In this work, deuterium (D) retention and surface blistering in W-1 wt% La2O3 (W-La2O3) have been investigated after exposure to low-energy (40 eV) D plasma with various exposure temperatures (400–600 K) and fluences (3.6 × 1024–1.4 × 1025 D/m2). Surface blistering and D retention exhibit a strong dependence on the exposure temperature and fluence. The most pronounced effect is found at 500 K. The blister-induced defects including dislocations and vacancies are considered to dominate the D retention. At 400 K and 600 K, the D retained in W-La2O3 is governed by unique intrinsic defects including interfaces, micro-pores, and unoxidized La particles. Regarding the exposure fluence, as expected, surface blistering and D retention are positively correlated with it, in which two dominant stages of nucleation and growth for blistering are identified from the changes in area density and size of blisters. Based on the results obtained from W-La2O3, comparisons with W are performed with the exposure condition (500 K, 1.4 × 1025 D/m2) where the blistering and D retention is most pronounced. Although the area density of blisters is similar between the two materials, the average size of blisters is larger in W-La2O3. Notably, an additional high-temperature D desorption shoulder appears in the release spectra of W-La2O3, which is probably due to the particular defects such as interfaces, micro-pores and La particles, and finally resulting in a higher D retention in W-La2O3 than that in W.