Real temperature calculation of shock wave driven by sub-nanosecond laser pulses

Temperature is one of the most important parameters for characterizing the thermodynamic state of matter in extreme conditions. However, there is as of yet no universal and accurate way to measure the temperature associated with a shock wave propagating in an opaque material, let alone an inversion method for determining how this temperature evolves. Based on the current strong generalization and learning abilities of artificial neural networks, this paper proposes using an artificial neural network to determine (i) how the shock-wave temperature in a material evolves and (ii) the surface temperature of the interface between the material and vacuum when a shock wave propagates through the material. Data generated using a one-dimensional numerical hydrodynamic simulation are used to train the artificial neural network by applying backpropagation and optimization to many datasets. Once the artificial neural network is trained sufficiently, it becomes an excellent approximator that can estimate the shock-wave temperature from a given streaked-optical-pyrometer image and other known information from the experiment. The paper ends with various possible extensions to the present research.

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Inverting shock-wave temperatures via artificial neural networks

Zhang-Ming

Guo

Huang

et al. 2020

Journal of Applied Physics

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Effect of soft and hard x-rays on shock propagation, preheating, and ablation characteristics in pure and doped Be ablators

Ghosh

Mishra

2022

Physics of Plasmas

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Detailed investigations are carried out on shock, preheat, and ablation characteristics in x-ray driven beryllium based targets, a candidate ablator material for many inertial confinement fusion studies due to its high mass ablation rate. The study involves extensive radiation hydrodynamic simulations performed on pure and 1% copper doped beryllium foils irradiated by a temperature drive source consisting of both Planckian and Gaussian distributions with peaks lying in soft and hard x-ray regions, respectively. The results of steady state x-ray driven ablation and radiant heat exchange in a sub-critical shock are extended to a non-Planckian source. Based on that, new scaling relations are proposed for shock velocity, shock breakout temperature, maximum preheat temperature, and mass ablation rate with the temperature ([Formula: see text] eV) and the fraction of total energy density due to Gaussian distribution ([Formula: see text]) of the incident drive. All parameters increase with drive temperature strength, but the presence of hard x rays does not affect them uniformly. Among all, preheat and shock breakout temperature exhibit a strong dependence on fraction of hard x rays present in the drive spectrum. The effect of doping translates into a pronounced decrease in preheat and shock breakout temperature, while mass ablation rate reduces marginally. The resulting variations in different parameters are explained on the basis of distribution of total extinction coefficient over the spectral form of an incident drive source.

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On characterization of shock propagation and radiative preheating in x-ray driven high-density carbon foils

Mishra

Ghosh

2023

Physics of Plasmas

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Recently, much effort has been dedicated to the high-density carbon ablator coated fuel capsule in indirect drive inertial confinement fusion experiments due to its higher density compared to other ablators. By using detailed radiation hydrodynamic simulations over a broad range of drive and target parameters, a thorough analysis is performed on shock speed, shock breakout, and maximum preheating temperature in pure and tungsten doped high density carbon foils. The ablators are irradiated by a non-equilibrium x-ray temperature drive consisting of the usual Planckian plus an additionally imposed Gaussian distribution lying in the high frequency M-band region of the incident spectrum. All variables have shown a complex interdependence on strength of the drive, its spectral distribution, and the thickness of the target. Maximum preheating temperature, an important parameter in designing experiments, reduces up to 34% for thicker high-density carbon (HDC) foils, whereas a mere 0.44% doping of tungsten in pure HDC is able to reduce preheating up to 17% for extreme drive conditions. The results are explained on the basis of variation of average albedo/wall loss behavior in foils, an outcome of the interplay between total extinction coefficient and spectral intensity variation with photon energy. For a better understanding and comparison among different types of ablators, multi-parameter scaling relations are proposed for above-mentioned variables, which govern the dynamics of shock propagation and preheating phenomena in HDC based foils.

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Real temperature calculation of shock wave driven by sub-nanosecond laser pulses

Cited by 4 publications

References 14 publications

Inverting shock-wave temperatures via artificial neural networks

Inverting shock-wave temperatures via artificial neural networks

Effect of soft and hard x-rays on shock propagation, preheating, and ablation characteristics in pure and doped Be ablators

On characterization of shock propagation and radiative preheating in x-ray driven high-density carbon foils

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