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Title: Bremsstrahlung x-ray generation for high optical depth radiography applications on the National Ignition Facility [Bremsstrahlung x-ray generation for opacity radiography applications on the National Ignition Facility]

Abstract

Here, we have tested a set of x-ray sources for use as probes of highly attenuating, laser-driven experiments on the National Ignition Facility (NIF). Unlike traditional x-ray sources that optimize for a characteristic atomic transition (often the n = 2 → n = 1 transition in ionized, He-like atoms), the design presented here maximizes the total photon flux by optimizing for intense, broadband Bremsstrahlung radiation. Three experiments were performed with identical targets, including a uranium x-ray source foil and a tungsten substrate with a narrow (25 μm wide) collimating slit to produce a quasi-1D x-ray source. Two experiments were performed using 12 beams from the NIF laser, each delivering approximately 46 kJ of laser energy but with different laser spatial profiles. This pair yielded similar temporal x-ray emission profiles, spatial resolution, and inferred hot electron temperature. A third experiment with only 6 beams delivering approximately 25 kJ produced a lower hot electron temperature and significantly lower x-ray flux, as well as poorer spatial resolution. The data suggest that laser pointing jitter may have affected the location and intensity of the emitting plasma, producing an emission volume that was not well centered behind the collimating slit and lower intensity than designed.more » However, the 12-beam design permits x-ray radiography through highly attenuating samples, where lower energy line-emission x-ray sources would be nearly completely attenuated.« less

Authors:
ORCiD logo [1];  [1];  [1]; ORCiD logo [1];  [1];  [1]
  1. Lawrence Livermore National Lab. (LLNL), Livermore, CA (United States)
Publication Date:
Research Org.:
Lawrence Livermore National Lab. (LLNL), Livermore, CA (United States)
Sponsoring Org.:
USDOE National Nuclear Security Administration (NNSA)
OSTI Identifier:
1479065
Alternate Identifier(s):
OSTI ID: 1477213
Report Number(s):
LLNL-JRNL-750922
Journal ID: ISSN 0034-6748; 936604
Grant/Contract Number:  
AC52-07NA27344
Resource Type:
Accepted Manuscript
Journal Name:
Review of Scientific Instruments
Additional Journal Information:
Journal Volume: 89; Journal Issue: 10; Journal ID: ISSN 0034-6748
Publisher:
American Institute of Physics (AIP)
Country of Publication:
United States
Language:
English
Subject:
47 OTHER INSTRUMENTATION

Citation Formats

Huntington, C. M., McNaney, J. M., Gumbrell, E., Krygier, A., Wehrenberg, C., and Park, H. -S. Bremsstrahlung x-ray generation for high optical depth radiography applications on the National Ignition Facility [Bremsstrahlung x-ray generation for opacity radiography applications on the National Ignition Facility]. United States: N. p., 2018. Web. doi:10.1063/1.5039379.
Huntington, C. M., McNaney, J. M., Gumbrell, E., Krygier, A., Wehrenberg, C., & Park, H. -S. Bremsstrahlung x-ray generation for high optical depth radiography applications on the National Ignition Facility [Bremsstrahlung x-ray generation for opacity radiography applications on the National Ignition Facility]. United States. doi:10.1063/1.5039379.
Huntington, C. M., McNaney, J. M., Gumbrell, E., Krygier, A., Wehrenberg, C., and Park, H. -S. Fri . "Bremsstrahlung x-ray generation for high optical depth radiography applications on the National Ignition Facility [Bremsstrahlung x-ray generation for opacity radiography applications on the National Ignition Facility]". United States. doi:10.1063/1.5039379.
@article{osti_1479065,
title = {Bremsstrahlung x-ray generation for high optical depth radiography applications on the National Ignition Facility [Bremsstrahlung x-ray generation for opacity radiography applications on the National Ignition Facility]},
author = {Huntington, C. M. and McNaney, J. M. and Gumbrell, E. and Krygier, A. and Wehrenberg, C. and Park, H. -S.},
abstractNote = {Here, we have tested a set of x-ray sources for use as probes of highly attenuating, laser-driven experiments on the National Ignition Facility (NIF). Unlike traditional x-ray sources that optimize for a characteristic atomic transition (often the n = 2 → n = 1 transition in ionized, He-like atoms), the design presented here maximizes the total photon flux by optimizing for intense, broadband Bremsstrahlung radiation. Three experiments were performed with identical targets, including a uranium x-ray source foil and a tungsten substrate with a narrow (25 μm wide) collimating slit to produce a quasi-1D x-ray source. Two experiments were performed using 12 beams from the NIF laser, each delivering approximately 46 kJ of laser energy but with different laser spatial profiles. This pair yielded similar temporal x-ray emission profiles, spatial resolution, and inferred hot electron temperature. A third experiment with only 6 beams delivering approximately 25 kJ produced a lower hot electron temperature and significantly lower x-ray flux, as well as poorer spatial resolution. The data suggest that laser pointing jitter may have affected the location and intensity of the emitting plasma, producing an emission volume that was not well centered behind the collimating slit and lower intensity than designed. However, the 12-beam design permits x-ray radiography through highly attenuating samples, where lower energy line-emission x-ray sources would be nearly completely attenuated.},
doi = {10.1063/1.5039379},
journal = {Review of Scientific Instruments},
number = 10,
volume = 89,
place = {United States},
year = {2018},
month = {10}
}

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This content will become publicly available on October 12, 2019
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