Neutron elastic recoil detection for hydrogen isotope analysis in fusion materials

The neutron elastic recoil detection analysis (NERDA) using a 14.2 MeV neutron beam has been developed to measure depth profiles of hydrogen isotopes up to several hundred micrometers under low background conditions. Results of a proof-of-principle experiment using polyethylene and deuterated polyethylene samples were presented. The detected energy spread due to the geometrical configuration was corrected to estimate depth profiles by an unfolding technique based on the iterative Bayes’ estimation. Hydrogen isotope depth profiles in the inner baffle plate of JT-60U were also measured as an application of NERDA. The hydrogen profile from the surface to 800 μm had three components, while a few counts of deuterium were detected. The detection limit of about 60 ppm was deduced for deuterium.