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Title: Spatially resolved X-ray emission measurements of the residual velocity during the stagnation phase of inertial confinement fusion implosion experiments

A technique for measuring residual motion during the stagnation phase of an indirectly driven inertial confinement experiment has been implemented. Our method infers a velocity from spatially and temporally resolved images of the X-ray emission from two orthogonal lines of sight. This work investigates the accuracy of recovering spatially resolved velocities from the X-ray emission data. A detailed analytical and numerical modeling of the X-ray emission measurement shows that the accuracy of this method increases as the displacement that results from a residual velocity increase. For the typical experimental configuration, signal-to-noise ratios, and duration of X-ray emission, it is estimated that the fractional error in the inferred velocity rises above 50% as the velocity of emission falls below 24 μm/ns. Furthermore, by inputting measured parameters into this model, error estimates of the residual velocity as inferred from the X-ray emission measurements are now able to be generated for experimental data. Details of this analysis are presented for an implosion experiment conducted with an unintentional radiation flux asymmetry. The analysis shows a bright localized region of emission that moves through the larger emitting volume at a relatively higher velocity towards the location of the imposed flux deficit. Our technique allows formore » the possibility of spatially resolving velocity flows within the so-called central hot spot of an implosion. This information would help to refine our interpretation of the thermal temperature inferred from the neutron time of flight detectors and the effect of localized hydrodynamic instabilities during the stagnation phase. Across several experiments, along a single line of sight, the average difference in magnitude and direction of the measured residual velocity as inferred from the X-ray and neutron time of flight detectors was found to be ~13 μm/ns and ~14°, respectively.« less
Authors:
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  1. Lawrence Livermore National Lab. (LLNL), Livermore, CA (United States)
  2. General Atomics, San Diego, CA (United States)
  3. Laboratory for Laser Energetics, Rochester, NY (United States)
  4. Los Alamos National Lab. (LANL), Los Alamos, NM (United States)
  5. Lawrence Livermore National Laboratory, P.O. Box 808, Livermore, California 94550, USA
Publication Date:
Report Number(s):
LLNL-JRNL-690145
Journal ID: ISSN 1070-664X; PHPAEN
Grant/Contract Number:
AC52-07NA27344
Type:
Accepted Manuscript
Journal Name:
Physics of Plasmas
Additional Journal Information:
Journal Volume: 23; Journal Issue: 7; Journal ID: ISSN 1070-664X
Publisher:
American Institute of Physics (AIP)
Research Org:
Lawrence Livermore National Lab. (LLNL), Livermore, CA (United States)
Sponsoring Org:
USDOE
Country of Publication:
United States
Language:
English
Subject:
70 PLASMA PHYSICS AND FUSION
OSTI Identifier:
1337001
Alternate Identifier(s):
OSTI ID: 1261222