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

Abstract

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 (N_e) = 8.5 × 10²⁴ ± 2.5 × 10²⁴ cm^–3, and average areal density <ρR> = 86 ±more » 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.« less

Authors:

Johns, H. M. ^[1]; Mancini, R. C. ^[2]; Nagayama, T. ^[2]; Mayes, D. C. ^[2]; Tommasini, R. ^[3]; Smalyuk, V. A. ^[3]; Regan, S. P. ^[4]; Delettrez, J. A.  ^[4]

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+ Show Author Affiliations

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

Publication Date:

Mon Jan 25 00:00:00 EST 2016

Research Org.:

Los Alamos National Laboratory (LANL), Los Alamos, NM (United States); Lawrence Livermore National Lab., Livermore, CA (United States)

Sponsoring Org.:

USDOE

OSTI Identifier:

1240381

Alternate Identifier(s):

OSTI ID: 1235975; OSTI ID: 1281660

Report Number(s):

LA-UR-14-29462; LLNL-JRNL-696064
Journal ID: ISSN 1070-664X; PHPAEN

Grant/Contract Number:  

NA0000859; NA0002267; AC52-06NA25396; AC52-07NA27344

Resource Type:

Accepted Manuscript

Journal Name:

Physics of Plasmas

Additional Journal Information:

Journal Volume: 23; Journal Issue: 1; Journal ID: ISSN 1070-664X

Publisher:

American Institute of Physics (AIP)

Country of Publication:

United States

Language:

English

Subject:

70 PLASMA PHYSICS AND FUSION TECHNOLOGY; direct-drive ICF; mix width; hydrodynamic instability; shell areal density modulations; x-ray absorption spectroscopy; shell breakup; shell stability; 70 PLASMA PHYSICS AND FUSION; 42 ENGINEERING; direct-drive; OMEGA; shell-fuel mix width; shell pL modulations; Ti-doped shells; shell breakup and stability