Detection of trace rhenium in tungsten by laser-induced breakdown spectroscopy

Tungsten(W) is a leading candidate material for wall materials of fusion reactors in ITER and beyond. Various researches for use of W as a plasma facing material are in progress. In a fusion reactor, W absorbs neutrons and changes to rhenium(Re) via beta decays. Therefore, concentration of transmuted Re in W is a good indicator of neutron irradiation dose to W. This study aims to develop a new diagnostic tool to remotely detect trace amounts of Re in W by Laser-Induced Breakdown Spectroscopy(LIBS) for evaluating the neutron irradiation dose on the fusion reactor wall surfaces.

For experimental samples, pure W, pure Re, and W-Re alloys in which the Re content was varied from 0.1 to 10% were prepared. Samples were placed in an ultra-high vacuum (UHV) chamber, and its surface was irradiated by the third harmonics of Nd:YAG laser to generate ablation plasma. The optical emission of the ablation plasma was observed through a spectrometer having a resolution of 0.1 nm. Some observed peaks were identified based on NIST database. Parameter optimization for improving accuracy of trace Re detection by LIBS was performed and the detection limit of trace amount Re by this method was discussed.