The Kelvin-Helmholtz instability in National Ignition Facility hohlraums as a source of gold-gas mixing

Journal Article · Sun May 15 04:00:00 EDT 2016 · Physics of Plasmas

DOI:https://doi.org/10.1063/1.4948468· OSTI ID:22600192

Vandenboomgaerde, M.; Bonnefille, M.; Gauthier, P. ^[1]

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1. CEA, DAM, DIF, F-91297 Arpajon (France)

Highly resolved radiation-hydrodynamics FCI2 simulations have been performed to model laser experiments on the National Ignition Facility. In these experiments, cylindrical gas-filled hohlraums with gold walls are driven by a 20 ns laser pulse. For the first time, simulations show the appearance of Kelvin-Helmholtz (KH) vortices at the interface between the expanding wall material and the gas fill. In this paper, we determine the mechanisms which generate this instability: the increase of the gas pressure around the expanding gold plasma leads to the aggregation of an over-dense gold layer simultaneously with shear flows. At the surface of this layer, all the conditions are met for a KH instability to grow. Later on, as the interface decelerates, the Rayleigh-Taylor instability also comes into play. A potential scenario for the generation of a mixing zone at the gold-gas interface due to the KH instability is presented. Our estimates of the Reynolds number and the plasma diffusion width at the interface support the possibility of such a mix. The key role of the first nanosecond of the laser pulse in the instability occurrence is also underlined.

• OSTI ID: 22600192
• Journal Information: Physics of Plasmas, Journal Name: Physics of Plasmas Journal Issue: 5 Vol. 23; ISSN PHPAEN; ISSN 1070-664X
• Country of Publication: United States
• Language: English

Related Subjects

70 PLASMA PHYSICS AND FUSION TECHNOLOGY
COMPUTERIZED SIMULATION
CYLINDRICAL CONFIGURATION
GOLD
HELMHOLTZ INSTABILITY
HYDRODYNAMIC MODEL
HYDRODYNAMICS
INTERFACES
LASERS
LAYERS
MIXING
PLASMA
PULSES
RAYLEIGH-TAYLOR INSTABILITY
REYNOLDS NUMBER
THERMONUCLEAR IGNITION
US NATIONAL IGNITION FACILITY
VORTICES