The parameters of electron avalanches and the runaway of electrons in strong electric fields

2008 ◽  
Vol 46 (4) ◽  
pp. 440-448 ◽  
Author(s):  
K. N. Ul’yanov
Keyword(s):  
Electric Fields ◽  
Strong Electric Fields ◽  
Electron Avalanches

Numerical modeling of cathode-directed streamers branching in strong electric fields

2016 ◽  
Author(s):  
Белогловский ◽  
Andrey Beloglovskiy ◽  
Федорова ◽  
A. Fedorova
Keyword(s):  
Numerical Modeling ◽  
Numerical Model ◽  
Electric Fields ◽  
Strong Field ◽  
Strong Electric Field ◽  
Three Dimensional ◽  
Strong Electric Fields ◽  
Electron Avalanches ◽  
Discharge Gap ◽  
Positive Streamer

A research of conditions of the branching of positive streamer in air in a strong electric field by the use a three-dimensional numerical model is presented. This model is based on the assumption that the development of large electron avalanches in the strong field in front of the streamer head leads to branching. Tendency for branching has been observed, if the ratio of the diameters of the streamer heads to the distance between them is not greater than 0.55. If this ratio is more than 0,55, merger of originally formed streamer heads has been observed, and then only one streamer develops in the discharge gap.

Die Statistik der Elektronenlawinen in elektronegativen Gasen, bei hohen Feldstärken und bei großer Gasverstärkung

1961 ◽  
Vol 16 (3) ◽  
pp. 253-261 ◽  
Author(s):  
Werner Legler
Keyword(s):  
Exponential Distribution ◽  
Electric Fields ◽  
Previous History ◽  
Ionization Probability ◽  
Mean Value ◽  
Simplifying Assumptions ◽  
History Of ◽  
Strong Electric Fields ◽  
Electron Avalanches ◽  
The Individual

The statistical distribution of the carrier number of single electron avalanches in a TOWNSEND discharge is described by v(n) = 1/n·exp (—n/n̄) if one introduces some simplifying assumptions. These assumptions are violated in the case of electronegative gases, in strong electric fields, and in the case of large gas-amplification. In electronegative gases only a part of the primary electrons form observable electron avalanches. These are still subject to an exponential distribution but with an increased mean value. In strong electric fields the ionization probability depends on the previous history of the individual electrons. This leads to a distribution with a marked maximum and a reduced dispersion. In a first approximation the form of the distribution is determined by the quotient E/α: Ui. In the case of large gas-amplification the further development of the avalanche is influenced by the space charge and one gets a modified exponential distribution. The calculated distributions agree well with the experiments of other authors.

Calculation of the probability of optical transitions in strong electric fields

2000 ◽  
Vol 91 (5) ◽  
pp. 945-951 ◽  
Author(s):  
S. V. Bulyarskii ◽  
N. S. Grushko ◽  
A. V. Zhukov
Keyword(s):  
Electric Fields ◽  
Optical Transitions ◽  
Strong Electric Fields

Electrohydrodynamic rotation of drops at large electric Reynolds numbers

2016 ◽  
Vol 788 ◽  
Author(s):  
Ehud Yariv ◽  
Itzchak Frankel
Keyword(s):  
Electric Fields ◽  
Numerical Solutions ◽  
Fluid Velocity ◽  
Reynolds Numbers ◽  
Mirror Image ◽  
Liquid Drops ◽  
Weakly Conducting ◽  
Strong Electric Fields ◽  
Quincke Rotation ◽  
Asymmetric Solution

When subject to sufficiently strong electric fields, particles and drops suspended in a weakly conducting liquid exhibit spontaneous rotary motion. This so-called Quincke rotation is a fascinating example of nonlinear symmetry-breaking phenomena. To illuminate the rotation of liquid drops we here analyse the asymptotic limit of large electric Reynolds numbers, $\mathit{Re}\gg 1$, within the framework of a two-dimensional Taylor–Melcher electrohydrodynamic model. A non-trivial dominant balance in this singular limit results in both the fluid velocity and surface-charge density scaling as $\mathit{Re}^{-1/2}$. The flow is governed by a self-contained nonlinear boundary-value problem that does not admit a continuous fore–aft symmetric solution, thus necessitating drop rotation. Furthermore, thermodynamic arguments reveal that a fore–aft asymmetric solution exists only when charge relaxation within the suspending liquid is faster than that in the drop. The flow problem possesses both mirror-image (with respect to the direction of the external field) and flow-reversal symmetries; it is transformed into a universal one, independent of the ratios of electric conductivities and dielectric permittivities in the respective drop phase and suspending liquid phase. The rescaled angular velocity is found to depend weakly upon the viscosity ratio. The corresponding numerical solutions of the exact equations indeed collapse at large $\mathit{Re}$ upon the asymptotically calculated universal solution.

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