Jiang Zhong-He

Electromagnetic Wave Attenuation in Atmospheric Pressure Plasmas

The properties of electromagnetic waves in atmospheric pressure plasmas are investigated with the Lorentz model. The effects of the electromagnetic wave frequency, plasma density, and the electron-neutral collision frequency on the attenuation of electromagnetic waves are discussed. The numerical results indicate that the wave attenuation is stronger at the region of the longer wavelength and at the higher plasma density.

Interaction of Electromagnetic Waves with Two-Dimensional Metal Covered with Radar Absorbing Material and Plasma

A two-dimensional metal model is established to investigate the stealth mechanisms of radar absorbing material (RAM) and plasma when they cover the model together. Using the finite-difference time-domain (FDTD) method, the interaction of electromagnetic (EM) waves with the model can be studied. In this paper, three covering cases are considered: a. RAM or plasma covering the metal solely; b. RAM and plasma covering the metal, while plasma is placed outside; c. RAM and plasma covering the metal, while RAM is placed outside. The calculated results show that the covering order has a great influence on the absorption of EM waves. Compared to case a, case b has an advantage in the absorption of relatively high-frequency EM waves (HFWs), whereas case c has an advantage in the absorption of relatively low-frequency EM waves (LFWs). Through the optimization of the parameters of both plasma and RAM, it is hopeful to obtain a broad absorption band by RAM and plasma covering. Near-field attenuation rate and far-field radar cross section (RCS) are employed to compare the different cases.

Propagation of Electromagnetic TM (S-Polarization) Mode in Two-Dimensional Atmospheric Plasma

The finite-difference-time-domain (FDTD) method is applied to simulate the two-dimensional propagation of electromagnetic TM (S-polarization) mode in atmospheric plasma and in metal layer for strong electron-neutral collisions. Dependence of the wave attenuation on both plasma parameters and incident wave angle are obtained. It is indicated that for a given electron density profile the attenuation depends strongly on the incident angle, the wave frequency, the width of plasma layer, and the collision frequency between electrons and neutrals.

Finite-Difference Time-Domain Analysis of Wave Propagation in a Thin Plasma Layer

The propagation property of an electromagnetic wave in a thin plasma layer at high pressure is investigated with the finite-difference time-domain method. The effects of the non-uniformity of plasma distribution, and the frequency of incident wave on the propagation property of the electromagnetic wave are discussed. Numerical results indicate that the phase shift and the reflectivity of wave are sensitive to plasma density distribution, and reflectivity is lower at the middle band of frequency for different plasma distributions.

Effects of ambient pressure on bubble characteristics

The effects of the ambient pressure Pambient on the bubble characteristics of pulsed discharge in water are investigated. The simulation results show that, when Pambient increases from 1 atm to 100 atm, the bubble radius R decreases from 4 cm to 7 mm, and its pulsation period decreases from 8 ms to 0.2 ms. The results also show that the peak pressure of the first shock wave is independent of Pambient, but the peak pressure of the second shock wave caused by the bubble re-expansion decreases when Pambient increases. On the other hand, the larger the ambient pressure, the larger the peak pressure of the plasma in the bubble, while the plasma temperature is independent of Pambient.

Three-Dimensional Numerical Simulation of Surface-Wave Plasma Source

A three-dimensional model of a surface-wave plasma (SWP) source is built numerically using the finite-difference time-domain (FDTD) method to investigate the structure of the surface wave propagation along the plasma-dielectric interface and the distributions of electromagnetic fields in the whole system. A good-performance excitation source technique for the waveguide which is pivotal to the simulation is presented. The technique can avoid the dc distortions of magnetic fields caused by the forcing electric wall. An example of simulation is given to confirm the existence of the surface waves. The simulation also shows that the code developed is a useful tool in the computer-aided design of the antenna of the SWP source.

Calculation and Analysis of Magnetic Field Pattern for TEXT-U Equipment

In this paper, the toroidal field of a tokamak produced by separate coils has been calculated from the basic electrodynamic theory. As an example, the toroidal magnetic field (R) in TEXT-U tokamak is plotted, and the curve is fitted well to the analysis formula (R) = 0R0/R with a precision of several percents.

Effect of Air Gap on Uniformity of Large-Scale Surface-Wave Plasma

The effect of air gap on the uniformity of large-scale surface-wave plasma (SWP) in a rectangular chamber device is studied by using three-dimensional numerical analyses based on the finite difference time-domain (FDTD) approximation to Maxwells equations and plasma fluid model. The spatial distributions of surface wave excited by slot-antenna array and the plasma parameters such as electron density and temperature are presented. For different air gap thicknesses, the results show that the existence of air gap would severely weaken the excitations of the surface wave and thereby the SWP. Thus the air gap should be eliminated completely in the design of the SWP source, which is opposite to the former research results.

Compressibility Effects on the Rayleigh–Taylor Instability Growth Rates

Effects of two compressibility parameters, i.e. the ratio of specific heats and the equilibrium pressure at the interface, on the Rayleigh–Taylor instability (RTI) growth rates are studied under the same initial conditions, which include the mass, pressure profile, and density profile of the two superposed fluids. The results obtained reconcile the stabilizing and destabilizing effects of compressibility reported in the literature. The influences of the ratio of specific heats on the RTI growth rates are not only stabilized but also destabilized. The effects of the equilibrium pressure at the interface on the growth rates are destabilized.

Absolute and Convective Instabilities of Two-Plasmon Decay in an Inhomogeneous Magnetized Plasma*

Three-wave resonant parametric decay instability of extraordinary wave decay into two upper hybrid waves in an inhomogeneous plasma is studied theoretically. Analytical expressions of the local absolute growth rate, convective amplification factor and threshold intensity are obtained. The calculated results show that the effects of magnetic field and ky (ky is the component of the wavenumber of upper hybrid wave perpendicular to pump wave k0) on the growth rate, amplification factor and threshold intensity are extremely dependent on their strength. The absolute growth rate and convective amplification factor increase with the plasma density while the threshold decreases. Moreover, the expression indicates that the inhomogeneity scale length of density and linear damping will reduce the convective amplification factor.