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1

Digitale Medien

Growth rate reduction of the Rayleigh–Taylor instability by ablative convection (1995)

Wouchuk, J. G. ; Piriz, A. R.

[S.l.] : American Institute of Physics (AIP)

Physics of Plasmas 2 (1995), S. 493-500

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ISSN: 1089-7674

Quelle: AIP Digital Archive

Thema: Physik

Notizen: A simple model for the instability of a steady ablation front is presented. The model is based on the sharp boundary approximation, but it is considered that, as far as the Rayleigh–Taylor instability regards, the front thickness is of the order of the minimum scale length of the density gradient. The model yields a general analytical expression for the linear growth rate, which does not depend explicitly on the particular process of energy deposition, which drives the ablation. For the specific case of electronic thermal conduction the model is in good agreement with previously reported numerical calculations. The growth rate results to be well fitted by the so-called Takabe formula, and the coefficients in such a formula are analytically derived. © 1995 American Institute of Physics.

Materialart: Digitale Medien

URL: http://dx.doi.org/10.1063/1.870974

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2

Digitale Medien

Direct-drive hydrodynamic instability experiments on the GEKKO XII laser (1997)

Azechi, H. ; Nakai, M. ; Shigemori, K. ; [weitere]

[S.l.] : American Institute of Physics (AIP)

Physics of Plasmas 4 (1997), S. 4079-4089

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ISSN: 1089-7674

Quelle: AIP Digital Archive

Thema: Physik

Notizen: Hydrodynamic instabilities, such as the Rayleigh–Taylor (R–T) instability, play a critical role in inertial confinement fusion as they finally cause fuel-pusher mixing that potentially quenches thermonuclear ignition. Good understanding of the instabilities is necessary to limit the mixing within a tolerable level. A series of experiments has been conducted on the GEKKO XII laser facility [C. Yamanaka et al., IEEE J. Quantum Electron. QE-17, 1639 (1981)] to measure hydrodynamic instabilities in planar foils directly irradiated by 0.53 μm laser light. It has been found that (1) the imprint is reasonably explained by an imprint model based on the equation of motion with the pressure perturbation smoothed by the cloudy-day effect, and (2) the experimental R–T growth rate is significantly reduced from the classical growth rate due probably to ablative stabilization enhanced by nonlocal heat transport. © 1997 American Institute of Physics.

Materialart: Digitale Medien

URL: http://dx.doi.org/10.1063/1.872528

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3

Digitale Medien

Growth rate of the Richtmyer–Meshkov instability when a rarefaction is reflected (2001)

Wouchuk, J. G.

[S.l.] : American Institute of Physics (AIP)

Physics of Plasmas 8 (2001), S. 2890-2907

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ISSN: 1089-7674

Quelle: AIP Digital Archive

Thema: Physik

Notizen: A model is presented that calculates the asymptotic growth rate of the linear Richtmyer–Meshkov instability when a rarefaction is reflected at the contact surface. The result is valid for any value of the incident shock Mach number and initial fluids parameters. There is very good agreement with previous numerical simulations and experiments done at high compressions. The technique developed in the model is seen to be highly accurate and allows us a fast evaluation of the asymptotic normal velocity at the interface. © 2001 American Institute of Physics.

Materialart: Digitale Medien

URL: http://dx.doi.org/10.1063/1.1369119

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4

Digitale Medien

Hydrodynamic perturbation growth in start-up phase in laser implosion : The 39th annual meeting of division of plasma physics of APS (1998)

Nishihara, K. ; Ishizaki, R. ; Wouchuk, J. G. ; [weitere]

[S.l.] : American Institute of Physics (AIP)

Physics of Plasmas 5 (1998), S. 1945-1952

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ISSN: 1089-7674

Quelle: AIP Digital Archive

Thema: Physik

Notizen: Nonuniform laser ablation caused by nonuniform laser irradiation and initial target roughness induces ripples of shock and ablation surfaces in laser implosion. Hydrodynamic perturbation growth before the shock breakout is investigated by using an analytical model and two-dimensional simulations. The model agrees well with simulation and experimental results. Areal mass density perturbations and growth rate of the Richtmyer–Meshkov instability are estimated for an ignition target. The thermal smoothing in the ablation layer is also studied for perturbations with a wavelength longer than the layer thickness. A large increase of temperature and density perturbations is shown instead of the smoothing for such a wavelength. © 1998 American Institute of Physics.

Materialart: Digitale Medien

URL: http://dx.doi.org/10.1063/1.872864

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5

Digitale Medien

Laser implosion of gas-filled microballoons (1992)

Piriz, A. R. ; Giudice, G. E. ; Wouchuk, J. G.

New York, NY : American Institute of Physics (AIP)

Physics of Fluids 4 (1992), S. 693-700

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ISSN: 1089-7666

Quelle: AIP Digital Archive

Thema: Physik

Notizen: A relatively simple model for the implosion of a strong shock driven by a spherical shell which is ablatively imploded by a laser pulse is presented. The dynamics of the shock and the shell is completely described by three dimensionless parameters containing all the information regarding the laser and the target. The model is applied to recent experiments which produce the highest neutron yield, and a good agreement with simulations and experimental results is found.

Materialart: Digitale Medien

URL: http://dx.doi.org/10.1063/1.860267

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6

Digitale Medien

Implosion of a two-layer shell driven by a shaped pressure pulse (1991)

Piriz, A. R. ; Wouchuk, J. G.

New York, NY : American Institute of Physics (AIP)

Physics of Fluids 3 (1991), S. 2889-2897

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ISSN: 1089-7666

Quelle: AIP Digital Archive

Thema: Physik

Notizen: An analytical model for the implosion of a two-layer spherical shell target driven by a two-step pressure pulse is developed. The process of formation of the central spark is approximately described and the effect of the prepulse on the final stage of fuel and pusher is studied. The size of the central spark is determined by the thermal conduction, and scaling laws relating the temperature and density of the spark with the parameters of the fuel and the pulse are found. These scaling laws can be useful in the design of high-gain targets for inertial confinement fusion.

Materialart: Digitale Medien

URL: http://dx.doi.org/10.1063/1.859922

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