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Title: Improved inertial confinement fusion gamma reaction history 12C gamma-ray signal by direct subtraction

Abstract

The Gamma Reaction History Diagnostic (GRH) located at the National Ignition Facility (NIF) measures time resolved gamma rays released from inertial confinement fusion experiments by converting emitted gamma rays into Cherenkov light. Imploded capsules have a bright 4.4 MeV gamma ray from fusion neutrons inelastically scattering with carbon atoms in the remaining ablator. The strength of 4.4 MeV gamma ray line is proportional to the capsule’s carbon ablator areal density and can be used to understand the dynamics and energy budget of a carbon-based ablator capsule implosion. Historically, the GRH’s four gas cells use the energy thresholding from the Cherenkov process to forward fit an estimation of the experiment’s complete gamma ray spectrum by modeling the surrounding environment in order to estimate the 4.4 MeV neutron induced carbon gamma ray signal. However, the high number of variables, local minima and uncertainties in detector sensitivities and relative timing had prevented routine use of the forward fit to generate carbon areal density measurements. A new, more straightforward, process of direct subtraction of deconvolved signals was developed to simplify the extraction of the carbon areal density. Beryllium capsules are used as a calibration to measure a capsule environment with no carbon signal. Thismore » is then used to appropriately subtract and isolate the carbon signal on shots with carbon ablators. The subtraction algorithm achieves good results across all major capsule campaigns, achieving similar results to the forward fit. This method is now used routinely to measure carbon areal density for NIF shots.« less

Authors:
ORCiD logo [1]; ORCiD logo [1]; ORCiD logo [1]; ORCiD logo [1]; ORCiD logo [1]
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  1. Los Alamos National Lab. (LANL), Los Alamos, NM (United States)
Publication Date:
Research Org.:
Los Alamos National Lab. (LANL), Los Alamos, NM (United States)
Sponsoring Org.:
USDOE
OSTI Identifier:
1574754
Alternate Identifier(s):
OSTI ID: 1573424
Report Number(s):
LA-UR-19-21506
Journal ID: ISSN 0034-6748
Grant/Contract Number:  
89233218CNA000001; AC52-06NA25396
Resource Type:
Accepted Manuscript
Journal Name:
Review of Scientific Instruments
Additional Journal Information:
Journal Volume: 90; Journal Issue: 11; Journal ID: ISSN 0034-6748
Publisher:
American Institute of Physics (AIP)
Country of Publication:
United States
Language:
English
Subject:
47 OTHER INSTRUMENTATION

Citation Formats

Meaney, Kevin Daniel, Kim, Yong Ho, Herrmann, Hans W., Geppert-Kleinrath, Hermann, and Hoffman, Nelson M. Improved inertial confinement fusion gamma reaction history 12C gamma-ray signal by direct subtraction. United States: N. p., 2019. Web. doi:10.1063/1.5092501.
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Meaney, Kevin Daniel, Kim, Yong Ho, Herrmann, Hans W., Geppert-Kleinrath, Hermann, & Hoffman, Nelson M. Improved inertial confinement fusion gamma reaction history 12C gamma-ray signal by direct subtraction. United States. doi:10.1063/1.5092501.
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Meaney, Kevin Daniel, Kim, Yong Ho, Herrmann, Hans W., Geppert-Kleinrath, Hermann, and Hoffman, Nelson M. Thu . "Improved inertial confinement fusion gamma reaction history 12C gamma-ray signal by direct subtraction". United States. doi:10.1063/1.5092501.
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@article{osti_1574754,
title = {Improved inertial confinement fusion gamma reaction history 12C gamma-ray signal by direct subtraction},
author = {Meaney, Kevin Daniel and Kim, Yong Ho and Herrmann, Hans W. and Geppert-Kleinrath, Hermann and Hoffman, Nelson M.},
abstractNote = {The Gamma Reaction History Diagnostic (GRH) located at the National Ignition Facility (NIF) measures time resolved gamma rays released from inertial confinement fusion experiments by converting emitted gamma rays into Cherenkov light. Imploded capsules have a bright 4.4 MeV gamma ray from fusion neutrons inelastically scattering with carbon atoms in the remaining ablator. The strength of 4.4 MeV gamma ray line is proportional to the capsule’s carbon ablator areal density and can be used to understand the dynamics and energy budget of a carbon-based ablator capsule implosion. Historically, the GRH’s four gas cells use the energy thresholding from the Cherenkov process to forward fit an estimation of the experiment’s complete gamma ray spectrum by modeling the surrounding environment in order to estimate the 4.4 MeV neutron induced carbon gamma ray signal. However, the high number of variables, local minima and uncertainties in detector sensitivities and relative timing had prevented routine use of the forward fit to generate carbon areal density measurements. A new, more straightforward, process of direct subtraction of deconvolved signals was developed to simplify the extraction of the carbon areal density. Beryllium capsules are used as a calibration to measure a capsule environment with no carbon signal. This is then used to appropriately subtract and isolate the carbon signal on shots with carbon ablators. The subtraction algorithm achieves good results across all major capsule campaigns, achieving similar results to the forward fit. This method is now used routinely to measure carbon areal density for NIF shots.},
doi = {10.1063/1.5092501},
journal = {Review of Scientific Instruments},
number = 11,
volume = 90,
place = {United States},
year = {2019},
month = {11}
}
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DOI:  10.1063/1.5092501
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