The electron densities in the atmospheric pressure helium plasma were calculated by means of electron drift velocity and the jet velocity respectively. The electron velocity and jet velocity can be calculated by means of helium plasma jet current measured by a dielectric probe and plasma discharge current signal measured by voltage probes. The results show that the estimated electron densities of the helium plasma jet calculated from electron drift velocity and the jet velocity are in the order of 10 11 cm -3 and they increase with applied voltage. There is a little fluctuation in the value of the electron density along the jet axis of the plasma. This result is the same as the measured electron density in atmospheric pressure helium non-thermal plasma jet by using a Rogowski coil and a Langmuir probe. This is in one order lower than the electron density measured by microwave antenna. 相似文献
The drift motion of a 180° domain boundary in garnet ferrites with two nonequivalent sublattices is studied in an elastic stress field induced by an acoustic wave propagating in the domain boundary plane. The dependences of the drift velocity on the amplitude and polarization of the acoustic wave are obtained, and the drift motion conditions for a strip domain structure are determined. 相似文献
The velocity distribution function of passive-tracer particles in a gas flow on a closed boundary of a given spatial region is found for various relations between the regular drift and diffusion. An example of calculation of the velocity probability density on the boundary of a region comprising a source of particles is given.Translated from Izvestiya Vysshikh Uchebnykh Zavedenii, Radiofizika, Vol. 48, No. 1, pp. 86–93, January 2005. 相似文献
We study current-induced magnetization dynamics in a long thin ferromagnetic wire with a Dzyaloshinskii-Moriya interaction (DMI). We find a spiral domain wall configuration of the magnetization and obtain an analytical expression for the width of the domain wall as a function of the interaction strengths. Our findings show that above a certain value of DMI a domain wall configuration cannot exist in the wire. Below this value we determine the domain wall dynamics for small currents, and calculate the drift velocity of the domain wall along the wire. We show that the DMI suppresses the minimum value of current required to move the domain wall. Depending on its sign, the DMI increases or decreases the domain wall drift velocity. 相似文献
A dispersion relation for the ion-acoustic instability in a dc-discharge is derived. The dc electric field term in the linearized Vlasov-equation is not neglected, and the ion drift velocity is taken into account. Collisions of the electrons and ions with the neutrals are considered on the basis of a Davy-dov-collision term. The influence of the dc field and the ion drift leads to higher values of the spatial growth rates in the low frequency range and a shift of the maximum of the growth rates and the high frequency boundary of the unstable waves toward lower frequencies. The phase velocity diminishes, what is, above all, a result of the consideration of the ion drift velocity. 相似文献
Joule heat release during current flow through a fine wire connecting two bulk electrodes (two contacts) is considered. The irreversible heat release symmetric in the absence of electron–phonon coupling becomes asymmetric if this coupling is taken into account. The Joule heat release appears larger in that symmetric contact which lies along the carrier drift velocity. 相似文献
On the basis of a foregoing paper new theoretical results for the positive column at low pressure and strong ionization, especially for discharges in noble gas ion lasers, are given. The mean velocity vn0 of the neutral atoms reemitted from the wall is taken into account. The electric conductivity is calculated for an argon plasma. The formulas connecting the electron temperature, the mean neutral gas density, and the electric field strength are derived. The electron temperature, the axial electric field intensity, the degree of ionization, the axial electron drift velocity, the ion flux to the wall, and the force density causing the main part of gas pumping along the column are calculated as functions of the product of the mean current density and the tube radius, and of vn0 for argon. The axial drift velocity of the electrons is still smaller than the mean thermal electron velocity for high discharge currents, except at very low gas pressures. In general, the ion flux to the wall is not directly proportional to the discharge current. The factor for the determination of the charged particle density by means of probe measurements at the wall is discussed. The self-magnetic field affects the discharge only at high electron temperature, high degree of ionization, and relatively large tube radius, i.e. at high current density and low gas pressure in not too narrow discharge channels. 相似文献
The effect of a magnetic field on the ion drift in a weakly ionized gas under the combined action of the light-induced drift and light pressure is studied theoretically. It is shown that, under the action of light, a component of ion drift velocity transverse to the direction of propagation of radiation may appear in a weakly ionized gas upon the application of an external magnetic field. It is shown that the Lorentz force acting on ions in the magnetic field radically changes the dependence of the ion drift velocity on the radiation frequency detuning. It is predicted that the ion drift velocity component along the direction of radiation must reverse its sign upon an increase in the magnetic field and an anomalous light-induced drift may be observed. 相似文献
We study the unidirectional flow of a binary mixture of biased-random walkers on square lattice under a periodic boundary. The lattice-gas mixture consists of two types of walkers which have different biases (drift coefficients). The characteristics of unidirectional flow are clarified numerically. The mean velocity of slow particles in the binary mixture is enhanced higher than that in lattice-gas consisting of only slow particles. The mean velocity of slow particles shows a maximal value at an intermediate density. The dependence of velocity enhancement on both drift coefficient and mixture fraction is shown. Velocity enhancement is intensified with decreasing fraction of slow particles. Also, when the bias is lower, the velocity enhancement is higher. 相似文献
In this work, the expansion dynamics of a helium plasma jet in ambient air is examined. By using a fast imaging technique, the expansion of plasma jet from glass nozzle to air is captured which is in the form of plasma bullet propagating into the air. To understand the plasma bullet travel path from glass nozzle to plasma jet tip a drag force model is used. Moreover, the spatial variation of plasma density along the plasma jet length is estimated using drift velocity, plasma jet current and the cross-sectional area of the plasma jet. It is observed that the slight increase in plasma density is due to the combined effect of reduction of drift velocity, plasma jet current, and jet cross-sectional area. The obtained plasma density from glass nozzle to jet tip is in the range of (0.069-5.96) × 1012 cm−3. The above parameters can be of the essence in biological and industrial applications. 相似文献
We revisit the theory of the transients in low-temperature extrinsic photoconductors, with emphasis on the initial fast component
response. Application of a photon-generation step launches a traveling zone boundary between part of the device where, in
the short term, a quasi-equilibrium has been reached and a part where the carrier concentration is still growing. As the boundary
passes, the exponentially slowing growth of carriers is abruptly terminated. The time to reach this quasi-equilibrium depends
on the sample length and the carrier drift velocity rather than on the carrier lifetime. We note restricting errors in earlier
analyses and produce an improved formula for the subsequent slow fraction of the total current change by including carrier
diffusion. Comparison of numerical and analytical results suggests that measurement of the fast or slow fraction of the response
can provide a highly accurate measure of the mobility-lifetime (μτ) product.
Received: 16 October 2000 / Accepted: 31 October 2000 / Published online: 3 April 2001 相似文献
Electromagnetic transport measurements were combined with high-resolution electron microscopy observations to study the relation between structure and local critical currents in YBa2Cu3O7–x (YBCO) Josephson junctions. The spatial variation of the critical current J(x) along the length of the boundary for interface engineered Josephson junctions and bicrystal grain boundary Josephson junctions was determined using a phase retrieval algorithm. The current distribution solutions were found to be highly uniform along the length of interface engineered junctions in contrast to solutions for grain boundary junctions. The latter showed significant spatial oscillations in the critical current as well as areas along the boundary that carried no current. Microstructural evaluation of interface engineered junctions fabricated using identical processing parameters to the junctions used for transport measurements suggest that the uniform current distribution is controlled by a highly uniform barrier layer formed between the superconducting electrodes. Microstructural evaluation of grain boundary junctions similar to the junctions used for transport measurements show considerable variations of the grain boundary structure within a single junction. 相似文献
Measurements of Thomson scattering in a Tokamak with a component of the scattering vector k along the current direction, give scattered spectra with a red or a blue shift according to the direction of the current. Assuming a displaced Maxwellian electron distribution function it has been possible to determine the local electron drift velocity and hence the local current density. An increase in time of current density on axis, followed by a sudden decrease has been observed: this is probably due to the relaxation following a thermal instability. 相似文献
In this Letter, the influence of the "Coriolis drift" on small scale instabilities in toroidal plasmas is shown to generate a toroidal momentum pinch velocity. Such a pinch results because the Coriolis drift generates a coupling between the density and temperature perturbations on the one hand and the perturbed parallel flow velocity on the other. A simple fluid model is used to highlight the physics mechanism and gyro-kinetic calculations are performed to accurately assess the magnitude of the pinch. The derived pinch velocity leads to a radial gradient of the toroidal velocity profile even in the absence of a torque on the plasma and is predicted to generate a peaking of the toroidal velocity profile similar to the peaking of the density profile. Finally, the pinch also affects the interpretation of current experiments. 相似文献
A mechanism of amplification of surface plasmon polaritons due to the transfer of electromagnetic energy from a drift current wave into a far‐infrared surface wave propagating along a semiconductor‐dielectric boundary in waveguide geometry is proposed. A necessary condition of the interaction of these waves is phase matching condition, i. e., when the phase velocity of the surface wave approaches the drift velocity of charge carriers. It is shown that in the spectral region of the surface plasmon polariton slowing‐down its amplification coefficient can reach values substantially exceeding the ohmic loss coefficient of the surface wave in the structure.