Electron transport coefficients under super-Gaussian distribution and magnetic field

Huo, Wen Yi; Zeng, Qinghong

doi:10.1063/1.4931743

Cited by 3 publications

(2 citation statements)

References 17 publications

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“…Careful consideration of the electron population with 2v th < v < 4v th is required as these carry most of the heat. Additionally, inverse-bremsstrahlung heating of a plasma [18,19] not only leads to deviations from Braginskii transport [20], but also new transport terms [21,22]. Both non-locality and laser heating result in modifications to the distribution function and nonequilibrium behavior that result in breakdown of the classical transport approximations.…”

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confidence: 99%

Kinetic modeling of Nernst effect in magnetized hohlraums

et al. 2016

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We present nanosecond timescale Vlasov-Fokker-Planck-Maxwell modeling of magnetized plasma transport and dynamics in a hohlraum with an applied external magnetic field, under conditions similar to recent experiments. Self-consistent modeling of the kinetic electron momentum equation allows for a complete treatment of the heat flow equation and Ohm's Law, including Nernst advection of magnetic fields. In addition to showing the prevalence of non-local behavior, we demonstrate that effects such as anomalous heat flow are induced by inverse bremsstrahlung heating. We show magnetic field amplification up to a factor of 3 from Nernst compression into the hohlraum wall. The magnetic field is also expelled towards the hohlraum axis due to Nernst advection faster than frozen-in-flux would suggest. Non-locality contributes to the heat flow towards the hohlraum axis and results in an augmented Nernst advection mechanism that is included self-consistently through kinetic modeling.There has been recent interest in the role of applied magnetic fields in high-energy-density plasmas [1-3] for inertial fusion energy applications [4]. The MagnetoInertial Fusion Electric Discharge System has been developed to provide steady state magnetic fields for long time-scales relative to the experiments. An experiment on the Omega Laser Facility with a 7.5 T external axial magnetic field imposed on an Omega-scale hohlraum measured a rise in observed temperature along the hohlraum axis [5] and modeling showed that external fields can guide hot electrons from laser-plasma interactions [6] through the hohlraum, rather than the capsule [7]. From Ohm's Law, it has been shown that electron heat transport advects such magnetic fields through the Nernst effect [8][9][10][11][12][13][14] in addition to well-known processes like "frozen-in-flow" and resistive diffusion. Dimensionless numbers comparing the ratio of the magnitudes of the Nernst term to the bulk plasma flow term, R N 1 [10], and the Hall term, H N 1 [13], suggest that Nernst convection should be the dominant mechanism for magnetic field transport in a hohlraum. Such a hot and semi-collisional environment is, however, rich in nonequilibrium effects that may complicate the magnetic field dynamics.Laser heating of the plasma results in steep temperature gradients, typically O(3 keV/50 µm). The collisional * archis@ucla.edu † agrt@umich.edu mean-free-path of a 3 keV electron is O(10 µm), depending on the plasma density. Since λ mfp /L < 100, nonlocality can be expected to be important [15]. The steep temperature gradients caused by intense laser heating in a hohlraum have been shown to result in non-local heat flow [16,17]. Careful consideration of the electron population with 2v th < v < 4v th is required as these carry most of the heat. Additionally, inverse-bremsstrahlung heating of a plasma [18,19] not only leads to deviations from Braginskii transport [20], but also new transport terms [21,22]. Both non-locality and laser heating result in modifications to the distribution function an...

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Kinetic modeling of Nernst effect in magnetized hohlraums

et al. 2016

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“…In laser-plasma interaction physics, in order to obtain accurate electron transport coefficients one must consider two effects, one is associated with the self-generated magnetic field and the other is the plasma collision. [9][10][11][12][13] Certainly the electron distribution [14][15][16] has also played a key role. The selfgenerated magnetic field has been studied in laser interacting with plasma over the period of time.…”

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Electronic transport of Lorentz plasma with collision and magnetic field effects

Wan

Jia

et al. 2016

Chinese Phys. B

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The electronic transverse transport of Lorentz plasma with collision and magnetic field effects is studied by solving the Boltzmann equation for different electron density distributions. For the Maxwellian distribution, it is shown that transport coefficients decrease as Ω increases, Ω is the ratio of an electron's magneto-cyclotron frequency to plasma collision frequency. It means that the electrons are possible to be highly collimated by a strong magnetic field. For the quasimonoenergetic distribution with different widths, it is found that the transport coefficients decrease greatly as ε decreases.In particular when the width approaches to zero the transverse transport coefficients are hardly affected by the magnetic field and the minimal one is obtained. Results imply that the strong magnetic field and quasi-monoenergetic distribution are both beneficial to reduce the electronic transverse transport. This study is also helpful to understand the relevant problems of plasma transport in the background of the inertial confinement fusion.

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The nonlocal electron heat transport under the non-Maxwellian distribution in laser plasmas and its influence on laser ablation

Huo

2023

Physics of Plasmas

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The electron heat transport plays an important role in laser driven inertial confinement fusion. For the plasmas created by intense laser, the traditional Spitzer–Härm theory cannot accurately describe the electron heat transport process mainly due to two physical effects. First, the electron distribution function would significantly differ from the Maxwellian distribution because of the inverse bremsstrahlung heating. Second, the long mean free paths of heat carrying electrons relative to the temperature scale length indicate that the electron heat flux has the nonlocal feature. In 2020, we have developed a nonlocal electron heat transport model based on the non-Maxwellian electron distribution function (NM-NL model) to describe the electron heat flux in laser plasmas. Recently, this model is successfully incorporated into our radiation hydrodynamical code RDMG. In this article, we numerically investigated the electron heat flux in laser plasmas, especially the nonlocal feature of heat flux and the influence of the non-Maxwellian distribution. The influence of electron heat transport on laser ablation is also discussed. The simulated plasma conditions based on different electron heat transport models are presented and compared with experiments. Our results show that the nonlocal feature of heat flux and the influence of non-Maxwellian distribution function are considerable in plasmas heated by intense lasers.

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Electron transport coefficients under super-Gaussian distribution and magnetic field

Cited by 3 publications

References 17 publications

Kinetic modeling of Nernst effect in magnetized hohlraums

Kinetic modeling of Nernst effect in magnetized hohlraums

Electronic transport of Lorentz plasma with collision and magnetic field effects

The nonlocal electron heat transport under the non-Maxwellian distribution in laser plasmas and its influence on laser ablation

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