The sensitivity of NRA for deuterium quantification in Li-based materials

Abstract

The use of lithium (Li) and Li-based materials for liquid metal applications is a promising solution to protect solid plasma facing materials from dense power flows in operative fusion scenarios. The recovery of the liquid materials and the affinity of lithium to retain hydrogen motivates an extensive research of the retained deuterium amounts, which is commonly investigated by Nuclear Reaction Analysis (NRA) by resolving the ²H(³He,p)⁴He reaction yields. Nevertheless, the incidence of ³He ion beams induces other competing nuclear reactions such as ⁶Li(³He,p_i)⁸Be, ⁷Li(³He,p_i)⁹Be and ⁷Li(³He,d_i)⁸Be, with related particle yields visible in the spectra. Particularly, the energy width of the p₁ emission of the ⁶Li(³He,p_i)⁸Be reaction is large (about 1.75 MeV), and the ⁶Li(³He,p_i)⁸Be yield becomes superimposed to the ²H(³He,p₀)⁴He one. Even so, deuterium quantification is possible to achieve due to the cross-sections of both proton emissions, being the detection limits widely dependent of the Li contents, of the energy of the incident ³He ion beam and of the energy resolution of detection system. In the present experiment, Li-Sn alloys were used as Li-based material. The case of pure Li was extrapolated from the experimental data. For a standard analysis with accumulated charges of 5 μC in the collected spectra, minimum detectable amounts within the range from ∼1 × 10¹⁵ at./cm² to ∼1 × 10¹⁶ at./cm² were predicted for all the studied examples.