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Title: In-flight observations of low-mode ρR asymmetries in NIF implosions

Abstract

Charged-particle spectroscopy is used to assess implosion symmetry in ignition-scale indirect-drive implosions for the first time. Surrogate D{sup 3}He gas-filled implosions at the National Ignition Facility produce energetic protons via D+{sup 3}He fusion that are used to measure the implosion areal density (ρR) at the shock-bang time. By using protons produced several hundred ps before the main compression bang, the implosion is diagnosed in-flight at a convergence ratio of 3–5 just prior to peak velocity. This isolates acceleration-phase asymmetry growth. For many surrogate implosions, proton spectrometers placed at the north pole and equator reveal significant asymmetries with amplitudes routinely ≳10%, which are interpreted as ℓ=2 Legendre modes. With significant expected growth by stagnation, it is likely that these asymmetries would degrade the final implosion performance. X-ray self-emission images at stagnation show asymmetries that are positively correlated with the observed in-flight asymmetries and comparable in magnitude, contradicting growth models; this suggests that the hot-spot shape does not reflect the stagnated shell shape or that significant residual kinetic energy exists at stagnation. More prolate implosions are observed when the laser drive is sustained (“no-coast”), implying a significant time-dependent asymmetry in peak drive.

Authors:
; ; ; ; ; ; ; ; ; ;  [1]; ; ; ; ; ; ; ; ;  [2] more »; « less
  1. Plasma Science and Fusion Center, Massachusetts Institute of Technology, Cambridge, Massachusetts 02139 (United States)
  2. Lawrence Livermore National Laboratory, Livermore, California 94550 (United States)
Publication Date:
OSTI Identifier:
22410397
Resource Type:
Journal Article
Journal Name:
Physics of Plasmas
Additional Journal Information:
Journal Volume: 22; Journal Issue: 5; Other Information: (c) 2015 AIP Publishing LLC; Country of input: International Atomic Energy Agency (IAEA); Journal ID: ISSN 1070-664X
Country of Publication:
United States
Language:
English
Subject:
70 PLASMA PHYSICS AND FUSION TECHNOLOGY; ACCELERATION; ASYMMETRY; CHARGED PARTICLES; CONVERGENCE; DENSITY; DEUTERIUM; HEAVY ION FUSION REACTIONS; HELIUM 3; HOT SPOTS; IMAGES; IMPLOSIONS; KINETIC ENERGY; PLASMA DIAGNOSTICS; PROTON SPECTROMETERS; PROTONS; SPECTROSCOPY; STAGNATION; TIME DEPENDENCE; US NATIONAL IGNITION FACILITY; X RADIATION

Citation Formats

Zylstra, A. B., E-mail: zylstra@mit.edu, Frenje, J. A., Séguin, F. H., Rosenberg, M. J., Rinderknecht, H. G., Gatu Johnson, M., Li, C. K., Manuel, M. J.-E., Petrasso, R. D., Sinenian, N., Sio, H. W., Rygg, J. R., Kritcher, A., Hicks, D. G., Friedrich, S., Bionta, R., Meezan, N. B., Atherton, J., Barrios, M., Bell, P., and and others. In-flight observations of low-mode ρR asymmetries in NIF implosions. United States: N. p., 2015. Web. doi:10.1063/1.4918355.
Zylstra, A. B., E-mail: zylstra@mit.edu, Frenje, J. A., Séguin, F. H., Rosenberg, M. J., Rinderknecht, H. G., Gatu Johnson, M., Li, C. K., Manuel, M. J.-E., Petrasso, R. D., Sinenian, N., Sio, H. W., Rygg, J. R., Kritcher, A., Hicks, D. G., Friedrich, S., Bionta, R., Meezan, N. B., Atherton, J., Barrios, M., Bell, P., & and others. In-flight observations of low-mode ρR asymmetries in NIF implosions. United States. doi:10.1063/1.4918355.
Zylstra, A. B., E-mail: zylstra@mit.edu, Frenje, J. A., Séguin, F. H., Rosenberg, M. J., Rinderknecht, H. G., Gatu Johnson, M., Li, C. K., Manuel, M. J.-E., Petrasso, R. D., Sinenian, N., Sio, H. W., Rygg, J. R., Kritcher, A., Hicks, D. G., Friedrich, S., Bionta, R., Meezan, N. B., Atherton, J., Barrios, M., Bell, P., and and others. Fri . "In-flight observations of low-mode ρR asymmetries in NIF implosions". United States. doi:10.1063/1.4918355.
@article{osti_22410397,
title = {In-flight observations of low-mode ρR asymmetries in NIF implosions},
author = {Zylstra, A. B., E-mail: zylstra@mit.edu and Frenje, J. A. and Séguin, F. H. and Rosenberg, M. J. and Rinderknecht, H. G. and Gatu Johnson, M. and Li, C. K. and Manuel, M. J.-E. and Petrasso, R. D. and Sinenian, N. and Sio, H. W. and Rygg, J. R. and Kritcher, A. and Hicks, D. G. and Friedrich, S. and Bionta, R. and Meezan, N. B. and Atherton, J. and Barrios, M. and Bell, P. and and others},
abstractNote = {Charged-particle spectroscopy is used to assess implosion symmetry in ignition-scale indirect-drive implosions for the first time. Surrogate D{sup 3}He gas-filled implosions at the National Ignition Facility produce energetic protons via D+{sup 3}He fusion that are used to measure the implosion areal density (ρR) at the shock-bang time. By using protons produced several hundred ps before the main compression bang, the implosion is diagnosed in-flight at a convergence ratio of 3–5 just prior to peak velocity. This isolates acceleration-phase asymmetry growth. For many surrogate implosions, proton spectrometers placed at the north pole and equator reveal significant asymmetries with amplitudes routinely ≳10%, which are interpreted as ℓ=2 Legendre modes. With significant expected growth by stagnation, it is likely that these asymmetries would degrade the final implosion performance. X-ray self-emission images at stagnation show asymmetries that are positively correlated with the observed in-flight asymmetries and comparable in magnitude, contradicting growth models; this suggests that the hot-spot shape does not reflect the stagnated shell shape or that significant residual kinetic energy exists at stagnation. More prolate implosions are observed when the laser drive is sustained (“no-coast”), implying a significant time-dependent asymmetry in peak drive.},
doi = {10.1063/1.4918355},
journal = {Physics of Plasmas},
issn = {1070-664X},
number = 5,
volume = 22,
place = {United States},
year = {2015},
month = {5}
}