Cross-calibrations of the D-T γ-to-neutron and D-³He γ-to-proton branching ratios against the ¹²C(n,n’γ)¹²C reaction

The deuterium-tritium (D-T) γ-to-neutron branching ratio (³H(d,γ)⁵He/³H(d,n)⁴He) has been determined previously in beam-target based experiments as well as in inertial confinement fusion (ICF) experiments. There is however large discrepancies in the obtained results. A benefit of ICF based measurements is the ability to achieve lower center of mass energies as compared to accelerators, and temporally separate the signal from neutron induced backgrounds. A more precise value for the branching ratio based on data taken at the OMEGA facility has been determined which relies on a cross-calibration against the better known ¹²C neutron inelastic scattering cross section (¹²C(n,n’γ)¹²C) in a puck-based experiment involving the Gas Cherenkov Detector (GCD-3). A D-T branching ratio value of (4.6 ± 0.6) × 10⁻⁵ is determined by this method. [1] The results of a more recent and optimized experiment to measure the D-T branching ratio are discussed as well as a measurement of the D-³He -to-proton branching ratio, using similar techniques, to provide better precision than reported by previous experiments which are limited to 33%.

[1] J. Jeet at al., Inertial-confinement fusion-plasma-based cross-calibration of the deuterium-tritium γ-to-neutron branching ratio, Phys. Rev. C. 104, 054611 (2021).