An inertial confinement fusion plasma based cross-calibration of the deuterium-tritium γ-to-neutron branching ratio*

The deuterium-tritium (D-T) γ-to-neutron branching ratio [³H(d,γ)⁵He/³H(d,n)⁴He] has been determined previously under inertial confinement fusion (ICF) conditions and in beam-target based experiments. In the former case, neutron-induced backgrounds are mitigated compared to the latter due to the short pulse nature of ICF implosions and the use of gas Cherenkov γ-ray detectors. An added benefit of ICF based measurements is the ability to achieve lower center of mass energies as compared to accelerators. Previous ICF based experiments however report a large uncertainty in the D-T γ-to-neutron branching ratio of ~48%, which arises from the necessity of an absolute detector calibration and/or a cross calibration against the D-³He γ-to-proton branching ratio. A more precise value for the branching ratio based on data taken at the OMEGA laser facility is reported here, which relies on a cross-calibration against the better known ¹²C neutron inelastic scattering cross section. A D-T branching ratio value of (4.81 ± 0.61) × 10⁻⁵ is determined by this method.