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Title: Observation of early shell-dopant mix in OMEGA direct-drive implosions and comparisons with radiation-hydrodynamic simulations

Abstract

Temporally, spatially, and spectrally resolved x-ray image data from direct-drive implosions on OMEGA were interpreted with the aid of radiation-hydrodynamic simulations. Neither clean calculations nor those using a turbulent mix model can explain fully the observed migration of shell-dopant material (titanium) into the core. Shell-dopant migration was observed via time-dependent, spatially integrated spectra, and spatially and spectrally resolved x-ray images of capsule implosions and resultant dopant emissions. The titanium emission was centrally peaked in narrowband x-ray images. In post-processed clean simulations, the peak titanium emission forms in a ring in self-emission images as the capsule implodes. Post-processed simulations with mix reproduce trends in time-dependent, spatially integrated spectra, as well having centrally peaked Ti emission in synthetic multiple monochromatic imager. However, mix simulations still do not transport Ti to the core as is observed in the experiment. This suggests that phenomena in addition to the turbulent mix must be responsible for the transport of Ti. Simple diffusion estimates are unable to explain the early Ti mix into the core. Mechanisms suggested for further study are capsule surface roughness, illumination non-uniformity, and shock entrainment.

Authors:
; ; ; ; ; ; ; ; ; ; ;  [1]; ; ; ; ;  [2]
  1. Los Alamos National Laboratory, Los Alamos, New Mexico 87545 (United States)
  2. Physics Department, University of Nevada, Reno, Nevada 89557 (United States)
Publication Date:
OSTI Identifier:
22300129
Resource Type:
Journal Article
Resource Relation:
Journal Name: Physics of Plasmas; Journal Volume: 21; Journal Issue: 5; Other Information: (c) 2014 AIP Publishing LLC; Country of input: International Atomic Energy Agency (IAEA)
Country of Publication:
United States
Language:
English
Subject:
70 PLASMA PHYSICS AND FUSION TECHNOLOGY; CAPSULES; COMPARATIVE EVALUATIONS; EMISSION; IMAGES; IMPLOSIONS; SIMULATION; TIME DEPENDENCE; TITANIUM; X RADIATION; X-RAY SPECTRA

Citation Formats

Baumgaertel, J. A., Bradley, P. A., Hsu, S. C., Cobble, J. A., Hakel, P., Tregillis, I. L., Krasheninnikova, N. S., Murphy, T. J., Schmitt, M. J., Shah, R. C., Obrey, K. D., Batha, S., Johns, H., Joshi, T., Mayes, D., Mancini, R. C., and Nagayama, T. Observation of early shell-dopant mix in OMEGA direct-drive implosions and comparisons with radiation-hydrodynamic simulations. United States: N. p., 2014. Web. doi:10.1063/1.4881463.
Baumgaertel, J. A., Bradley, P. A., Hsu, S. C., Cobble, J. A., Hakel, P., Tregillis, I. L., Krasheninnikova, N. S., Murphy, T. J., Schmitt, M. J., Shah, R. C., Obrey, K. D., Batha, S., Johns, H., Joshi, T., Mayes, D., Mancini, R. C., & Nagayama, T. Observation of early shell-dopant mix in OMEGA direct-drive implosions and comparisons with radiation-hydrodynamic simulations. United States. doi:10.1063/1.4881463.
Baumgaertel, J. A., Bradley, P. A., Hsu, S. C., Cobble, J. A., Hakel, P., Tregillis, I. L., Krasheninnikova, N. S., Murphy, T. J., Schmitt, M. J., Shah, R. C., Obrey, K. D., Batha, S., Johns, H., Joshi, T., Mayes, D., Mancini, R. C., and Nagayama, T. Thu . "Observation of early shell-dopant mix in OMEGA direct-drive implosions and comparisons with radiation-hydrodynamic simulations". United States. doi:10.1063/1.4881463.
@article{osti_22300129,
title = {Observation of early shell-dopant mix in OMEGA direct-drive implosions and comparisons with radiation-hydrodynamic simulations},
author = {Baumgaertel, J. A. and Bradley, P. A. and Hsu, S. C. and Cobble, J. A. and Hakel, P. and Tregillis, I. L. and Krasheninnikova, N. S. and Murphy, T. J. and Schmitt, M. J. and Shah, R. C. and Obrey, K. D. and Batha, S. and Johns, H. and Joshi, T. and Mayes, D. and Mancini, R. C. and Nagayama, T.},
abstractNote = {Temporally, spatially, and spectrally resolved x-ray image data from direct-drive implosions on OMEGA were interpreted with the aid of radiation-hydrodynamic simulations. Neither clean calculations nor those using a turbulent mix model can explain fully the observed migration of shell-dopant material (titanium) into the core. Shell-dopant migration was observed via time-dependent, spatially integrated spectra, and spatially and spectrally resolved x-ray images of capsule implosions and resultant dopant emissions. The titanium emission was centrally peaked in narrowband x-ray images. In post-processed clean simulations, the peak titanium emission forms in a ring in self-emission images as the capsule implodes. Post-processed simulations with mix reproduce trends in time-dependent, spatially integrated spectra, as well having centrally peaked Ti emission in synthetic multiple monochromatic imager. However, mix simulations still do not transport Ti to the core as is observed in the experiment. This suggests that phenomena in addition to the turbulent mix must be responsible for the transport of Ti. Simple diffusion estimates are unable to explain the early Ti mix into the core. Mechanisms suggested for further study are capsule surface roughness, illumination non-uniformity, and shock entrainment.},
doi = {10.1063/1.4881463},
journal = {Physics of Plasmas},
number = 5,
volume = 21,
place = {United States},
year = {Thu May 15 00:00:00 EDT 2014},
month = {Thu May 15 00:00:00 EDT 2014}
}
  • Multidimensional hydrodynamic properties of high-adiabat direct-drive plastic-shell implosions on the OMEGA laser system are investigated using the multidimensional hydrodynamic code, DRACO. Multimode simulations including the effects of nonuniform illumination and target roughness indicate that shell stability during the acceleration phase plays a critical role in determining target performance.
  • Multidimensional hydrodynamic properties of high-adiabat direct-drive plastic-shell implosions on the OMEGA laser system [T. R. Boehly et al., Opt. Commun. 133, 495 (1997)] are investigated using the multidimensional hydrodynamic code, DRACO. Multimode simulations including the effects of nonuniform illumination and target roughness indicate that shell stability during the acceleration phase plays a critical role in determining target performance. For thick shells that remain integral during the acceleration phase, target yields are significantly reduced by the combination of the long-wavelength ({ell} < 10) modes due to surface roughness and beam imbalance and the intermediate modes (20 {le} {ell} {le} 50) duemore » to single-beam nonuniformities. The neutron-production rate for these thick shells truncates relative to one-dimensional (1-D) predictions. The yield degradation in the thin shells is mainly due to shell breakup at short wavelengths ({lambda} {approx} {Delta}, where {Delta} is the in-flight shell thickness). The neutron-rate curves for the thinner shells have significantly lower amplitudes and a fall-off that is less steep than 1-D rates. DRACO simulation results are consistent with experimental observations.« less
  • Multidimensional hydrodynamic properties of high-adiabat direct-drive plastic-shell implosions on the OMEGA laser system [T. R. Boehly et al., Opt. Commun. 133, 495 (1997)] are investigated using the multidimensional hydrodynamic code, DRACO [D. Keller et al., Bull. Am. Phys. Soc. 44, 37 (1999)]. Multimode simulations including the effects of nonuniform illumination and target roughness indicate that shell stability during the acceleration phase plays a critical role in determining target performance. For thick shells that remain integral during the acceleration phase, target yields are significantly reduced by the combination of the long-wavelength (l<10) modes due to surface roughness and beam imbalance andmore » the intermediate modes (20{<=}l{<=}50) due to single-beam nonuniformities. The neutron-production rate for these thick shells truncates relative to one-dimensional (1D) predictions. The yield degradation in the thin shells is mainly due to shell breakup at short wavelengths ({lambda}{approx}{delta}, where {delta} is the in-flight shell thickness). The neutron-rate curves for the thinner shells have significantly lower amplitudes and a fall-off that is less steep than 1D rates. DRACO simulation results are consistent with experimental observations.« less
  • OAK B204 The evolution of shell modulations was measured in targets with titanium-doped layers using differential imaging [B. Yaakobi et al., Phys. Plasmas 7, 3727 (2000)] near peak compression of direct-drive spherical implosions. Inner-shell modulations grow throughout the deceleration phase of the implosion due to the Rayleigh-Taylor instability with relative modulation levels of {approx}20% at peak neutron production and {approx}50% at peak compression ({approx}100 ps later) in targets with 1-mm-diam, 20-mm-thick shells filled with 4 atm of D3He gas. In addition, the shell modulations grow up to about 1.5 times due to Bell-Plesset convergent effects during the same period. Atmore » peak compression the inner part of the shell has a higher modulation level than other parts of the shell.« less
  • Direct-drive, plastic-shells imploded on the OMEGA laser system with a 1-ns square pulse are simulated using the multidimensional hydrodynamic code DRACO.