A model of laser imprinting

Goncharov, V. N.; Skupsky, S.; Boehly, T. R.; Knauer, J. P.; McKenty, P. W.; Smalyuk, V. A.; Town, R. P. J.; Gotchev, O. V.; Betti, R.; Meyerhofer, D. D.

doi:10.1063/1.874028

Cited by 83 publications

(66 citation statements)

References 32 publications

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“…This is called laser imprint, which also causes a RTI seed in ICF implosion (Emery et al 1991;Ishizaki & Nishihara 1997Taylor et al 1997;Nishihara et al 1998;Matsui et al 1999;Goncharov et al 2000;Velikovich et al 2000). A rippled shock wave and ablation surface deformation caused by non-uniform laser irradiation on a smooth target were also evaluated with the deflagration model (Ishizaki & Nishihara 1997).…”

Section: (E) Rm-like Instabilities and Ablative Rmimentioning

confidence: 99%

“…Another stabilization mechanism in ablative RMI, called dynamic overpressure, is discussed in Goncharov (1999) and Goncharov et al (2000), in which the sharp-boundary model (SBM) was used instead of the deflagration model. The SBM was originally developed to study ablative RTI (Piriz et al 1997).…”

Section: (E) Rm-like Instabilities and Ablative Rmimentioning

confidence: 99%

“…The increased temperature gradient enhances local heat flux and then increases the rate of mass ablation, producing the dynamic pressure that pushes the front back. This results in an oscillation of the ablation surface ripple, and the peak value of the ripple amplitude is determined from the overpressure (Goncharov 1999;Goncharov et al 2000).…”

Section: (E) Rm-like Instabilities and Ablative Rmimentioning

confidence: 99%

“…The interaction between the rippled shock front and the ablation surface through sound waves may induce RM-like instability. It is important to study such growth of RM-like instabilities because they determine the seed of the RT instability that develops during the acceleration phase in ICF (Emery et al 1991;Desselberger et al 1995;Endo et al 1995;Azechi et al 1997;Ishizaki & Nishihara 1997Taylor et al 1997;Nishihara et al 1998;Goncharov 1999;Matsui et al 1999;Goncharov et al 2000;Velikovich et al 2000). A simple analytical model was developed to study propagation of a rippled shock associated with the initial surface roughness of a target in Ishizaki & Nishihara (1997.…”

Section: (E) Rm-like Instabilities and Ablative Rmimentioning

confidence: 99%

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Richtmyer–Meshkov instability: theory of linear and nonlinear evolution

Nishihara

Wouchuk

Matsuoka

et al. 2010

Phil. Trans. R. Soc. A.

129

128

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A theoretical framework to study linear and nonlinear Richtmyer-Meshkov instability (RMI) is presented. This instability typically develops when an incident shock crosses a corrugated material interface separating two fluids with different thermodynamic properties. Because the contact surface is rippled, the transmitted and reflected wavefronts are also corrugated, and some circulation is generated at the material boundary. The velocity circulation is progressively modified by the sound wave field radiated by the wavefronts, and ripple growth at the contact surface reaches a constant asymptotic normal velocity when the shocks/rarefactions are distant enough. The instability growth is driven by two effects: an initial deposition of velocity circulation at the material interface by the corrugated shock fronts and its subsequent variation in time due to the sonic field of pressure perturbations radiated by the deformed shocks. First, an exact analytical model to determine the asymptotic linear growth rate is presented and its dependence on the governing parameters is briefly discussed. Instabilities referred to as RM-like, driven by localized non-uniform vorticity, also exist; they are either initially deposited or supplied by external sources. Ablative RMI and its stabilization mechanisms are discussed as an example. When the ripple amplitude increases and becomes comparable to the perturbation wavelength, the instability enters the nonlinear phase and the perturbation velocity starts to decrease. An analytical model to describe this second stage of instability evolution is presented within the limit of incompressible and irrotational fluids, based on the dynamics of the contact surface circulation. RMI in solids and liquids is also presented via molecular dynamics simulations for planar and cylindrical geometries, where we show the generation of vorticity even in viscid materials.

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Section: (E) Rm-like Instabilities and Ablative Rmimentioning

confidence: 99%

Section: (E) Rm-like Instabilities and Ablative Rmimentioning

confidence: 99%

Section: (E) Rm-like Instabilities and Ablative Rmimentioning

confidence: 99%

Section: (E) Rm-like Instabilities and Ablative Rmimentioning

confidence: 99%

See 2 more Smart Citations

Richtmyer–Meshkov instability: theory of linear and nonlinear evolution

Nishihara

Wouchuk

Matsuoka

et al. 2010

Phil. Trans. R. Soc. A.

129

128

View full text Add to dashboard Cite

show abstract

“…Simulations have shown that laser imprint occurs primarily during the low intensity foot pulse. 7,8 A long scale buffering plasma forms during the higher intensity main pulse that smoothes the effects of laser illumination nonuniformity. The relatively cold (50-100eV) plasma that forms during the foot pulse does not have sufficiently good electron thermal conductivity between the target and the laser absorption region to allow such long scale plasmas to form.…”

Section: Introductionmentioning

confidence: 99%

Effects of thin high-Z layers on the hydrodynamics of laser-accelerated plastic targets

et al. 2002

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We present experimental results and simulations that study the effects of thin metallic layers with high atomic number (high-Z) on the hydrodynamics of laser accelerated plastic targets. These experiments employ a laser pulse with a low-intensity foot that rises into a high-intensity main pulse. This pulse shape simulates the generic Report Documentation PageForm Public reporting burden for the collection of information is estimated to average 1 hour per response, including the time for reviewing instructions, searching existing data sources, gathering and maintaining the data needed, and completing and reviewing the collection of information. Send comments regarding this burden estimate or any other aspect of this collection of information, including suggestions for reducing this burden, to Washington Headquarters Services, Directorate for Information Operations and Reports, 1215 Jefferson Davis Highway, Suite 1204, Arlington VA 22202-4302. Respondents should be aware that notwithstanding any other provision of law, no person shall be subject to a penalty for failing to comply with a collection of information if it does not display a currently valid OMB control number. We present experimental results and simulations that study the effects of thin metallic layers with high atomic number (high-Z) on the hydrodynamics of laser accelerated plastic targets. These experiments employ a laser pulse with a low-intensity foot that rises into a high-intensity main pulse. This pulse shape simulates the generic shape needed for high-gain fusion implosions. Imprint of laser nonuniformity during start up of the low intensity foot is a well-known seed for hydrodynamic instability. We observe large reductions in hydrodynamic instability seeded by laser imprint when certain minimum thickness gold or palladium layers are applied to the laser-illuminated surface of the targets. The experiment indicates that the reduction in imprint is at least as large as that obtained by a 6 times improvement in the laser uniformity. We present simulations supported by experiments showing that during the low intensity foot the laser light can be nearly completely absorbed by the high-Z layer. X-rays originating from the high-Z layer heat the underlying lower-Z plastic target material and cause large buffering plasma to form between the layer and the accelerated target. This long-scale plasma apparently isolates the target from laser nonuniformity and accounts for the observed large reduction in laser imprint. With onset of the higher intensity main pulse, the high-Z layer expands and the laser light is transmitted. This technique will be useful in reducing laser imprint in pellet implosions and thereby allow the design of more robust targets for high-gain laser fusion. Prescribed by ANSI Std Z39-18 2 shape needed for high-gain fusion implosions. Imprint of laser nonuniformity during start up of the low intensity foot is a well-known seed for hydrodynamic instability. We observe large reductions in hydrodynamic instability seeded by laser...

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Introduction to Laser-Plasma Interaction and Its Applications

Atzeni

2001

Atoms, Solids, and Plasmas in Super-Intense Laser Fields

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A model of laser imprinting

Abstract: An analytical model is developed to gain physical insight of the laser imprint Summary • Laser nonuniformities imprint surface modulations that degrade the symmetry of implosion.

Cited by 83 publications

References 32 publications

Richtmyer–Meshkov instability: theory of linear and nonlinear evolution

Richtmyer–Meshkov instability: theory of linear and nonlinear evolution

Effects of thin high-Z layers on the hydrodynamics of laser-accelerated plastic targets

Introduction to Laser-Plasma Interaction and Its Applications

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