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Title: Design and Construction of a Gamma Reaction History Diagnostic for the National Ignition Facility

Abstract

Gas Cherenkov detectors have been used to convert fusion gammas into photons to achieve gamma reaction history (GRH) measurements. These gas detectors include a converter, pressurized gas volume, relay optics, and a photon detector. A novel design for the National Ignition Facility (NIF) using 90º Off-Axis Parabolic mirrors efficiently collects signal from fusion gammas with 8-ps time dispersion.1 Fusion gammas are converted to Compton electrons, which generate broadband Cherenkov light (our response is from 250 to 700 nm) in a pressurized gas cell. This light is relayed into a high-speed detector using three parabolic mirrors. The detector optics collect light from a 125-mm-diameter by 600-mm-long interchangeable gas (CO2 or SF6) volume. Because light is collected from source locations throughout the gas volume, the detector is positioned at the stop position rather than at an image position. The stop diameter and its position are independent of the light-generation locations along the gas cell. This design incorporates a fixed time delay that allows the detector to recover from prompt radiation. Optical ray tracings demonstrate how light can be collected from different angled trajectories of the Compton electrons as they traverse the gas volume. A Monte Carlo model of the conversion process frommore » gammas to Cherenkov photons is used to generate photon trajectories. The collection efficiencies for different gamma energies are evaluated. At NIF, a cluster of four channels will allow for increased dynamic range, as well as different gamma energy thresholds. This GRH design is compared to a gas Cherenkov detector that utilizes a Cassegrain reflector now used at the OMEGA laser facility. 1. R. M. Malone, H. W. Herrmann, W. Stoeffl, J. M. Mack, C. S. Young, “Gamma bang time/reaction history diagnostics for the National Ignition Facility using 90º off-axis parabolic mirrors,” Rev. Sci. Instrum. 79, 10E532 (2008).« less

Authors:
Publication Date:
Research Org.:
National Security Technologies, LLC (United States)
Sponsoring Org.:
USDOE National Nuclear Security Administration (NA)
OSTI Identifier:
961544
Report Number(s):
DOE/NV/25946-732
TRN: US0903148
DOE Contract Number:  
DE-AC52-06NA25946
Resource Type:
Conference
Resource Relation:
Conference: 36th International Conference on Plasma Science (ICOPS) and 23rd Symposium on Fusion Engineering (SOFE); San Diego, California; May 31-June 5, 2009
Country of Publication:
United States
Language:
English
Subject:
46 INSTRUMENTATION RELATED TO NUCLEAR SCIENCE AND TECHNOLOGY; CHERENKOV COUNTERS; CONSTRUCTION; DESIGN; ELECTRONS; LASERS; MIRRORS; OPTICS; PHOTONS; PHOTONUCLEAR REACTIONS; PLASMA; TIME DELAY; TRAJECTORIES; US NATIONAL IGNITION FACILITY; gamma reaction history, NIF, National Ignition Facility

Citation Formats

R.M. Malone, B.C. Cox, B.C. Frogget, M.I. Kaufman, T.W. Tunnell, H.W. Herrmann, S.C. Evans, J.M. Mack, C.S. Young, and Stoeffl, W. Design and Construction of a Gamma Reaction History Diagnostic for the National Ignition Facility. United States: N. p., 2009. Web.
R.M. Malone, B.C. Cox, B.C. Frogget, M.I. Kaufman, T.W. Tunnell, H.W. Herrmann, S.C. Evans, J.M. Mack, C.S. Young, & Stoeffl, W. Design and Construction of a Gamma Reaction History Diagnostic for the National Ignition Facility. United States.
R.M. Malone, B.C. Cox, B.C. Frogget, M.I. Kaufman, T.W. Tunnell, H.W. Herrmann, S.C. Evans, J.M. Mack, C.S. Young, and Stoeffl, W. Fri . "Design and Construction of a Gamma Reaction History Diagnostic for the National Ignition Facility". United States. https://www.osti.gov/servlets/purl/961544.
@article{osti_961544,
title = {Design and Construction of a Gamma Reaction History Diagnostic for the National Ignition Facility},
author = {R.M. Malone, B.C. Cox, B.C. Frogget, M.I. Kaufman, T.W. Tunnell and H.W. Herrmann, S.C. Evans, J.M. Mack, C.S. Young and Stoeffl, W},
abstractNote = {Gas Cherenkov detectors have been used to convert fusion gammas into photons to achieve gamma reaction history (GRH) measurements. These gas detectors include a converter, pressurized gas volume, relay optics, and a photon detector. A novel design for the National Ignition Facility (NIF) using 90º Off-Axis Parabolic mirrors efficiently collects signal from fusion gammas with 8-ps time dispersion.1 Fusion gammas are converted to Compton electrons, which generate broadband Cherenkov light (our response is from 250 to 700 nm) in a pressurized gas cell. This light is relayed into a high-speed detector using three parabolic mirrors. The detector optics collect light from a 125-mm-diameter by 600-mm-long interchangeable gas (CO2 or SF6) volume. Because light is collected from source locations throughout the gas volume, the detector is positioned at the stop position rather than at an image position. The stop diameter and its position are independent of the light-generation locations along the gas cell. This design incorporates a fixed time delay that allows the detector to recover from prompt radiation. Optical ray tracings demonstrate how light can be collected from different angled trajectories of the Compton electrons as they traverse the gas volume. A Monte Carlo model of the conversion process from gammas to Cherenkov photons is used to generate photon trajectories. The collection efficiencies for different gamma energies are evaluated. At NIF, a cluster of four channels will allow for increased dynamic range, as well as different gamma energy thresholds. This GRH design is compared to a gas Cherenkov detector that utilizes a Cassegrain reflector now used at the OMEGA laser facility. 1. R. M. Malone, H. W. Herrmann, W. Stoeffl, J. M. Mack, C. S. Young, “Gamma bang time/reaction history diagnostics for the National Ignition Facility using 90º off-axis parabolic mirrors,” Rev. Sci. Instrum. 79, 10E532 (2008).},
doi = {},
journal = {},
number = ,
volume = ,
place = {United States},
year = {2009},
month = {6}
}

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