D-T gamma-to-neutron branching ratio determined from inertial confinement fusion plasmas

Journal Article · Tue May 15 00:00:00 EDT 2012 · Physics of Plasmas

DOI:https://doi.org/10.1063/1.4718291· OSTI ID:22072417

Kim, Y; Mack, J M; Herrmann, H W; Young, C S; Hale, G M; Caldwell, S; Hoffman, N M; Evans, S C; Sedillo, T J; McEvoy, A; Langenbrunner, J; Hsu, H H; Huff, M A; Batha, S ^[1]; Horsfield, C J; Rubery, M S; Garbett, W J ^[2]; Stoeffl, W; Grafil, E; Bernstein, L ^[3] ; others, and

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1. Los Alamos National Laboratory, Los Alamos, New Mexico 87545 (United States)
2. Atomic Weapons Establishment, Aldermaston, Reading, Berkshire RG7 4PR (United Kingdom)
3. Lawrence Livermore National Laboratory, Livermore, California 94550 (United States)

A new deuterium-tritium (D-T) fusion gamma-to-neutron branching ratio [{sup 3}H(d,{gamma}){sup 5}He/{sup 3}H(d,n){sup 4}He] value of (4.2 {+-} 2.0) Multiplication-Sign 10{sup -5} was recently reported by this group [Y. Kim et al. Phys. Rev. C (submitted)]. This measurement, conducted at the OMEGA laser facility located at the University of Rochester, was made for the first time using inertial confinement fusion (ICF) plasmas. Neutron-induced backgrounds are significantly reduced in these experiments as compared to traditional beam-target accelerator-based experiments due to the short pulse nature of ICF implosions and the use of gas Cherenkov {gamma}-ray detectors with fast temporal responses and inherent energy thresholds. It is expected that this ICF-based measurement will help resolve the large and long-standing inconsistencies in previously reported accelerator-based values, which vary by a factor of approximately 30. The reported value at ICF conditions was determined by averaging the results of two methods: (1) a direct measurement of ICF D-T {gamma}-ray and neutron emissions using absolutely calibrated detectors and (2) a separate cross-calibration against the better known D-{sup 3}He gamma-to-proton branching ratio [{sup 3}He(d, {gamma}){sup 5}Li/{sup 3}He(d,p){sup 4}He]. Here we include a detailed explanation of these results, and introduce as a corroborative method an in-situ{gamma}-ray detector calibration using neutron-induced {gamma}-rays. Also, by extending the established techniques to two additional series of implosions with significantly different ion temperatures, we test the branching ratio dependence on ion temperature. The data show a D-T branching ratio is nearly constant over the temperature range 2-9 keV. These studies motivate further investigation into the {sup 5}He and {sup 5}Li systems resulting from D-T and D-{sup 3}He fusion, respectively, and result in improved ICF {gamma}-ray reaction history diagnosis at the National Ignition Facility.

• OSTI ID: 22072417
• Journal Information: Physics of Plasmas, Vol. 19, Issue 5; Other Information: (c) 2012 American Institute of Physics; Country of input: International Atomic Energy Agency (IAEA); ISSN 1070-664X
• Country of Publication: United States
• Language: English

Related Subjects

70 PLASMA PHYSICS AND FUSION TECHNOLOGY
ACCELERATORS
BRANCHING RATIO
CALIBRATION
CHERENKOV COUNTERS
DEUTERIUM
GAMMA RADIATION
HELIUM 3
HELIUM 4
HELIUM 5
ICF DEVICES
IMPLOSIONS
INERTIAL CONFINEMENT
ION TEMPERATURE
LITHIUM 5
NEUTRON EMISSION
NEUTRONS
OMEGA FACILITY
PROTONS
TRITIUM
US NATIONAL IGNITION FACILITY