Radiation-dependent ionization model for laser-created plasmas

Busquet, M.

doi:10.1063/1.860586

Cited by 137 publications

(47 citation statements)

References 62 publications

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“…Note that the averaging given in Eqns. (3) and (4) and the averaging continuing below does not have to be statistical: it could include a Boltzmann factor with the real or effective temperature following the numerical procedure used in the code MOST [9], the code RADIOM [10], or using the analytic form given in Ref. [11].…”

Section: Calculation Of Ratesmentioning

confidence: 99%

Hybrid atomic models for spectroscopic plasma diagnostics

Hansen

Bauche

Bauche‐Arnoult

et al. 2007

High Energy Density Physics

161

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We propose a hybrid approach to treating atomic structure and rates in collisionalradiative models, combining the completeness of highly averaged models with the accuracy of detailed models. The hybrid scheme supplements a small subset of coronally accessible fine structure levels with a complete set of configuration-and superconfiguration-averaged levels and produces spectra based on transitions among a mix of fine-structure and relativistic configuration-averaged levels. Convenient expressions are given for obtaining rates between the fine structure and averaged levels and a technique for propagating configuration interaction from the fine structure calculations to configuration averages is described. We present results from a trial hybrid model of germanium which demonstrate the accuracy of the hybrid model for charge state distributions and spectra.

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Section: Calculation Of Ratesmentioning

confidence: 99%

Hybrid atomic models for spectroscopic plasma diagnostics

Hansen

Bauche

Bauche‐Arnoult

et al. 2007

High Energy Density Physics

161

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“…The velocity profile of the shock obtained from the VISAR is compared to the numerical simulations ( figure 2-b) from the 2D radiation hydrodynamics FCI2 code at CEA [6]; the two results are in good agreement within the error bars. The SESAME 7592 equation of state (EOS) table [7] was used for the sample.…”

Section: Experimental Results and Comparison With Numerical Simulationsmentioning

confidence: 54%

Study of shock-coalescence on the LIL laser facility

Debras

Courtois

Lambert

et al. 2013

EPJ Web of Conferences

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Abstract. We use the LIL (Ligne d'Intégration Laser) facility to study the coalescence of two planar shocks in an indirectly-driven planar sample of polystyrene. This experiment represents the preliminary stage of the future shock-timing campaign for the Laser Megajoule (LMJ). The main objectives are to validate the experimental concept and to test the numerical simulations. We used a gold spherical hohlraum to convert into X-ray the 351 nm wavelength laser pulse and to initiate the two shocks in the sample. To access time resolved shock velocities and temperature, we used two rear-side diagnostics: a VISAR (Velocity Interferometer System for Any Reflection) working at two different wavelengths and a streaked optical selfemission diagnostic. We observed the coalesced shock, in good agreement with the numerical simulations. We also observed a loss of signal during the first nanoseconds probably due to sample heating from the hohlraum X-ray flux. CONTEXTThe LMJ, like the National Ignition Facility (NIF) in the USA, is designed to achieve thermonuclear ignition in an indirect drive scheme, by imploding a spherical capsule filled with a deuterium-tritium (DT) mixture. The best way to efficiently compress the fuel is quasi-isentropic compression. To approximate this compression, a series of four successive centripetal shocks are sent into the sample [1]. The shocks need to be accurately controlled in timing and strength to coalesce at the same time in the gaseous DT close to the inner surface of the cryogenic DT. The first three shocks allow compressing the capsule quasi-isentropically, keeping the cryogenic DT on a low adiabat. The fourth shock drives the final implosion until the ignition. This scheme requires to adjust the laser power time history entering in the gold hohlraum.In this experiment, we seeked to validate the experimental concept in planar geometry and indirect drive for the first two shocks using a truncated LMJ-like pulse shape and to compare the results with numerical simulations. EXPERIMENTAL SETUPFor this experiment we used the LIL laser facility at 3 (351 nm) with an energy of 10 kJ in 12 ns. A spherical gold hohlraum was used to obtain a radiation temperature similar to the first part of the nominal LMJ-drive. Two planar shocks are sent in a planar sample of polystyrene (PS -C 8 H 8 ) fixed on a

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“…(6) was solved in this investigation using an iterative implicit procedure based on the Bi-CGstab numerical algorithm with diagonal pre-conditioning. 64 Although not used here, FastRad3D can also simulate non-LTE effects using the RADIOM method 65 in which an "effective" non-LTE temperature is calculated and then used to reference LTE opacity tables generated by the STA code. Thermal transport in FastRad3D is computed with a fluxlimited, Spitzer-H€ arm diffusion model.…”

Section: The Numerical Modelmentioning

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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Radiation-dependent ionization model for laser-created plasmas

Cited by 137 publications

References 62 publications

Hybrid atomic models for spectroscopic plasma diagnostics

Hybrid atomic models for spectroscopic plasma diagnostics

Study of shock-coalescence on the LIL laser facility

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

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