Applicability of β-ray-induced X-ray spectrometry to in situ measurements of tritium retention in plasma-facing materials in ITER

Applicability of β-ray-induced X-ray spectrometry (BIXS) for in situ measurements of tritium retention by plasma-facing materials in ITER was examined using two γ-emitters and a divertor tile with metallic supports employed during D–T fusion experiments in JET. Measurements of the tile with a γ-emitter showed that the presence of the γ-field has no influence in the shape of the β-ray-induced X-ray spectra, although the whole intensity in the observed energy region was dependent on radioactivity of the γ-emitters. To simulate more accurately the in-vessel environment of PFMs, one of the divertor tiles with metallic supports was subjected to BIXS measurements. Although the metallic supports were gamma active, no significant effect was observed on the recorded X-ray spectrum. These results clearly indicate that BIXS can be applied to in situ measurements of tritium retention by PFMs with a simple shielding of the X-ray detector.