Trace xenon detection in ambient helium by double-pulse laser-induced breakdown spectroscopy

Safe operation of next-generation nuclear reactors is contingent on developing and effectively operating new diagnostics methods. For helium-cooled fast reactors, one important safety concern is the onset of fuel-cladding failure, which could be detected from the increased concentration of mobile fission fragments such as xenon in the helium coolant. In a previous study [Burger et al., JAAS, 2021, 36, 824], we demonstrated that laser-induced breakdown spectroscopy (LIBS) is a viable candidate for sensitive xenon detection in helium, offering a limit of detection on the order of 0.2 μmol mol⁻¹ for 10⁴ laser shots. Here, we demonstrate that double-pulse LIBS enhances the xenon signal by approximately 14× at a concentration of 1 μmol mol⁻¹ in an ambient helium environment, which results in significantly improved sensitivity. Additionally, we examine the effect of relative energy in two laser pulses, interpulse delay, and laser polarization on the xenon signal enhancement. These results further motivate the development of LIBS sensors for this application.