Studies on retention of tritium implanted into tungsten by β-ray-induced X-ray spectrometry

Trapping and diffusion of tritium implanted into tungsten at room temperature were examined by β-ray-induced X-ray spectrometry. One of two thin tungsten plates used was previously irradiated with He ions. After the tritium irradiation, X-ray spectra from a W sample were measured in an argon atmosphere, and changes in the X-ray spectra with time were followed for five months at room temperature. The observed X-ray spectra consisted of three characteristic X-ray peaks and a bremsstrahlung X-ray peak. For the W sample without He pre-irradiation all characteristic X-ray intensities decreased with time, while those for the sample with He pre-irradiation were almost constant, indicating that the He irradiation strongly affects the migration of tritium. Furthermore, the X-ray spectra were analyzed by computer simulation to estimate a tritium depth profile. From those results, the diffusion coefficient of tritium at room temperature and effects of He pre-irradiation on trapping of tritium were evaluated.