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Proceedings Paper

Engineering architecture of the neutron Time-of-Flight (nToF) diagnostic suite at the National Ignition Facility
Author(s): T. J. Clancy; J. Caggiano; J. McNaney; M. Eckart; M. Moran; V. Y. Glebov; J. Knauer; R. Hatarik; S. Friedrich; R. Zacharias; A. Carpenter; M. J. Shoup; T. Buczek; M. Yeoman; Z. Zeid; N. Zaitseva; B. Talison; J. Worden; B. Rice; T. Duffy; A. Pruyne; K. Marshall
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Paper Abstract

This paper describes the engineering architecture and function of the neutron Time-of-Flight (nToF) diagnostic suite installed on the National Ignition Facility (NIF) at Lawrence Livermore National Laboratory (LLNL). These instruments provide key measures of neutron yield, ion temperature, drift velocity, neutron bang-time, and neutron downscatter ratio. Currently, there are five nToFs on three collimated lines-of-site (LOS) from 18m to 27m from Target Chamber Center, and three positioned 4.5m from TCC, within the NIF Target Chamber but outside the vacuum and confinement boundary by use of re-entrant wells on three other LOS. NIF nToFs measure the time history and equivalent energy spectrum of reaction generated neutrons from a NIF experiment. Neutrons are transduced to electrical signals, which are then carried either by coaxial or Mach-Zehnder transmission systems that feed divider assemblies and fiducially timed digitizing oscilloscopes outside the NIF Target Bay (TB) radiation shield wall. One method of transduction employs a two-stage process wherein a neutron is converted to scintillation photons in hydrogen doped plastic (20x40mm) or bibenzyl crystals (280x1050mm), which are subsequently converted to an electrical signal via a photomultiplier tube or a photo-diode. An alternative approach uses a single-stage conversion of neutrons-to-electrons by use of a thin (0.25 to 2 mm) Chemical Vapor Deposition Diamond (CVDD) disc (2 to 24mm radius) under high voltage bias. In comparison to the scintillator method, CVDDs have fast rise and decay times (<ns), have very low residual tails, are insensitive to shot gammas, and are less sensitive to the neutron signal of interest.

Paper Details

Date Published: 10 September 2014
PDF: 17 pages
Proc. SPIE 9211, Target Diagnostics Physics and Engineering for Inertial Confinement Fusion III, 92110A (10 September 2014); doi: 10.1117/12.2062329
Show Author Affiliations
T. J. Clancy, Lawrence Livermore National Lab. (United States)
J. Caggiano, Lawrence Livermore National Lab. (United States)
J. McNaney, Lawrence Livermore National Lab. (United States)
M. Eckart, Lawrence Livermore National Lab. (United States)
M. Moran, Lawrence Livermore National Lab. (United States)
V. Y. Glebov, Univ. of Rochester (United States)
J. Knauer, Univ. of Rochester (United States)
R. Hatarik, Lawrence Livermore National Lab. (United States)
S. Friedrich, Lawrence Livermore National Lab. (United States)
R. Zacharias, Lawrence Livermore National Lab. (United States)
A. Carpenter, Lawrence Livermore National Lab. (United States)
M. J. Shoup, Univ. of Rochester (United States)
T. Buczek, Univ. of Rochester (United States)
M. Yeoman, Lawrence Livermore National Lab. (United States)
Z. Zeid, Univ. of Rochester (United States)
N. Zaitseva, Lawrence Livermore National Lab. (United States)
B. Talison, Lawrence Livermore National Lab. (United States)
J. Worden, Lawrence Livermore National Lab. (United States)
B. Rice, Univ. of Rochester (United States)
T. Duffy, Univ. of Rochester (United States)
A. Pruyne, Univ. of Rochester (United States)
K. Marshall, Univ. of Rochester (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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