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

Abstract

The D-T gamma-to-neutron branching ratio (3 H(d,γ) 5 He/ 3 H(d,n) 4 He) has been determined at inertial confinement fusion (ICF) conditions, where the center-of-mass energy of 14-24 keV is lower than 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-3 He gamma-to-proton branching ratio (3 He(d,γ) 5 Li/ 3 He(d,p) 4 He). Neutron-induced backgrounds are 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 5 He in the spectra, and the charge-symmetric nature of the capture processes in the mirror systems 5 He and 5 Li.

Thermonuclear fusion rates for tritium + deuterium using Bayesian methods

“…In other words, for the exceptionally broad low-energy resonance in 3 H(d,n) 4 He, one cannot chose the boundary condition parameter, B c = S c (E r ), so that the level shift is zero at the location of the maximum of either |S dn | 2 , σ, or S bare (E), and at the same time expect the "center of the resonance", E r , to equal the eigenvalue E 0 (see Section III). 2 For example, consider again the blue curve shown in 2 Jarmie, Brown and Hardekopf [11] state that they "chose Bc so that the level shifts ∆c are zero near the peak of the S function, which results in the level energy E λ being close to the c.m. energy at which the S function peaks."…”

“…The cross section of the 3 H(d,n) 4 He reaction has a large Q-value of 17.6 MeV, and a large cross section that peaks at ≈ 5 barn near a deuteron (triton) bombarding energy of 105 keV (164 keV). For these reasons, the 3 H(d,n) 4 He reaction will most likely fuel the first magnetic and inertial confinement fusion reactors for commercial energy production [1,2]. The reactors are expected to operate in the thermal energy range of kT= 1 − 30 keV, corresponding to temperatures of T= 12 − 350 MK.…”

Dynamic high energy density plasma environments at the National Ignition Facility for nuclear science research

“…The time history of the nuclear DT fusion reaction (burn), the evolution of the ignition to peak burn and beyond, is most promptly determined by monitoring the DT fusion gammas that have primary peak energy at 16.7 MeV with high time resolution. The gammas have no time-of-flight dispersion along their flight path; the dynamic range, however, is yield limited because of the 4×10 −5 branching ratio of DT fusion gammas to the 14.1 MeV neutron emission [94].…”

“…Of special interest in the work described here is the use of the time-integrated 4.4 MeV 12 C γ emission to fit the hydrocarbon areal density in the context of this model and thereby derive a better qualitative understanding of the stagnation conditions. Constraints for the ablator areal density arise from estimates of the remaining hydrocarbon ablator mass [165,166] and the ablator mass mixed into the burning core [167]. In the case of the highyield series of implosions [164], very little ablator mix was observed in the burning core, implying that the remaining ablator material is either located in a compressed shell around the DT fuel assembly or entrained in the fuel assembly, or both.…”

The Creation and Destruction of Hf-178m2 Isomer by Neutron Interaction

“…Many results were published. One of us (HH) is part of the team studying gamma rays produced in the DT reaction 8,9,10 . The 14.1 MeV neutrons produced in this reaction satisfy our need for a "yes or no" experiment we propose here.…”