Detection of absorbed neutrons through determination of rhenium content in tungsten with laser induced fast pulse discharge

Abstract

The diagnostics of the first wall of future fusion reactors provides a major source of information about the state of the machine and the expected lifetime of the first wall components. As the absorption of neutrons can cause induced radioactivity of the first wall tiles and produce significant structural changes to material, it is of the essence to monitor the amount of absorbed neutrons. One possibility to monitor them is via nuclear transmutation reaction where tungsten absorbs neutron and creates rhenium core. Therefore by assessing the amount of rhenium present in the material, information about neutron irradiation conditions can be deduced. Hence in this work, in order to assess the concentration of rhenium, Laser Induced Breakdown Spectroscopy (LIBS) combined with Fast Pulse Discharge (FPD) was used. The main achievement of this work is the amplification of line intensity and signal to noise ratio compared to the classical LIBS setup at reduced pressure which enables detection of Re in samples with less than 0.1% at of Re. With synergistic use of LIBS and FPD, ie. Laser Induced Fast Pulse Discharge (LIFPD), significantly enhanced Limit Of Detection (LOD) is obtained compared to the previously reported results. This result is of particular importance since only small amounts of rhenium are expected to be found in the first wall tiles, therefore making this approach suitable for this type of diagnostics.