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Proceedings Paper

Measurement of reaction-in-flight neutrons using thulium activation at the National Ignition Facility
Author(s): G. P. Grim; R. Rundberg; M. M. Fowler; A. C. Hayes; G. Jungman; M. Boswell; A. Klein; J. Wilhelmy; A. Tonchev; C. B. Yeamans
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Paper Abstract

We report on the first observation of tertiary reaction-in-flight (RIF) neutrons produced in compressed deuterium and tritium filled capsules using the National Ignition Facility at Lawrence Livermore National Laboratory, Livermore, CA. RIF neutrons are produced by third-order, out of equilibrium (“in-flight”) fusion reactions, initiated by primary fusion products. The rate of RIF reactions is dependent upon the range of the elastically scattered fuel ions and therefore a diagnostic of Coulomb physics within the plasma. At plasma temperatures of ∼5 keV, the presence of neutrons with kinetic energies greater than 15 MeV is a unique signature for RIF neutron production. The reaction 169Tm(n,3n)167Tm has a threshold of 15.0 MeV, and a unique decay scheme making it a suitable diagnostic for observing RIF neutrons. RIF neutron production is quantified by the ratio of 167Tm/168Tm observed in a 169Tm foil, where the reaction 169Tm(n,2n)168Tm samples the primary neutron fluence. Averaged over 4 implosions1–4 at the NIF, the 167Tm/168Tm ratio is measured to be 1.5 ± 0.3 x 10−5, leading to an average ratio of RIF to primary neutron ratio of 1.0 ± 0.2 x 10−4. These ratios are consistent with the predictions for charged particle stopping in a quantum degenerate plasma.

Paper Details

Date Published: 15 September 2014
PDF: 13 pages
Proc. SPIE 9211, Target Diagnostics Physics and Engineering for Inertial Confinement Fusion III, 921108 (15 September 2014); doi: 10.1117/12.2066249
Show Author Affiliations
G. P. Grim, Los Alamos National Lab. (United States)
R. Rundberg, Los Alamos National Lab. (United States)
M. M. Fowler, Los Alamos National Lab. (United States)
A. C. Hayes, Los Alamos National Lab. (United States)
G. Jungman, Los Alamos National Lab. (United States)
M. Boswell, Lawrence Livermore National Lab. (United States)
A. Klein, Los Alamos National Lab. (United States)
J. Wilhelmy, Los Alamos National Lab. (United States)
A. Tonchev, Lawrence Livermore National Lab. (United States)
C. B. Yeamans, Lawrence Livermore National Lab. (United States)


Published in SPIE Proceedings Vol. 9211:
Target Diagnostics Physics and Engineering for Inertial Confinement Fusion III
Perry M. Bell; Gary P. Grim, Editor(s)

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