Measurements of inverse bremsstrahlung absorption and non-Maxwellian electron velocity distributions

Liu, J.M.; Groot, J. S. De; Matte, J. P.; Johnston, T. W.; Drake, R. P.

doi:10.1103/physrevlett.72.2717

Cited by 158 publications

(76 citation statements)

References 16 publications

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“…In fact, the non-Maxwellian velocity distributions for electrons in plasma were already measured in the experiment where the temperature gradient was steep [7]. And the non-Maxwellian velocity distributions for ions were also reported in the studies of the earth' plasma sheet, the solar wind, and elsewhere the long-range interacting systems containing plentiful superthermal particles, i.e., the particles with the speeds faster than the thermal speed [8,9].…”

Section: ．Introductionmentioning

confidence: 82%

Ion acoustic waves in the plasma with the power-law q-distribution in nonextensive statistics

Liu

2008

Physica A: Statistical Mechanics and its Applications

189

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Abstract:We investigate the dispersion relation and Landau damping of ion acoustic waves in the collisionless magnetic-field-free plasma if it is described by the nonextensive -distributions of Tsallis statistics. We show that the increased numbers of superthermal particles and low velocity particles can explain the strengthened and weakened modes of Landau damping, respectively, with the -distribution. When the ion temperature is equal to the electron temperature, the weakly damped waves are found to be the distributions with small values of . . It is known that there are two models for the ion acoustic waves [4]: one is the continuum models, in which the plasma is treated as a fluid and so the fluid dynamics is used for its theoretical studies; the other one is based on the kinetic equations in statistical theory, where the distribution functions are used to describe the properties of the ion acoustic waves. As is well-known, Maxwellian distribution in Boltzmann-Gibbs (B-G) statistics is believed valid universally for the macroscopic ergodic equilibrium systems, but for the systems with the long-range interactions, such as plasma and gravitational systems, where the non-equilibrium stationary states exist, Maxwellian distribution might be inadequate for the description of the systems. For example, the experimentally measured phase velocity of the ion acoustic waves was 70% higher than the theoretical value derived under the presupposition that the plasma is described by Maxwellian distribution [5]. In the experiment for measuring the ion acoustic waves, the energy distribution of electrons may be actually not the Maxwellian one and hence we are hard to determine the valid electron temperature [6]. In fact, the non-Maxwellian velocity distributions for electrons in plasma were already measured in the experiment where the temperature 1

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Section: ．Introductionmentioning

confidence: 82%

Ion acoustic waves in the plasma with the power-law q-distribution in nonextensive statistics

Liu

2008

Physica A: Statistical Mechanics and its Applications

189

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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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“…The findings of the present investigation may be useful for the modulation of dust-ion acoustic wave envelopes in dusty superthermal plasmas such as those in laboratory [36], space [37][38][39] and astrophysical [40] environments.…”

Section: Discussionmentioning

confidence: 99%

Amplitude modulation of three-dimensional low-frequency solitary waves in a magnetized dusty superthermal plasma

2017

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The amplitude modulation of three-dimensional (3D) dust ion-acoustic wave (DIAW) packets is studied in a collisionless magnetized plasma with inertial positive ions, superthermal electrons and negatively charged immobile dust grains. By using the reductive perturbation technique, a 3D-nonlinear Schrödinger equation is derived, which governs the slow modulation of DIAW packets. The latter are found to be stable in the low-frequency ðx\x c

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Measurements of inverse bremsstrahlung absorption and non-Maxwellian electron velocity distributions

Cited by 158 publications

References 16 publications

Ion acoustic waves in the plasma with the power-law q-distribution in nonextensive statistics

Ion acoustic waves in the plasma with the power-law q-distribution in nonextensive statistics

Kinetic modeling of Nernst effect in magnetized hohlraums

Amplitude modulation of three-dimensional low-frequency solitary waves in a magnetized dusty superthermal plasma

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