Deuterium recombination coefficient on tungsten surface determined by plasma driven permeation

Abstract

Deuterium (D) plasma driven permeation (PDP) experiments for tungsten (W) samples were conducted by a linear radio frequency (RF) plasma device. In the PDP experiment, the W sample surface is perpendicular to the grain elongation direction. The D ion flux is in the order of 1021 m−2 s−1 determined by a double Langmuir probe. The results show that bias had a limited effect on the D plasma driven permeation behavior. The D recombination coefficient on W surface is obtained at the temperature ranging from 740 K to 1031 K. The experimentally measured recombination coefficient for a pristine W surface is lower than that for a clean W surface. The effect of recombination coefficient on the D permeation and retention behaviors in W are studied by Hydrogen Isotope Diffusion and Trapping (HIDT) simulation code. The low recombination coefficient leads to a high D concentration in W and a high permeation rate at the back surface. The D permeation rate through a 8 mm thick W with a pristine surface is estimated to be 8.1 × 1018 D m s−1 under the incident ion flux of 1 × 1024 m−2 s−1 and temperature of 1173 K.