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Title: X-ray streaked refraction enhanced radiography for inferring inflight density gradients in ICF capsule implosions

In the quest for reaching ignition of deuterium-tritium (DT) fuel capsule implosions, experiments on the National Ignition Facility (NIF) have shown lower final fuel areal densities than simulated. Possible explanations for reduced compression are higher preheat that can increase the ablator-DT ice density jump and induce mix at that interface or reverberating shocks. We are hence developing x-ray Refraction Enhanced Radiography (RER) to infer the inflight density profiles in layered fuel capsule implosions. We use a 5 μm slit backlit by a Ni 7.8 keV He-α NIF laser driven x-ray source positioned at 20 mm from the capsule to cast refracted images of the inflight capsule onto a streak camera in a high magnification (M ~ 60×) setup. Our first experiments have validated our setup that recorded a streaked x-ray fringe pattern from an undriven high density carbon (HDC) capsule consistent with ray tracing calculations at the required ~6 μm and 25 ps resolution. Streaked RER was then applied to inflight layered HDC capsule implosions using a hydrogen-tritium fuel mix rather than DT to reduce neutron yields and associated backgrounds. The first RER of an imploding capsule revealed strong features associated with the ablation front and ice-ablator interface that aremore » not visible in standard absorption radiographs.« less
Authors:
 [1] ; ORCiD logo [1] ; ORCiD logo [1] ;  [1] ;  [1] ;  [1] ; ORCiD logo [1] ; ORCiD logo [1] ;  [1] ; ORCiD logo [1] ;  [2]
  1. Lawrence Livermore National Lab. (LLNL), Livermore, CA (United States)
  2. Nevada National Security Site, Livermore, CA (United States)
Publication Date:
Report Number(s):
LLNL-JRNL-750878
Journal ID: ISSN 0034-6748; 936350
Grant/Contract Number:
AC52-07NA27344
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)
Research Org:
Lawrence Livermore National Lab. (LLNL), Livermore, CA (United States)
Sponsoring Org:
USDOE National Nuclear Security Administration (NNSA)
Country of Publication:
United States
Language:
English
Subject:
70 PLASMA PHYSICS AND FUSION TECHNOLOGY; Lasers
OSTI Identifier:
1477148
Alternate Identifier(s):
OSTI ID: 1471145

Dewald, E. L., Landen, O. L., Masse, L., Ho, D., Ping, Y., Thorn, D., Izumi, N., Berzak Hopkins, L., Kroll, J., Nikroo, A., and Koch, J. A.. X-ray streaked refraction enhanced radiography for inferring inflight density gradients in ICF capsule implosions. United States: N. p., Web. doi:10.1063/1.5039346.
Dewald, E. L., Landen, O. L., Masse, L., Ho, D., Ping, Y., Thorn, D., Izumi, N., Berzak Hopkins, L., Kroll, J., Nikroo, A., & Koch, J. A.. X-ray streaked refraction enhanced radiography for inferring inflight density gradients in ICF capsule implosions. United States. doi:10.1063/1.5039346.
Dewald, E. L., Landen, O. L., Masse, L., Ho, D., Ping, Y., Thorn, D., Izumi, N., Berzak Hopkins, L., Kroll, J., Nikroo, A., and Koch, J. A.. 2018. "X-ray streaked refraction enhanced radiography for inferring inflight density gradients in ICF capsule implosions". United States. doi:10.1063/1.5039346.
@article{osti_1477148,
title = {X-ray streaked refraction enhanced radiography for inferring inflight density gradients in ICF capsule implosions},
author = {Dewald, E. L. and Landen, O. L. and Masse, L. and Ho, D. and Ping, Y. and Thorn, D. and Izumi, N. and Berzak Hopkins, L. and Kroll, J. and Nikroo, A. and Koch, J. A.},
abstractNote = {In the quest for reaching ignition of deuterium-tritium (DT) fuel capsule implosions, experiments on the National Ignition Facility (NIF) have shown lower final fuel areal densities than simulated. Possible explanations for reduced compression are higher preheat that can increase the ablator-DT ice density jump and induce mix at that interface or reverberating shocks. We are hence developing x-ray Refraction Enhanced Radiography (RER) to infer the inflight density profiles in layered fuel capsule implosions. We use a 5 μm slit backlit by a Ni 7.8 keV He-α NIF laser driven x-ray source positioned at 20 mm from the capsule to cast refracted images of the inflight capsule onto a streak camera in a high magnification (M ~ 60×) setup. Our first experiments have validated our setup that recorded a streaked x-ray fringe pattern from an undriven high density carbon (HDC) capsule consistent with ray tracing calculations at the required ~6 μm and 25 ps resolution. Streaked RER was then applied to inflight layered HDC capsule implosions using a hydrogen-tritium fuel mix rather than DT to reduce neutron yields and associated backgrounds. The first RER of an imploding capsule revealed strong features associated with the ablation front and ice-ablator interface that are not visible in standard absorption radiographs.},
doi = {10.1063/1.5039346},
journal = {Review of Scientific Instruments},
number = 10,
volume = 89,
place = {United States},
year = {2018},
month = {10}
}

Works referenced in this record:

Refraction-enhanced x-ray radiography for inertial confinement fusion and laser-produced plasma applications
journal, June 2009
  • Koch, Jeffrey A.; Landen, Otto L.; Kozioziemski, Bernard J.
  • Journal of Applied Physics, Vol. 105, Issue 11, Article No. 113112
  • DOI: 10.1063/1.3133092