Steady-state planar ablative flow

Manheimer, Wallace M.; Colombant, D.; Gardner, John

doi:10.1063/1.863956

Cited by 195 publications

(79 citation statements)

References 31 publications

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“…The simulations show quasi-isothermal plasma ablation [23] with initial electron temperatures T e near 800 eV driving a supersonic ablation stream flowing from each target with V ≈ C s + x/t, and density n ≈ n ab exp(−αx/C s t). where C s ≈ 2 × 10 5 m/s is the sound speed, x measures distance from the ablation surface, and t time.…”

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confidence: 99%

Filamentation Instability of Counterstreaming Laser-Driven Plasmas

et al. 2013

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Filamentation due to the growth of a Weibel-type instability was observed in the interaction of a pair of counter-streaming, ablatively-driven plasma flows, in a supersonic, collisionless regime relevant to astrophysical collisionless shocks. The flows were created by irradiating a pair of opposing plastic (CH) foils with 1.8 kJ, 2-ns laser pulses on the omega ep laser system. Ultrafast laserdriven proton radiography was used to image the Weibel-generated electromagnetic fields. The experimental observations are in good agreement with the analytical theory of the Weibel instability and with particle-in-cell simulations.Astrophysical shock waves play diverse roles, including energizing cosmic rays in the blast waves of astrophysical explosions [1], and generating primordial magnetic fields during the formation of galaxies and clusters [2]. These shocks are typically collisionless, and require collective electromagnetic fields [3], as Coulomb collisions alone are too weak to sustain shocks in high-temperature astrophysical plasmas. The class of Weibel-type instabilities [4][5][6] (including the classical Weibel and currentfilamentation instabilities) is one such collective mechanism that has been proposed to generate a turbulent magnetic field in the shock front and thereby mediate shock formation in cosmological shocks [7] and blast wave shocks in gamma ray bursts [8][9][10] and supernova remnants [11]. These instabilities generate magnetic field de novo by tapping into non-equilibrium features in the electron and ion distributions functions. The classical form of the Weibel instability is driven by temperature anisotropy [4], but counterstreaming ion beams, as occurs in the present context, provides an equivalent drive mechanism [6]. A related current filamentation instability of relativistic electron beams [12] has also previously been observed in experiments driven by ultraintense lasers [13].We report experimental identification an ion-driven Weibel-type instability generated in the interaction of two counterstreaming laser-produced plasma plumes. A pair of opposing CH targets was irradiated by kJ-class laser pulses on the OMEGA EP laser laser system, driving a pair of ablative flows toward the collision region at the midplane between the two foils. Due to the long mean-free-path between ions in opposing streams, the streams interpenetrate, establishing supersonic counterstreaming conditions in the ion populations, while the electrons form a single thermalized cloud. Meanwhile, the plasma density is also sufficient so that the the ion skin depth d i = (m i /µ 0 ne 2 ) 1/2 , is much smaller than the system size L. These conditions allow the growth of an ion-driven Weibel instability, for which d i is the characteristic wavelength [14][15][16]. The Weibel-generated electromagnetic fields were observed with an ultrafast pro- ton radiography technique [17], and identified through good agreement with analytic theory [6] and particle-incell simulations, discussed below. Figure 1 shows a schematic of the experiments...

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Filamentation Instability of Counterstreaming Laser-Driven Plasmas

et al. 2013

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“…4, but for a laser wavelength of 0:248 lm. According to the stationary ablation model of Manheimer et al, 5,71 the dependences of the ablation pressure p a and mass ablation rate _ m on laser wavelength are given by…”

Section: Phys Plasmas 23 122701 (2016)mentioning

confidence: 99%

Numerical simulations of the ablative Rayleigh-Taylor instability in planar inertial-confinement-fusion targets using the FastRad3D code

et al. 2016

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The ablative Rayleigh-Taylor (RT) instability is a central issue in the performance of laser-accelerated inertial-confinement-fusion targets. Historically, the accurate numerical simulation of this instability has been a challenging task for many radiation hydrodynamics codes, particularly when it comes to capturing the ablatively stabilized region of the linear dispersion spectrum and modeling ab initio perturbations. Here, we present recent results from two-dimensional numerical simulations of the ablative RT instability in planar laser-ablated foils that were performed using the Eulerian code FastRad3D. Our study considers polystyrene, (cryogenic) deuterium-tritium, and beryllium target materials, quarter- and third-micron laser light, and low and high laser intensities. An initial single-mode surface perturbation is modeled in our simulations as a small modulation to the target mass density and the ablative RT growth-rate is calculated from the time history of areal-mass variations once the target reaches a steady-state acceleration. By performing a sequence of such simulations with different perturbation wavelengths, we generate a discrete dispersion spectrum for each of our examples and find that in all cases the linear RT growth-rate γ is well described by an expression of the form γ=α [kg/(1+ϵ kLm)]1/2−βkVa, where k is the perturbation wavenumber, g is the acceleration of the target, Lm is the minimum density scale-length, Va is the ablation velocity, and ϵ is either one or zero. The dimensionless coefficients α and β in the above formula depend on the particular target and laser parameters and are determined from two-dimensional simulation results through the use of a nonlinear curve-fitting procedure. While our findings are generally consistent with those of Betti et al. (Phys. Plasmas 5, 1446 (1998)), the ablative RT growth-rates predicted in this investigation are somewhat smaller than the values previously reported for the same target and laser parameters. It is speculated that differences in the equation-of-state and opacity models are largely responsible for the discrepancy. Resolution of this issue awaits the development of better experimental diagnostics capable of measuring small-wavelength (5–20 μm) perturbation growth due to the ablative RT instability in the linear regime.

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“…Although several theoretical models of plasma expansion were developed already in the 70's and in the 80's [1][2][3] and many experiments have studied this aspect, still there are not many "clean" experimental results. Indeed most experiments are influenced by 2D effects in the hydro expansion of the plasma, which arise as a consequence of the small focal spots, which were needed to produce the relatively high laser intensity of interest in these experiments.…”

Section: Introductionmentioning

confidence: 99%

Time-Resolved Analysis of High-Power-Laser Produced Plasma Expansion in Vacuum

Aliverdiev¹,

Batani²,

Malka³

et al. 2005

AIP Conference Proceedings

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Abstract.Here we consider the results of an experimental investigation of the temporal evolution of plasmas produced by high power laser irradiation of various types of target materials. The experiment was performed at the LULI Laboratory (Ecole Polytechnique, Paris). We have developed a method to analyze time-resolved streak-camera images and analyzed a number of results obtained with various materials.

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Steady-state planar ablative flow

Cited by 195 publications

References 31 publications

Filamentation Instability of Counterstreaming Laser-Driven Plasmas

Filamentation Instability of Counterstreaming Laser-Driven Plasmas

Numerical simulations of the ablative Rayleigh-Taylor instability in planar inertial-confinement-fusion targets using the FastRad3D code

Time-Resolved Analysis of High-Power-Laser Produced Plasma Expansion in Vacuum

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