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Title: Shell stability and conditions analyzed using a new method of extracting shell areal density maps from spectrally resolved images of direct-drive inertial confinement fusion implosions

Journal Article · · Physics of Plasmas
DOI:https://doi.org/10.1063/1.4940672· OSTI ID:1240381
 [1];  [2];  [2];  [2];  [3];  [3];  [4]; ORCiD logo [4]
  1. Univ. of Nevada, Reno, NV (United States). Physics Department; Los Alamos National Lab. (LANL), Los Alamos, NM (United States)
  2. Univ. of Nevada, Reno, NV (United States). Physics Department
  3. Lawrence Livermore National Lab. (LLNL), Livermore, CA (United States)
  4. Univ. of Rochester, NY (United States). Lab. for Laser Energetics

In warm target direct-drive inertial confinement fusion implosion experiments performed at the OMEGA laser facility, plastic micro-balloons doped with a titanium tracer layer in the shell and filled with deuterium gas were imploded using a low-adiabat shaped laser pulse. Continuum radiation emitted in the core is transmitted through the tracer layer and the resulting spectrum recorded with a gated multi-monochromatic x-ray imager (MMI). Titanium K-shell line absorption spectra observed in the data are due to transitions in L-shell titanium ions driven by the backlighting continuum. The MMI data consist of an array of spectrally resolved images of the implosion. These 2-D space-resolved titanium spectral features constrain the plasma conditions and areal density of the titanium doped region of the shell. The MMI data were processed to obtain narrow-band images and space resolved spectra of titanium spectral features. Shell areal density maps, ρL(x,y), extracted using a new method using both narrow-band images and space resolved spectra are confirmed to be consistent within uncertainties. We report plasma conditions in the titanium-doped region of electron temperature (Te) = 400 ± 28 eV, electron number density (Ne) = 8.5 × 1024 ± 2.5 × 1024 cm–3, and average areal density <ρR> = 86 ± 7 mg/cm2. Fourier analysis of areal density maps reveals shell modulations caused by hydrodynamic instability growth near the fuel-shell interface in the deceleration phase. We observe significant structure in modes l = 2–9, dominated by l = 2. We extract a target breakup fraction of 7.1 ± 1.5% from our Fourier analysis. Furthermore, a new method for estimating mix width is evaluated against existing literature and our target breakup fraction. We estimate a mix width of 10.5 ±1 μm.

Research Organization:
Los Alamos National Laboratory (LANL), Los Alamos, NM (United States); Lawrence Livermore National Lab., Livermore, CA (United States)
Sponsoring Organization:
USDOE
Grant/Contract Number:
NA0000859; NA0002267; AC52-06NA25396; AC52-07NA27344
OSTI ID:
1240381
Alternate ID(s):
OSTI ID: 1235975; OSTI ID: 1281660
Report Number(s):
LA-UR-14-29462; LLNL-JRNL-696064; PHPAEN
Journal Information:
Physics of Plasmas, Vol. 23, Issue 1; ISSN 1070-664X
Publisher:
American Institute of Physics (AIP)Copyright Statement
Country of Publication:
United States
Language:
English
Citation Metrics:
Cited by: 7 works
Citation information provided by
Web of Science

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Impact of 3D effects on the characteristics of a multi-monochromatic x-ray imager journal January 2019