First Demonstration of laser induced breakdown spectroscopy using remote handling for in-vessel analysis of JET components

• Feasibility of LIBS for measuring fuel retention was demonstrated in JET using a remote handling system. • A novel LIBS system was developed at ENEA and optimised by Forschungszentrum Jülich. • 840 different spatial locations on the main wall and divertor area were investigated. • H α and D α components were only partially separated due to Stark broadening. • Overall, the T amount in PFCs was low due to the efficient clean-up campaign. The feasibility of laser-induced breakdown spectroscopy (LIBS) for measuring fuel retention was demonstrated for the first time in a tokamak operating with tritium using a remotely controlled in-situ application in JET. In JET as well as in future fusion reactors such as ITER and DEMO, thick co-deposited layers will be formed on the inner wall during extended plasma operations. Experiments in present-day fusion devices indicate that these layers consist of eroded plasma-facing materials, various impurities and plasma fuel species such as deuterium and tritium. Accumulation of radioactive tritium in the reactor vacuum vessel is a particularly critical safety issue requiring active monitoring. LIBS is one of the few techniques available for monitoring the tritium content and the composition of co-deposited layers during maintenance breaks [ 1 ]. This paper will provide an overview of the LIBS experiment that was performed post DTE3 campaign, and D and H cleanup at JET in October 2024. 840 different spatial locations on the main wall and divertor area were investigated, with measurements of more than 100 laser pulses per location executed to ensure good depth resolution.