scholarly journals A Thermodynamic Treatment of Anisotropic Diffusion in an Electric Field

1972 ◽  
Vol 25 (6) ◽  
pp. 685 ◽  
Author(s):  
RE Robson
Keyword(s):  
Boltzmann Equation ◽  
Electric Field ◽  
Drift Velocity ◽  
Anisotropic Diffusion ◽  
Diffusion Tensor ◽  
Charged Particles ◽  
Equilibrium Thermodynamics ◽  
Neutral Gas ◽  
The Boltzmann Equation ◽  
Diffusive Processes

Non-equilibrium thermodynamics is used to analyse the diffusive processes associated with a swarm of charged particles (ions or electrons) drifting in a neutral gas under the influence of an electric field. A simple approximate phenomenological relationship connecting components of the diffusion tensor with the drift velocity of the swarm is derived and the utility of the formula is illustrated in several cases where previous analyses have been carried out using the Boltzmann equation.

scholarly journals Calculation of Electron Swarm Parameters in Tetrafluoromethane

2020 ◽  
Vol 8 (2) ◽  
pp. 22-28
Author(s):  
Idris H. Salih ◽  
Mohammad M. Othman ◽  
Sherzad A. Taha
Keyword(s):  
Boltzmann Equation ◽  
Field Strength ◽  
Electric Field ◽  
Cross Sections ◽  
Electron Attachment ◽  
High Energy ◽  
Longitudinal Diffusion ◽  
Characteristic Energy ◽  
The Boltzmann Equation ◽  
High Energy Tail

The electron swarm parameters and electron energy distribution function (EEDF) are necessary, especially onunderstanding quantitatively plasma phenomena and ionized gases. The EEDF and electron swarm parameters including the reduce effective ionization coefficient (α-η)/N (α and η are the ionization and attachment coefficient, respectively), electron drift velocity, electron mean energy, characteristic energy, density  normalized longitudinal diffusion coefficient, and density normalized electron mobility in tetrafluoromethane (CF4) which was analyzed and calculated using the two-term approximation of the Boltzmann equation method at room temperature, over a range of the reduced electric field strength (E/N) between 0.1 and 1000 Td(1Td=10-17 V.cm2), where E is the electric field and N is the gas density of the gas. The calculations required cross-sections of the electron beam, thus published momentum transfer, vibration, electronic excitation, ionization, and attachment cross-sections for CF4 were used, the results of the Boltzmann equation in a good agreement with experimental and theoretical values over the entire range of E/N. In all cases, negative differential conductivity regions were found. It is found that the calculated EEDF closes to Maxwellian distribution and decreases sharply at low E/N. The low energy part of EEDF flats and the high-energy tail of EEDF increases with increase E/N. The EEDF found to be non-Maxwellian when the E/N> 10Td, havingenergy variations which reflect electron/molecule energy exchange processes. In addition, limiting field strength (E/N)limit has been calculated from the plots of (α-η)/N, for which the ionization exactlybalances the electron attachment, which is valid for the analysis of insulation characteristics and application to power equipment.

scholarly journals On the Drift Velocity of Electrons in a Gas

1972 ◽  
Vol 25 (3) ◽  
pp. 329
Author(s):  
SL Paveri-Fontana
Keyword(s):  
Steady State ◽  
Electric Field ◽  
Drift Velocity ◽  
Isotropic Scattering ◽  
Uniform Electric Field ◽  
Present Communication ◽  
Steady State Distribution ◽  
State Distribution ◽  
Neutral Gas

In a recent paper, Crompton, Elford, and Robertson (1970; hereafter referred to as CER) considered certain questions concerning the steady-state distribution of electrons moving in a neutral gas under the influence of a uniform electric field E. The present communication comments on some aspects of the error discussion in the Appendix of the paper by CER. The analysis will be restricted to the case of isotropic scattering.

scholarly journals Cross Sections for Electron?Carbon Monoxide Collisions in the Range 1?4 eV

1983 ◽  
Vol 36 (4) ◽  
pp. 473 ◽  
Author(s):  
GN Haddad ◽  
HB Milloy
Keyword(s):  
Boltzmann Equation ◽  
Energy Range ◽  
Drift Velocity ◽  
Cross Sections ◽  
Velocity Distribution Function ◽  
Gas Mixtures ◽  
Transport Parameter ◽  
Velocity Data ◽  
The Boltzmann Equation ◽  
Term Approximation

The scattering of electrons from CO molecules has been studied over the energy range from 1 to 4 eV by analysing drift velocity data for pure CO and CO-inert gas mixtures at 294 K. The validity of using the so-called 'two term approximation' for the velocity distribution function in the solution of the Boltzmann equation to analyse drift velocity data for the pure gas (and thus also for the gas mixtures) has been established. The momentum transfer cross section for CO has been determined in the energy range 1-4 eV, and the measurements of the vibrational cross sections by Ehrhardt et al. (1968) have been renormalized. By using a solution of the Boltzmann equation which avoids the two term approximation, these cross sections have been shown to be consistent with previous measurement.s of the transport parameter D 1.1 fl in pure CO.

scholarly journals On the Theory of Anisotropic Diffusion of Electrons in Gases

1972 ◽  
Vol 25 (1) ◽  
pp. 43 ◽  
Author(s):  
LGH Huxley
Keyword(s):  
Distribution Function ◽  
Steady State ◽  
Boltzmann Equation ◽  
Electric Field ◽  
Current Density ◽  
Anisotropic Diffusion ◽  
Electric Force ◽  
Theoretical Discussion ◽  
Number Density ◽  
Coefficient Of Diffusion

It is now recognized that when electrons move in a steady state of motion in a gas in an electric field the process of diffusion is in general anisotropic with a coefficient of diffusion DL along or against the electric force eE that is not the same as the coefficient D for directions normal to eE. A theoretical discussion of this phenomenon based upon the Maxwell?Boltzmann equation is given which also entails consideration of related matters such as the distribution function for an isolated travelling group, the distribution of number density n, the equation of continuity and current density, and the relation of the theory of the travelling group to that of the steady stream.

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