Determination of the deuterium-tritium branching ratio based on inertial confinement fusion implosions

The deuterium-tritium (D-T) {γ}-to-neutron branching ratio [³H(d,{γ})⁵He/³H(d,n)⁴He] was determined under inertial confinement fusion (ICF) conditions, where the center-of-mass energy of 14--24 keV is lower than that in previous accelerator-based experiments. A D-T branching ratio value of (4.2 ±{} 2.0) ×{} 10^-5 was determined by averaging the results of two methods: (1) a direct measurement of ICF D-T {γ}-ray and neutron emissions using absolutely calibrated detectors, and (2) a separate cross-calibration against the D-³He {γ}-to-proton branching ratio [³He(d,{γ})⁵Li/³He(d,p)⁴He]. Neutron-induced backgrounds were significantly reduced as compared to traditional beam-target accelerator-based experiments due to the short pulse nature of ICF implosions and the use of gas Cherenkov {γ}-ray detectors with fast temporal responses and inherent energy thresholds. These measurements of the D-T branching ratio in an ICF environment test several theoretical assumptions about the nature of A = 5 systems, including the dominance of the 3/2⁺ resonance at low energies, the presence of the broad first excited state of ⁵He in the spectra, and the charge-symmetric nature of the capture processes in the mirror systems ⁵He and ⁵Li.