Amplitude Of Electric Field Strength Research Articles

Droplets generation conducting during laser-plasma treating of metals in electric field

Evolution of plasma plume generation on the surface of metal irradiated by laser beam with the mean radiation flux density ~ 106 W/cm2 in the external electric field with different polarity and field strength from 0 to 106 V/m was experimentally investigated. It is shown that the mean size of metal droplets carried out from the irradiated zone of target becomes materially (in several times) smaller when of the external electric field strength amplitude grow, independently to its polarity. It is essential that the mentioned differences (at the considered parameters of laser radiation) are observed only at the initial stage of the laser plume development, because after the steam-plasma cloud reaches the electrode an electric breakdown (short-circuit) occurs, and the external field in the interelectrode gap disappears. Electric breakdown leads to the spasmodic increase of electron density and temperature of plasma and to effective absorption of laser radiation by plasma torch (shielding of the target). In consequence of shielding droplets generation happens only during electric field existence. This explains decrease by several times of the characteristic size of the target substance droplets in spite of short duration of electric field existence.

Nonlinear Interface Waves in a Trilayered Optical Structure with Different Layer Characteristics and Internal Self-Focusing

A model of a trilayered optical structure, the plane-parallel boundary of which possesses its own nonlinear properties, is considered. The inner layer with a finite thickness is an optically transparent medium with Kerr self-focusing nonlinearity, which is in contact with linear half-spaces from the outer surface that are characterized by refractive indices independent of the electric field strength amplitude. Refractive indices in the layer interfaces within infinitely small thicknesses are approximated by the dependence that includes Dirac’s delta function. It is shown that the mathematical formulation of the model boils down to a nonlinear Schrodinger equation with a nonlinear self-consistent potential. It is established that two types of nonlinear localized waves of the electric field strength perturbations can propagate along the layers in the considered trilayered structure. Dispersion relations of the interface waves that allow one to determine the propagation constant and decrements of their spatial attenuation in linear half-spaces as a function of the system parameters are derived. Conditions for localization of a luminous flux along the layer interfaces are analyzed in relation to the sign of the layer parameters. It is shown that the characteristic distance of the field localization linearly depends on the interface nonlinear response parameter. It is established that the characteristic localization distance is shortened in the case of a positive nonlinear response in comparison with the localization length when interfaces do not interact with the field and lengthened in the case of a negative nonlinear response.

Research on transient insulation numerical analysis method of circuit breaker in GIS under lightning impulse voltage

In order to reveal the process of insulation destruction of circuit breaker in GIS under lightning impulse voltage, a new method of transient insulation numerical analysis is described in this paper. A combination of the electromagnetic transient analysis method and optimised charge simulation method (CSM) was put forward to calculate and analyse the transient insulation characteristics of 550 kV circuit breaker in GIS under lightning impulse voltage. The results show that, within 0–15 μ, though the voltage of circuit breaker did not reach its peak, there is severe electric field distortion caused by sharp change of voltage with a high probability of circuit breaker insulation breakdown. In addition, as for the circuit breaker insulation structure optimisation design, it is advisable to restrain the change rate of electric field strength amplitude so as to reduce the probability of insulation breakdown, rather than simply verify insulation structure by using maxi-mum electric field strength as the voltage input parameters of the electrostatic field under the power frequency in accordance with the traditional insulation analysis method, with the purpose of ensuring the circuit breaker can operate safely and reliably for a long time.

Нелинейные интерфейсные волны в трехслойной оптической структуре с отличающимися характеристиками слоев и внутренней самофокусировкой

AbstractA model of a trilayered optical structure, the plane-parallel boundary of which possesses its own nonlinear properties, is considered. The inner layer with a finite thickness is an optically transparent medium with Kerr self-focusing nonlinearity, which is in contact with linear half-spaces from the outer surface that are characterized by refractive indices independent of the electric field strength amplitude. Refractive indices in the layer interfaces within infinitely small thicknesses are approximated by the dependence that includes Dirac’s delta function. It is shown that the mathematical formulation of the model boils down to a nonlinear Schrödinger equation with a nonlinear self-consistent potential. It is established that two types of nonlinear localized waves of the electric field strength perturbations can propagate along the layers in the considered trilayered structure. Dispersion relations of the interface waves that allow one to determine the propagation constant and decrements of their spatial attenuation in linear half-spaces as a function of the system parameters are derived. Conditions for localization of a luminous flux along the layer interfaces are analyzed in relation to the sign of the layer parameters. It is shown that the characteristic distance of the field localization linearly depends on the interface nonlinear response parameter. It is established that the characteristic localization distance is shortened in the case of a positive nonlinear response in comparison with the localization length when interfaces do not interact with the field and lengthened in the case of a negative nonlinear response.

On the Theory of Hydrogen Atom Ionization by Ultra‐Short Electromagnetic Pulses

AbstractAn investigation of the probability of hydrogen atom ionization by ultra‐short electromagnetic pulses is carried out in the frame of perturbation theory We consider the case when the electric field strength amplitude E0 in a pulse by two orders lower than characteristic atomic field strength Ea (Ea ≅ 5.1 · 109 V/cm). A detailed investigation of the dependence of the probabilities on the pulse duration was performed for Gaussian pulse shapes. In the case where the carrier frequency of the Gaussian pulse is larger than the atomic ionization potential, the probability goes to the standard limit of perturbation per unit time. At the same pulse durations, the probabilities for carrier frequencies less than the ionization potential go to zero. The frequency dependence of the ionization probability becomes equal to the standard threshold dependence with increasing pulse duration time. A comparison between the ionization effects caused by wavelet pulses without carrier frequency and Gaussian pulses with carrier frequency shows that the same ionization probability values are achieved when the pulse carrier frequency is detuned by about 20% from the ionization threshold. (© 2015 WILEY‐VCH Verlag GmbH & Co. KGaA, Weinheim)

Properties of the electron-positron plasma created from a vacuum in a strong laser field: Quasiparticle excitations

Solutions of a kinetic equation are investigated which describe, on a nonperturbative basis, the vacuum creation of quasiparticle electron-positron pairs due to a strong laser field. The dependence of the quasiparticle electron (positron) distribution function and the particle number density is explored in a wide range of the laser radiation parameters, i.e., the wavelength $\ensuremath{\lambda}$ and amplitude of electric field strength ${E}_{0}$. Three domains are found: the domain of vacuum polarization effects where the density of the ${e}^{\ensuremath{-}}{e}^{+}$ pairs is small (the ``calm valley'') and two accumulation domains in which the production rate of the ${e}^{\ensuremath{-}}{e}^{+}$ pairs is strongly increased and the ${e}^{\ensuremath{-}}{e}^{+}$ pair density can reach a significant value (the short wavelength domain and the strong field one). In particular, the obtained results point to a complicated short-distance electromagnetic structure of the physical vacuum in the domain of short wavelengths $\ensuremath{\lambda}\ensuremath{\lesssim}{\ensuremath{\lambda}}_{\mathrm{acc}}=\ensuremath{\pi}/m$. For moderately strong fields ${E}_{0}\ensuremath{\lesssim}{E}_{c}={m}^{2}/e$, the accumulation regime can be realized where a plasma with a high density of ${e}^{\ensuremath{-}}{e}^{+}$ quasiparticles can be achieved. In this domain of the field strengths and in the whole investigated range of wavelengths, an observation of the dynamical Schwinger effect can be facilitated.

Effect of electric field on the crystallization process of amorphous Fe86Zr7B6Cu1 alloy

The effect of an electric field on the crystallization process of amorphous alloys was studied by annealing amorphous Fe86Zr7B6Cu1 ribbons at 600°C for 1 h in the presence of an alternating current electric field. It is shown that the amplitude of the electric field strength has apparent effects on the grain size and volume fraction of the crystalline α-Fe phase. The grain size increases with an increase in the amplitude of the electric field strength. The volume fraction of the crystalline α-Fe phase increases with increasing amplitude of electric field strength from 0 to 104 V m−1 and then decreases with its further increase. The frequency of the electric field has no apparent effect on the crystallization process of amorphous ribbons. By analysing the mechanism of the effect of an electric field on the crystallization process of amorphous alloys, it is shown that the effect depends on the difference in conductivity between the new phase and the initial phase. When the conductivity of the precipitating phase is less than that of the remaining matrix, the use of an electric field can produce a nanocrystalline alloy with an ultrafine grain size.

Spontaneous excitation of magnetic fields and collapse dynamics in a Langmuir plasma

We discuss various aspects of the spontaneous generation of magnetic fields in a Langmuir plasma. We first of all show that the correct general expression for the ponderomotive force leads to the solenoidal current responsible for the magnetic-field generation. We derive the ponderomotive-force expression and also the magnetic-field generation equations from a two-time-scale two-fluid description. We also use a kinetic approach to derive the magnetic-field generation equations. We discuss the stability of monochromatic Langmuir waves and show that they are subject to both the ordinary modulational instability and to a magneto-modulational instability. We show that the coupled nonlinear equations describing the electric field strength amplitude, the plasma density, and the self-generated magnetic field can, under certain conditions, be reduced to a generalized cubic nonlinear Schrodinger equation. We finally show, by using a virial theorem, that the self-generated magnetic field does not stabilize the wave collapse.