A critical review of experiments on deuterium retention in displacement-damaged tungsten as function of damaging dose

Abstract

Experimental results from the literature on the evolution of deuterium retention in displacement-damaged tungsten as a function of damaging dose are presented. Except for a few outliers, retention is generally found to increase with the presence of displacement damage. However, total retention results scatter by three orders of magnitude for similar exposure temperatures and are difficult to compare, because they depend on experiment-specific parameters such as the irradiation energy used to produce the displacement damage or the deuterium exposure parameters such as fluence. Even local deuterium concentration measurements were found to scatter by more than one order of magnitude. An experimental methodology is proposed that allows robust conclusions about the evolution of deuterium retention with damage dose and the results are discussed in detail. Recrystallized tungsten is irradiated with 20.3 MeV self-ions at room temperature with different damage doses ranging from 0.001 to 2.3 displacements per atom. The defects are then decorated with a low flux, low-energy deuterium plasma at 450 K sample temperature. 3He Nuclear Reaction Analysis (NRA) shows that the deuterium concentration levels off from the linear increase already at very low damage dose of about 0.005 dpa. At a damage dose of 0.23 dpa a maximum deuterium concentration of about 1.4 at% is reached. Thermal Desorption Spectroscopy (TDS) shows that with damage increasing above 0.005 dpa, the overall shape of the desorption spectra does not change substantially, only their intensities increase. Total amounts derived from TDS are in quantitative agreement with results from 3He-NRA. Experimental results following this methodology also agree quantitatively with very recent parameter-free modeling of damage evolution.