Investigation of the D-T γ-to-neutron and D-³He γ-to-proton branching ratios at ICF facilities

The deuterium-tritium (D-T) γ-to-neutron branching ratio (³H(d,γ)⁵He/³H(d,n)⁴He) has been previously measured in several different experimental platforms including beam-target based, inertial confinement fusion (ICF), and magnetic confinement fusion (MCF) plasmas. A unique feature accessible to ICF plasma-based measurements, in contrast to accelerators and magnetic confinement, is the ability to probe lower center of mass energies. ICF based measurements also enable temporal separation of the 𝛾 signal from neutron induced backgrounds which can be problematic in other platforms. 𝛾 detectors at ICF facilities typically utilize the Cherenkov mechanism to attain fast detector response times, a requisite for the inherently short duration of ICF implosions. Recent measurements of the branching ratio exploit the better known ¹²C neutron inelastic scattering cross section (¹²C(n,n’𝛾)¹²C), in puck-based experiments, to absolutely calibrate the 𝛾 detectors. [1-2] A recent MCF based experiment utilizes scintillator-based detectors, with 𝛾 energy resolution, to determine both the shape of the gamma spectrum resulting from D-T fusion as well as the branching ratio. [3-4] There however remains discrepancies in the obtained results across the different experiments. In this work, recent experiments to measure the D-T γ-to-neutron and D-³He 𝛾-to-proton branching ratios, performed at ICF facilities, will be discussed along with preliminary results.