scholarly journals Electron Swarm Parameters and Dielectric Properties of the Superconducting Binary Mixtures of He-H2

2021 ◽  
Vol 36 (1) ◽  
pp. 420-432
Author(s):  
Mohammad M. Othman ◽  
Sherzad A. Taha ◽  
Saeed O. Ibrahim
Keyword(s):  
Distribution Function ◽  
Boltzmann Equation ◽  
Field Strength ◽  
Electric Field ◽  
Dielectric Strength ◽  
Ionization Coefficient ◽  
Experimental Values ◽  
Attachment Coefficient ◽  
Term Approximation ◽  
Effective Ionization

In this study, the electron energy distribution function EEDF, the electron swarm parameters, the effective ionization coefficients, and the critical field strength (dielectric strength) in binary He-H2 gas mixture which used as cryogenic for high-temperature superconducting power application, are evaluated by using two-term approximation of the Boltzmann equation over the range of E/N ( the electric field to gas density) from 1 to 100 Td ( 1 Td=10-17 Vcm2) at temperature 77 K and pressure 2MPa, taking into account elastic and inelastic cross-section. Using the calculated EEDF, the electron swarm parameters (electron drift velocity, mean electron energy, diffusion coefficient, electron mobility, ionization and attachment coefficient) are calculated. At low reduced electric field E/N, the EEDF close Maxwellian distribution, at high E/N, due to vibrational excitation of H2 the calculated distribution function is non-Maxwellian. Besides, in the He-H2 mixture, it is found that increasing small amount of H2 enhances to shift the tail of EEDF to the lower energy region, the reduced ionization coefficient α/N. reduced effective ionization coefficient (α-η)/N) decreases, while, reduced attachment coefficient η/N, reduced critical electric field strength (E/N)crt. and critical electric field Ecrt. Increases, because of hydrogen’s large ionization cross-sections. The dielectric strength of 5% H2 in mixture is in good agreement with experimental values, it is found that dielectric strength depend on pressure and temperature. The electron swarm parameters in pure gaseous helium (He) and hydrogen (H2), in satisfying agreement with previous available theoretical and experimental values. The validity of the calculated values has been confirmed by two-term approximation of the Boltzmann equation analysis.

scholarly journals Ionization and Attachment Coefficients in C4F7N Gas Measured by the Steady-State Townsend Method

2019 ◽  
Vol 9 (18) ◽  
pp. 3686 ◽  
Author(s):  
Zhaoyu Qin ◽  
Yunxiang Long ◽  
Zhenyu Shen ◽  
Cheng Chen ◽  
Liping Guo ◽  
...  
Keyword(s):  
Steady State ◽  
Electric Field ◽  
Electric Fields ◽  
Room Temperature ◽  
Ionization Coefficient ◽  
Ionization Coefficients ◽  
Insulation Performance ◽  
Attachment Coefficient ◽  
Good Agreement ◽  
Effective Ionization

The normalized Townsend first ionization coefficient α/N and normalized attachment coefficient η/N in pure C4F7N were measured by using the steady-state Townsend (SST) method for a range of reduced electric fields E/N from 750 to 1150 Td at room temperature (20 °C). Meanwhile, the effective ionization coefficients are obtained. All SST experimental results show good agreement with pulsed Townsend (PT) experiment results. Comparisons of the critical electric fields of C4F7N with SF6 and other alternative gases such as c-C4F8 and CF3I indicate that C4F7N has a better insulation performance with a much higher normalized critical electric field at 959.19 Td.

scholarly journals On the Validity of the Two-term Approximation of the Electron Distribution Function

1971 ◽  
Vol 24 (4) ◽  
pp. 835 ◽  
Author(s):  
RE Robson ◽  
Kailash Kumar
Keyword(s):  
Distribution Function ◽  
Field Strength ◽  
Drift Velocity ◽  
Electron Distribution ◽  
Electron Distribution Function ◽  
Polynomial Expansion ◽  
Neutral Gas ◽  
Low Field ◽  
Term Approximation ◽  
Field Strengths

The Boltzmann equation for electrons moving in a neutral gas under the influence of an externally applied field is solved by expanding the electron distribution function in terms of Legendre and Sonine polynomials. The solution is given in terms of infinite matrices which have elements ordered by the Sonine polynomial index, and which are dependent upon the field strength. From the structure of the formulae, it is possible to infer that truncation of the Legendre polynomial expansion after two terms is a good approximation at all field strengths. This is supported by calculations of the electron drift velocity at low field strengths, which show that the error introduced by making the two-term approximation is small, even when the deviation from equilibrium is significant. The convergence of the Sonine polynomial expansion is shown to be strongly depende:r;J.t upon field strength, and large matrices are required in the drift velocity formula at even small field strengths.

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.

The Corona breakdown of aerials in air at low pressures

1963 ◽  
Vol 271 (1347) ◽  
pp. 551-564 ◽  
Keyword(s):  
Field Strength ◽  
Electric Field ◽  
Radio Frequency ◽  
Critical Field ◽  
Diffusion Theory ◽  
Reduced Pressure ◽  
Radiated Power ◽  
Diffusion Controlled ◽  
Experimental Values ◽  
Low Pressures

Radio-frequency corona breakdown of the air surrounding a transmitting aerial operating under conditions of reduced pressure occurs for a comparatively low radiated power. In this paper the theory of diffusion-controlled breakdown is discussed and used to deduce the critical field strength for breakdown at the tip of a prolate spheroidal unipole aerial. Two independent methods are used to determine the electric field strength at the tip of the unipole. In one of these the voltage on the coaxial transmission line feeding the unipole is measured at a distance of three-quarters of a wavelength from the base of the unipole. In this way the current entering the base of the unipole can be found, and hence the electric field at the tip can be calculated. The other method makes use of a small microphone actuated by the attractive force of the electric field. When this method is used, the radio-frequency oscillator is square-wave modulated. The two methods give satisfactory agreement. In the breakdown experiments two unipoles of different base diameter were used. For each of these experimental values of the critical field strengths for onset of corona are compared with the values deduced from the diffusion theory of breakdown.

A Comparative Study of Dielectric Strength between SiR/EPDM and PP/EPDM Blends with Various Type of Nanofillers

2013 ◽  
Vol 832 ◽  
pp. 483-487 ◽  
Author(s):  
Noor Syazwani Mansor ◽  
Muhammad Safwan Hamzah ◽  
M. Kamarol ◽  
M. Mariatti
Keyword(s):  
Dielectric Properties ◽  
Field Strength ◽  
Electric Field ◽  
Comparative Study ◽  
Polymer Blends ◽  
Electric Field Strength ◽  
Silicone Rubber ◽  
Dielectric Strength ◽  
Nanocomposite Material ◽  
Average Value

This paper focused on studying the effect of addition of Al2O3, TiO2and BN nanofillers on dielectric strength of nanocomposite material. There are two types of polymer blends used in this project which are silicone rubber/EPDM and PP/EPDM blends. Nanocomposites samples was blended at 50:50 ratios and developed by compounding with and without 5 wt% concentration of Al2O3, TiO2, and BN. The results are compared based on performance in dielectric properties of each types of polymer blends. From the weibull probability plot, PP/EPDM blend with nanofillers shows the higher dielectic strength compared to the SiR/EPDM blends. From the average value of electric field strength, it was found that the value of electric field strengths for PP/EPDM/Al2O3,PP/EPDM, PP/EPDM/TiO2and PP/EPDM/BN were 42.76kV/mm, 38.44 kV/mm and 32.93 kV/mm respectively. The results for SiR/EPDM with addition of Al2O3, TiO2and BN are 37.43kV/mm 34.04kV/mm and 29.73kV/mm respectively. It was found that PP/EPDM blend gives better results for dielectric properties compared to SiR/EPDM blend.

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.

Weibull Distribution Function Based on an Empirical Mathematical Model for Inactivation of Escherichia coli by Pulsed Electric Fields

2003 ◽  
Vol 66 (6) ◽  
pp. 1007-1012 ◽  
Author(s):  
D. RODRIGO ◽  
G. V. BARBOSA-CÁNOVAS ◽  
A. MARTÍNEZ ◽  
M. RODRIGO
Keyword(s):  
Escherichia Coli ◽  
Mathematical Model ◽  
Distribution Function ◽  
Field Strength ◽  
Electric Field ◽  
Weibull Distribution ◽  
Electric Field Strength ◽  
Inactivation Kinetics ◽  
Carrot Juice ◽  
Weibull Distribution Function

The pulsed electric field inactivation kinetics of Escherichia coli suspended in orange juices with three different concentrations of carrot juice (0, 20, and 60%) was studied. Electric field strengths ranged from 25 to 40 kV/cm, and treatment times ranged from 40 to 340 μs. Experimental data were fitted to Bigelow, Hülsheger, and Weibull distribution functions, and the Weibull function provided the best fit (with the lowest mean square error). The dependency of each model's kinetic constant on electric field strength and carrot juice concentration was studied. A secondary model was developed to describe the relationship of Weibull parameters a and n to electric field strength and carrot juice concentration. An empirical mathematical model based on the Weibull distribution function, relating the natural logarithm of the survival fraction to treatment time, electric field strength, and carrot juice concentration, was developed. Parameters were estimated by a nonlinear regression. The results of this study indicate that the error rate for the model's predictions was 6.5% and that the model was suitable for describing E. coli inactivation.

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