Spatially Dependent Rate Theory Modeling of Thermal Desorption Spectrometry of Helium-Implanted Iron

Helium effects are among the most critical subjects in fusion materials research. A major task in the study of He effects is to understand how He interacts with irradiation-induced and/or inherent defects and how the interactions govern the subsequent microstructural evolution. Thermal desorption spectrometry (TDS) provides an appropriate platform for both experimentally probing the kinetics and energetics of He-defect interactions and computationally validating the parameterization of rate theory models. In this paper we present preliminary results on the spatially dependent rate theory modeling of TDS of He-implanted single crystalline iron under the same conditions as explored in our recent experiments. Included in the present model are previously reported migration energies for self-interstitial-atom (SIA), di-SIA and interstitial He from ab initio calculations, and binding energies of He_xV_y, V_m and I_n clusters from thermodynamic calculations or ab initio based extrapolations. With a small amount of parameter optimization, several major features observed in the experimental TDS spectra have been reasonably reproduced by the model, while further and more complete validation through both experiments and computation remains to be carried out.