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Title: High-resolution spectroscopy used to measure inertial confinement fusion neutron spectra on Omega (invited)

Abstract

The areal density ({rho}R) of cryogenic DT implosions on Omega is inferred by measuring the spectrum of neutrons that elastically scatter off the dense deuterium (D) and tritium (T) fuel. Neutron time-of-flight (nTOF) techniques are used to measure the energy spectrum with high resolution. High signal-to-background data has been recorded on cryogenic DT implosions using a well-collimated 13.4-m line of sight and an nTOF detector with an advanced liquid scintillator compound. An innovative method to analyze the elastically scattered neutron spectra was developed using well-known cross sections of the DT nuclear reactions. The estimated areal densities are consistent with alternative {rho}R measurements and 1-D simulations.

Authors:
; ; ; ; ; ; ; ; ;  [1]; ;  [2];  [3]
  1. Laboratory for Laser Energetics, University of Rochester, Rochester, New York 14623-1299 (United States)
  2. Plasma Science and Fusion Center, Massachusetts Institute of Technology, Cambridge, Massachusetts 02139-4307 (United States)
  3. Constellation Energy Nuclear Group, Ontario, New York 14519 (United States)
Publication Date:
OSTI Identifier:
22093886
Resource Type:
Journal Article
Resource Relation:
Journal Name: Review of Scientific Instruments; Journal Volume: 83; Journal Issue: 10; Other Information: (c) 2012 American Institute of Physics; Country of input: International Atomic Energy Agency (IAEA)
Country of Publication:
United States
Language:
English
Subject:
73 NUCLEAR PHYSICS AND RADIATION PHYSICS; 46 INSTRUMENTATION RELATED TO NUCLEAR SCIENCE AND TECHNOLOGY; CROSS SECTIONS; DEUTERIUM; ENERGY SPECTRA; INERTIAL CONFINEMENT; LIQUID SCINTILLATION DETECTORS; NEUTRON DETECTION; NEUTRON SPECTRA; NEUTRON SPECTROMETERS; NEUTRONS; NUCLEAR REACTIONS; PLASMA DENSITY; PLASMA DIAGNOSTICS; SIMULATION; SPECTROSCOPY; THERMONUCLEAR REACTORS; TIME-OF-FLIGHT METHOD; TIME-OF-FLIGHT SPECTROMETERS; TRITIUM

Citation Formats

Forrest, C. J., Radha, P. B., Glebov, V. Yu., Goncharov, V. N., Knauer, J. P., Pruyne, A., Romanofsky, M., Sangster, T. C., Shoup, M. J. III, Stoeckl, C., Casey, D. T., Gatu-Johnson, M., and Gardner, S. High-resolution spectroscopy used to measure inertial confinement fusion neutron spectra on Omega (invited). United States: N. p., 2012. Web. doi:10.1063/1.4742926.
Forrest, C. J., Radha, P. B., Glebov, V. Yu., Goncharov, V. N., Knauer, J. P., Pruyne, A., Romanofsky, M., Sangster, T. C., Shoup, M. J. III, Stoeckl, C., Casey, D. T., Gatu-Johnson, M., & Gardner, S. High-resolution spectroscopy used to measure inertial confinement fusion neutron spectra on Omega (invited). United States. doi:10.1063/1.4742926.
Forrest, C. J., Radha, P. B., Glebov, V. Yu., Goncharov, V. N., Knauer, J. P., Pruyne, A., Romanofsky, M., Sangster, T. C., Shoup, M. J. III, Stoeckl, C., Casey, D. T., Gatu-Johnson, M., and Gardner, S. 2012. "High-resolution spectroscopy used to measure inertial confinement fusion neutron spectra on Omega (invited)". United States. doi:10.1063/1.4742926.
@article{osti_22093886,
title = {High-resolution spectroscopy used to measure inertial confinement fusion neutron spectra on Omega (invited)},
author = {Forrest, C. J. and Radha, P. B. and Glebov, V. Yu. and Goncharov, V. N. and Knauer, J. P. and Pruyne, A. and Romanofsky, M. and Sangster, T. C. and Shoup, M. J. III and Stoeckl, C. and Casey, D. T. and Gatu-Johnson, M. and Gardner, S.},
abstractNote = {The areal density ({rho}R) of cryogenic DT implosions on Omega is inferred by measuring the spectrum of neutrons that elastically scatter off the dense deuterium (D) and tritium (T) fuel. Neutron time-of-flight (nTOF) techniques are used to measure the energy spectrum with high resolution. High signal-to-background data has been recorded on cryogenic DT implosions using a well-collimated 13.4-m line of sight and an nTOF detector with an advanced liquid scintillator compound. An innovative method to analyze the elastically scattered neutron spectra was developed using well-known cross sections of the DT nuclear reactions. The estimated areal densities are consistent with alternative {rho}R measurements and 1-D simulations.},
doi = {10.1063/1.4742926},
journal = {Review of Scientific Instruments},
number = 10,
volume = 83,
place = {United States},
year = 2012,
month =
}
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  • Here, we present results from the comparison of high-resolution three-dimensional (3D) simulations with data from the implosions of inertial confinement fusion capsules with separated reactants performed on the OMEGA laser facility. Each capsule, referred to as a “CD Mixcap,” is filled with tritium and has a polystyrene (CH) shell with a deuterated polystyrene (CD) layer whose burial depth is varied. In these implosions, fusion reactions between deuterium and tritium ions can occur only in the presence of atomic mix between the gas fill and shell material. The simulations feature accurate models for all known experimental asymmetries and do not employmore » any adjustable parameters to improve agreement with experimental data. Simulations are performed with the RAGE radiation-hydrodynamics code using an Implicit Large Eddy Simulation (ILES) strategy for the hydrodynamics. We obtain good agreement with the experimental data, including the DT/TT neutron yield ratios used to diagnose mix, for all burial depths of the deuterated shell layer. Additionally, simulations demonstrate good agreement with converged simulations employing explicit models for plasma diffusion and viscosity, suggesting that the implicit sub-grid model used in ILES is sufficient to model these processes in these experiments. In our simulations, mixing is driven by short-wavelength asymmetries and longer-wavelength features are responsible for developing flows that transport mixed material towards the center of the hot spot. Mix material transported by this process is responsible for most of the mix (DT) yield even for the capsule with a CD layer adjacent to the tritium fuel. Consistent with our previous results, mix does not play a significant role in TT neutron yield degradation; instead, this is dominated by the displacement of fuel from the center of the implosion due to the development of turbulent instabilities seeded by long-wavelength asymmetries. Through these processes, the long-wavelength asymmetries degrade TT yield more than the DT yield and thus bring DT/TT neutron yield ratios into agreement with experiment. Finally, we present a detailed comparison of the flows in 2D and 3D simulations.« less
  • We present results from the comparison of high-resolution three-dimensional (3D) simulations with data from the implosions of inertial confinement fusion capsules with separated reactants performed on the OMEGA laser facility. Each capsule, referred to as a “CD Mixcap,” is filled with tritium and has a polystyrene (CH) shell with a deuterated polystyrene (CD) layer whose burial depth is varied. In these implosions, fusion reactions between deuterium and tritium ions can occur only in the presence of atomic mix between the gas fill and shell material. The simulations feature accurate models for all known experimental asymmetries and do not employ anymore » adjustable parameters to improve agreement with experimental data. Simulations are performed with the RAGE radiation-hydrodynamics code using an Implicit Large Eddy Simulation (ILES) strategy for the hydrodynamics. We obtain good agreement with the experimental data, including the DT/TT neutron yield ratios used to diagnose mix, for all burial depths of the deuterated shell layer. Additionally, simulations demonstrate good agreement with converged simulations employing explicit models for plasma diffusion and viscosity, suggesting that the implicit sub-grid model used in ILES is sufficient to model these processes in these experiments. In our simulations, mixing is driven by short-wavelength asymmetries and longer-wavelength features are responsible for developing flows that transport mixed material towards the center of the hot spot. Mix material transported by this process is responsible for most of the mix (DT) yield even for the capsule with a CD layer adjacent to the tritium fuel. Consistent with our previous results, mix does not play a significant role in TT neutron yield degradation; instead, this is dominated by the displacement of fuel from the center of the implosion due to the development of turbulent instabilities seeded by long-wavelength asymmetries. Through these processes, the long-wavelength asymmetries degrade TT yield more than the DT yield and thus bring DT/TT neutron yield ratios into agreement with experiment. Finally, we present a detailed comparison of the flows in 2D and 3D simulations.« less