In situ observation of tritium interactions with Pd and Zr by β-ray induced X-ray spectrometry

A newly developed technique, β-ray induced X-ray spectrometry (BIXS), was applied to in situ and real-time measurements of depth profiles of tritium in palladium and zirconium. Two distinct spectra were detected by BIXS, one due to the characteristic X-rays giving rise to a sharp intense peak; and the other due to the bremsstrahlung X-rays leading to a broad weak peak. The intensities of these peaks for palladium decreased with time at room temperature, while they were almost constant for the Zr-sample at room temperature. Heating the Zr-sample, however, caused similar changes in the spectra as those for palladium at room temperature. It was found that these phenomena are due to the diffusion of tritium into the bulk regions, causing a reduction of the tritium concentration in the sub-surface layers of the samples. All of the observed β-ray induced X-ray spectra could be reproduced well by computer simulation by assuming respective depth profiles of tritium in the samples. It was confirmed that BIXS is quite useful to analyze the dynamic transport behavior of tritium in materials.