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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

Abstract

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:
ORCiD logo [1];  [1];  [1];  [1];  [1];  [1];  [1]; ORCiD logo [1];  [1];  [1];  [1];  [1];  [1];  [1];  [1];  [1];  [2];  [1];  [3];  [1] more »;  [4];  [1]; ORCiD logo [1];  [5];  [5];  [5]; ORCiD logo [5];  [5];  [5];  [5];  [5] « less
  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:
Research Org.:
Lawrence Livermore National Lab. (LLNL), Livermore, CA (United States)
Sponsoring Org.:
USDOE
OSTI Identifier:
1337001
Report Number(s):
LLNL-JRNL-690145
Journal ID: ISSN 1070-664X; PHPAEN
Grant/Contract Number:
AC52-07NA27344
Resource Type:
Journal Article: 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)
Country of Publication:
United States
Language:
English
Subject:
70 PLASMA PHYSICS AND FUSION

Citation Formats

Ruby, J. J., Pak, A., Field, J. E., Ma, T., Spears, B. K., Benedetti, L. R., Bradley, D. K., Berzak Hopkins, L. F., Casey, D. T., Döppner, T., Eder, D., Fittinghoff, D., Grim, G., Hatarik, R., Hinkel, D. E., Izumi, N., Kilkenny, J. D., Khan, S. F., Knauer, J. P., Kritcher, A. L., Merrill, F. E., Moody, J. D., Nagel, S. R., Park, H. -S., Salmonson, J. D., Sayre, D. B., Callahan, D. A., Hsing, W. W., Hurricane, O. A., Patel, P. K., and Edwards, M. J.. Spatially resolved X-ray emission measurements of the residual velocity during the stagnation phase of inertial confinement fusion implosion experiments. United States: N. p., 2016. Web. doi:10.1063/1.4956468.
Ruby, J. J., Pak, A., Field, J. E., Ma, T., Spears, B. K., Benedetti, L. R., Bradley, D. K., Berzak Hopkins, L. F., Casey, D. T., Döppner, T., Eder, D., Fittinghoff, D., Grim, G., Hatarik, R., Hinkel, D. E., Izumi, N., Kilkenny, J. D., Khan, S. F., Knauer, J. P., Kritcher, A. L., Merrill, F. E., Moody, J. D., Nagel, S. R., Park, H. -S., Salmonson, J. D., Sayre, D. B., Callahan, D. A., Hsing, W. W., Hurricane, O. A., Patel, P. K., & Edwards, M. J.. Spatially resolved X-ray emission measurements of the residual velocity during the stagnation phase of inertial confinement fusion implosion experiments. United States. doi:10.1063/1.4956468.
Ruby, J. J., Pak, A., Field, J. E., Ma, T., Spears, B. K., Benedetti, L. R., Bradley, D. K., Berzak Hopkins, L. F., Casey, D. T., Döppner, T., Eder, D., Fittinghoff, D., Grim, G., Hatarik, R., Hinkel, D. E., Izumi, N., Kilkenny, J. D., Khan, S. F., Knauer, J. P., Kritcher, A. L., Merrill, F. E., Moody, J. D., Nagel, S. R., Park, H. -S., Salmonson, J. D., Sayre, D. B., Callahan, D. A., Hsing, W. W., Hurricane, O. A., Patel, P. K., and Edwards, M. J.. 2016. "Spatially resolved X-ray emission measurements of the residual velocity during the stagnation phase of inertial confinement fusion implosion experiments". United States. doi:10.1063/1.4956468. https://www.osti.gov/servlets/purl/1337001.
@article{osti_1337001,
title = {Spatially resolved X-ray emission measurements of the residual velocity during the stagnation phase of inertial confinement fusion implosion experiments},
author = {Ruby, J. J. and Pak, A. and Field, J. E. and Ma, T. and Spears, B. K. and Benedetti, L. R. and Bradley, D. K. and Berzak Hopkins, L. F. and Casey, D. T. and Döppner, T. and Eder, D. and Fittinghoff, D. and Grim, G. and Hatarik, R. and Hinkel, D. E. and Izumi, N. and Kilkenny, J. D. and Khan, S. F. and Knauer, J. P. and Kritcher, A. L. and Merrill, F. E. and Moody, J. D. and Nagel, S. R. and Park, H. -S. and Salmonson, J. D. and Sayre, D. B. and Callahan, D. A. and Hsing, W. W. and Hurricane, O. A. and Patel, P. K. and Edwards, M. J.},
abstractNote = {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 for 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.},
doi = {10.1063/1.4956468},
journal = {Physics of Plasmas},
number = 7,
volume = 23,
place = {United States},
year = 2016,
month = 7
}

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  • A technique for measuring residual motion during the stagnation phase of an indirectly driven inertial confinement experiment has been implemented. This 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 estimatedmore » that the fractional error in the inferred velocity rises above 50% as the velocity of emission falls below 24 μm/ns. 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. This technique allows for 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
  • A compact and simple multiframe x-ray imaging system was developed in order to monitor the implosion of spherical targets in inertial confinement fusion research. Time intervals between consecutive frames can be adjusted flexibly, and the maximum number of adjacent frames is 20 for an overall duration of 1.4 ns. Each frame is recorded with a temporal resolution of 83{plus minus}20 ps, a spatial resolution of 10 lp/mm at a modulation transfer function of 20%, and an intensity dynamic range of 10{sup 3}. A proximity focused image intensifier with two microchannel plates allows to obtain a gain of 10{sup 5}. Measuredmore » temporal response and gain characteristics could be reproduced by a simple Monte Carlo calculation.« less
  • A set of laser implosion experiments were conducted at the OMEGA laser at the Univ. of Rochester, Laboratory for Laser Energetics (LLE) to study the effect of He concentration in DT-filled target shells on fusion yield in ICF implosions.. Eleven laser fusion shells consisting of 1100-{mu}m diameter, hollow, fused silica spheres with 4.6 to 4.7-{mu}m-thick walls were loaded with 520 kPa of deuterium-tritium (DT) and then with {sup 3}He (101.3 or 520 kPa). The {sup 3}He permeabilities of the shells were determined by measuring the pressure rate of rise into a system with known volume. A mathematical method was developedmore » that relied on the experimental fill pressure and time, and the rate of rise data to solve differential equations using MathCAD to simultaneously calculate {sup 3}He permeability and initial {sup 3}He partial pressure inside the shell. Because of the high permeation rate for {sup 3}He out of the shells compared to that for DT gas, shells had to be recharged with {sup 3}He immediately before being laser imploded or 'shot' at LLE. The {sup 3}He partial pressure in each individual shell at shot time was calculated from the measured {sup 3}He permeability. Two different partial pressures of {sup 3}He inside the shell were shown to reduce neutron and gamma yields during implosion. (authors)« less
  • We discuss the processing of data recorded with multimonochromatic x-ray imagers (MMI) in inertial confinement fusion experiments. The MMI records hundreds of gated, spectrally resolved images that can be used to unravel the spatial structure of the implosion core. In particular, we present a new method to determine the centers in all the array of images, a better reconstruction technique of narrowband implosion core images, two algorithms to determine the shape and size of the implosion core volume based on reconstructed broadband images recorded along three-quasiorthogonal lines of sight, and the removal of artifacts from the space-integrated spectra.