A model for the electron thermal conductivity of a two-component,strongly coupled plasma

An expression for the electron thermal conductivity in the two-component strongly coupled plasmas is derived. The new formulation is examined in the context of laser fusion plasmas, using static correlations derived from the hypernetted chain equations. The model yields results in good agreement with molecular dynamics simulations.     

Suppression of nonlocal thermal conductivity in a turbulent plasma

It is shown that anomalous suppression of the electronic thermal conductivity occurs in a weakly collisional plasma as a result of electron scattering not only by charged particles but also by low-frequency turbulent fluctuations. Pis’ma Zh. éksp. Teor. Fiz. 63, No. 8, 579–582 (25 April 1996)     

Theory of thermal conductivity in the disordered electron liquid

We study thermal conductivity in the disordered two-dimensional electron liquid in the presence of long-range Coulomb interactions. We describe a microscopic analysis of the problem using the partition function defined on the Keldysh contour as a starting point. We extend the renormalization group (RG) analysis developed for thermal transport in the disordered Fermi liquid and include scattering processes induced by the long-range Coulomb interaction in the sub-temperature energy range. For the thermal conductivity, unlike for the electrical conductivity, these scattering processes yield a logarithmic correction that may compete with the RG corrections. The interest in this correction arises from the fact that it violates the Wiedemann–Franz law. We checked that the sub-temperature correction to the thermal conductivity is not modified either by the inclusion of Fermi liquid interaction amplitudes or as a result of the RG flow. We therefore expect that the answer obtained for this correction is final. We use the theory to describe thermal transport on the metallic side of the metal–insulator transition in Si MOSFETs.     

Contribution of thermal radiation in measurements of thermal conductivity of sandstone

The effective thermal conductivity of sandstone at high pressures of up to 400 MPa and temperatures of 273–523 K has been studied. It has been shown that the degree of crystallization of rock-forming minerals substantially influences the temperature and pressure dependences of the thermal conductivity. The contribution of the radiation heat transfer in measurements of the thermal conductivity of sandstone at various temperatures has been analyzed taking into account the reflection and attenuation of the thermal radiation. The results of measuring the reflection and absorption spectra of the thermal radiation have been presented.     

Anomalous electron thermal conductivity across the destroyed magnetic surfaces

New “Semicollisional” regime of the anomalous electron transport pertaining to the weakly collisional plasma is described in the paper. The transition from the collisionless to semicollisional case is determined by the ratio of the phase stochastization length of the parallel electron motion to the mean free path. It was shown also that the anomalous thermal conductivity can be described by the known “selfsimilar” expression $\text{χ}{}_{\mathrm{?}}\text{= χ}{}_{6e}\text{Ь}{}^2{}_0$ only for very strong collisions or high level of magnetic field turbulence.     

Electrothermal efficiency, temperature and thermal conductivity of plasma jet in a DC plasma spray torch

A study was made to evaluate the electrothermal efficiency of a DC arc plasma torch and temperature and thermal conductivity of plasma jet in the torch. The torch was operated at power levels from 4 to 20 kW in non-transferred arc mode. The effect of nitrogen in combination with argon as plasma gas on the above properties was investigated. Calculations were made from experimental data. The electrothermal efficiency increased significantly with increase in nitrogen content. The plasma jet temperature and thermal conductivity exhibited a decrease with increase in nitrogen content. The experiment was done at different total gas flow rates. The results are explained on the basis of dissociation energy of nitrogen molecules and plasma jet energy loss to the cathode, anode and the walls of the torch     

Measurements of the electron concentration and conductivity of a partially ionized inert gas plasma

A theoretical model for the resonant hyper-Raman scattering in semiconductor crystals is presented. The Wannier excitons are considered as intermediate states. The expressions for the resonant hyper-Raman scattering cross section are obtained. The theoretical model developed allows taking into account different mechanisms of the exciton-photon and exciton-phonon interactions.     

Comparative study of textured diamond films by thermal conductivity measurements

Superior thermal conductivity, high resistance, high breakdown voltage and wide band gap make diamond an attractive material for a variety of applications in electronics. One of its most appealing applications is as a buried dielectric in silicon-on-diamond (SOD) technology. This paper presents thermal conductivity measurements conducted on a series of diamond films (grown by the microwave plasma chemical vapor deposition technique) as a function of the sample morphology and thickness, for eventual incorporation in the SOD structures. Results show that there is a significant difference in the measured thermal conductivity between samples with fiber texture and samples with sheet texture. Also, measurements performed on a 160-μm-thick diamond sample before and after reactive ion etching of approximately 10 μm of the nucleation layer show no significant change in the measured value of the thermal conductivity. PACS 81.05.Uw; 65.40.-b; 61.72.-y     

Thermal lensing measurements and thermal conductivity of Yb:YAB

By using holographic shear interferometry, we have measured the thermal lens in a diode-pumped Yb:YAB crystal, under lasing and non-lasing conditions, as a function of absorbed power. From these purely optical measurements we estimate the fractional thermal loading and the thermal conductivity of Yb:YAB. Knowledge of these thermal parameters is essential for the optimisation of Yb:YAB laser cavity designs. Received: 5 February 2002 / Final version: 22 November 2002 / Published online: 26 February 2003 RID="*" ID="*"Corresponding author. Fax +61-2/9850-8915, E-mail: Judith@ics.mq.edu.au     

Probe measurements in a plasma having an anisotropic electron velocity distribution function

In this paper a number of questions connected with the diagnostics of anisotropic electron velocity distribution functions possessing a drift velocity were examined. In an example involving a model distribution function, the possible errors in measurements of the electron energy distribution function (EEDF) using a cylindrical probe oriented parallel to the particle flow are estimated. It is shown that application of a standard method for treating probe volt-ampere characteristics leads to over- and underestimates relative to the true values of the measured temperatures T _e ⁺ and T _e ^– , found respectively according to the currents i⁺(V) and i^–(V) on a flat probe, oriented along and against a specific direction. A comparison of calculated T _e ⁺ +/T _e ^– ratios is made with experimental data.Translated from Izvestiya Vysshikh Uchebnykh Zavedenii, Fizika, No. 9, pp. 9–13, September, 1990.     

Simultaneous measurements of the torsional oscillator anomaly and thermal conductivity in solid 4He

In these torsional oscillator experiments, the samples of solid (4)He were characterized by measuring their thermal conductivity. Polycrystalline samples of helium of either high isotopic purity or natural concentration of (3)He were grown in an annular container by the blocked-capillary method and investigated before and after annealing. No correlation has been found between the magnitude of the low-temperature shift of the torsional oscillator frequency and the amount of crystalline defects as measured by the thermal conductivity. In samples with the natural (3)He concentration, a substantial excess thermal conductivity over the usual T(3) dependence was observed below 120 mK.     

Determination of thermal conductivity of CVD diamond films via photoacoustic measurements

A novel method of determination of polycrystalline diamond films’ thermoconductive properties using the photoacoustic effect is proposed. By this method, we studied the diamond films grown on silicon substrates using chemical vapor deposition technique. A value of thermal conductivity obtained for the films was less than half that for diamond single crystal. The decrease of thermal conductivity, as well as characteristic features of optical properties of the films, is explained by the presence of a large amount of intercrystallite boundaries and other structure defects and admixures detected using Raman and photoluminescent spectroscopies. Received: 22 October 1998 / Accepted: 27 January 1999 / Published online: 28 April 1999     

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用高密度等离子体模型可以计算出一整套输运参数,并且在很宽的等离子体温度和密度范围内有合理的精度,可广泛应用于Z箍缩等离子体、激光聚变和磁约束聚变等领域,并将这个模型计算出的各种输运参数拟合成了实用的公式。     

Infrared thermography protocol for simple measurements of thermal diffusivity and conductivity

An accurate characterization of thermal properties requires the knowledge of both thermal diffusivity and conductivity. Most of the time, the thermal conductivity have to be measured with complicated setups. In this paper, we show that a combination of two experiments carried out with the same setup – stimulated infrared thermography – allows to estimate straightforwardly and quickly the absolute value of the thermal diffusivity and the thermal conductivity relatively to a reference material.     

Anisotropy of the electron mean free path in the thermal conductivity of very pure gallium

In order to determine the anisotropy of the bulk mean free pathl _b, we have measured the thermal conductivity of 6–9's pure gallium single crystals as a function of size and crystal orientation between 1.4 and 4.2°K. The results were analyzed by adapting the existing theory for the electrical conductivity of thin wires to the thermal case. The results show that the reciprocal of the bulk mean free path can be expressed as a linear function ofT ³ for all three orientations. The residual contributions to this quantity are highly anisotropic, as expected. The electron-phonon contributions are, on the other hand, nearly equal in magnitude and exhibit a ratio of 3:4:4 for the A:B:C axis, respectively. In addition, an unusual dependence upond ⁻², whered is the specimen diameter, was observed for the C-axis. It is possibly related to the fact that for this direction only 6% of the entire free electron Fermi surface takes part in conduction which, as a consequence, may be largely dominated by Umklapp scattering. Research sponsored by the Air Force Office of Scientific Research, Office of Aerospace Research, United States Air Force under Grant No. AF-AFOSR 1051-66.     

Laser interferometric measurements of electron density in an arc plasma

The paper describes the application of a laser interferometric technique to arc discharges operating at atmospheric pressure. The limitations of this method are discussed in detail. Results are given for the axial electron density in an argon arc, tube 5 mm diameter, over a current range 30–75 A. In addition the decay of the electron density following rapid arc interruption is also given. It is shown that the time constant of the conductance decay which can be derived from the preceeding measurements is in very good agreement with experimental values determined directly.     

Direct observation of anomalously low longitudinal electron heat conductivity in the course of collective relaxation of a high-current relativistic electron beam in plasma

JETP Letters - The experimental results on a multiple-mirror trap GOL-3 with a short section of reduced magnetic field (“magnetic pit”) are presented. The reduced specific energy...