Areal density evolution of isolated surface perturbations at the onset of x-ray ablation Richtmyer-Meshkov growth

Journal Article · Thu Sep 15 00:00:00 EDT 2011 · Physics of Plasmas

DOI:https://doi.org/10.1063/1.3632083· OSTI ID:22043504

Loomis, E N; Batha, S H ^[1]; Braun, D; Sorce, C; Landen, O L ^[2]

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1. Los Alamos National Laboratory, Los Alamos, New Mexico 87544 (United States)
2. Lawrence Livermore National Laboratory, Livermore, California 95281 (United States)

Isolated defects on inertial confinement fusion ignition capsules are a concern as defects taller than a few hundred nanometers are calculated to form jets of high-Z material, which enter the main fuel. If this mixing of high-Z material is not controlled, a serious degradation in thermonuclear burn can occur. A path towards controlling the growth of defects on the outer surface of plastic capsules is currently under development, but requires accurate predictions of defect evolution driven by the early time ablative Richtmyer-Meshkov (RM) effect. The chief uncertainty is the Equation of State (EOS) for polystyrene and its effect on ablative RM. We report on measurements of the growth of isolated defects made at the onset of ablative RM oscillations driven by x-ray ablation to differentiate between EOS models used in design calculations. Experiments at the OMEGA laser [T. R. Boehly et al., Opt. Commun. 133, 495 (1997)] used on-axis area backlighting radiography and x-ray framing cameras to determine bump areal densities at discrete times. Bumps 12 and 14 {mu}m tall and 33 {mu}m FWHM were found to grow to 2 x their initial areal density by 3 ns after the start of the drive laser pulse. Shock speed measurements established target conditions resulting from the ablation process. The tabular LEOS 5310 [D. Young and E. Corey, J. Appl. Phys. 78, 3748 (1995)] model shows good agreement with measured shock speeds and bump growth whereas the QEOS model [R. More et al., Phys. Fluids 31, 3059 (1988)] over predicts shock speed and under predicts bump growth by 6x. Differences in ablative RM behavior were also found for x-ray ablation compared to laser ablation, which result in an overestimation (or non-existence) of oscillation frequency for x-ray ablation as predicted by theory.

• OSTI ID: 22043504
• Journal Information: Physics of Plasmas, Vol. 18, Issue 9; Other Information: (c) 2011 American Institute of Physics; Country of input: International Atomic Energy Agency (IAEA); ISSN 1070-664X
• Country of Publication: United States
• Language: English

Related Subjects

70 PLASMA PHYSICS AND FUSION TECHNOLOGY
ABLATION
DENSITY
DESIGN
DISTURBANCES
EQUATIONS OF STATE
INERTIAL CONFINEMENT
LASER RADIATION
MIXING
OSCILLATIONS
PERTURBATION THEORY
PLASMA DENSITY
PLASMA DIAGNOSTICS
PLASMA IMPURITIES
PLASMA JETS
PLASMA WAVES
POLYSTYRENE
PULSES
SURFACES
X RADIATION
X-RAY SOURCES