Xiaoou Wang

Broadband microwave characteristics of a novel coaxial gridded hollow cathode argon plasma

The interaction between microwave and large area plasma is crucially important for space communication. Gas pressure, input power, and plasma volume are critical to both the microwave electromagnetic wave phase shift and electron density. This paper presents a novel type of large coaxial gridded hollow cathode plasma having a 50 cm diameter and a 40 cm thickness. Microwave characteristics are studied using a microwave measurement system that includes two broadband antennae in the range from 2 GHz to 18 GHz. The phase shift under varying gas pressure and input power is shown. In addition, the electron density ne, which varies from 1.2 × 10(16) m(-3) to 8.7 × 10(16) m(-3) under different discharge conditions, is diagnosed by the microwave system. The measured results accord well with those acquired by Langmuir Probe measurement and show that the microwave properties in the large volume hollow cathode discharge significantly depend on the input power and gas pressure.

Absolute continuum intensity diagnostics of a novel large coaxial gridded hollow cathode argon plasma

This paper reports a novel coaxial gridded hollow discharge during operation at low pressure (20u2009Pa–80u2009Pa) in an argon atmosphere. A homogeneous hollow discharge was observed under different conditions, and the excitation mechanism and the discharge parameters for the hollow cathode plasma were examined at length. An optical emission spectrometry (OES) method, with a special focus on absolute continuum intensity method, was employed to measure the plasma parameters. The Langmuir probe measurement (LPM) was used to verify the OES results. Both provided electron density values (ne) in the order of 1016u2009m−3 for different plasma settings. Taken together, the results show that the OES method is an effective approach to diagnosing the similar plasma, especially when the LPM is hardly operated.

Influences of Microscopic Parameters of Tripod Like Chiral Molecules on the First Zero-Frequency Hyperpolarizabilities

In this study, we derived explicitly the zero-frequency first hyperpolarizabilities of tripod like chiral molecules based on a three-coupled-oscillator model and determined the relations of the zero-frequency first hyperpolarizabilities with molecular structure, molecular chirality and the wavelength of incident light. Furthermore, we also simulated numerically the influences of microscopic parameters of chiral molecules and the wavelength of incident light on the first zero-frequency hyperpolarizabilities. We observed fact that the influences of microscopic parameters of chiral molecules on zero-frequency first hyperpolarizabilities is different by using different chiral molecular microscopic parameters such as bond angle and molecular chirality. Furthermore, the influences of microscopic molecular parameters on the first zero-frequency hyperpolarizabilities can also help to comprehend nonlinear optical mechanism of chiral molecules.

A Photoexcited Broadband Absorption Based on Au Nano Cross Elliptical Disks Structure with Polarization-Insensitive and Wide-Angle for Visible Light

We present the design and numerical simulations of a polarization-insensitive and wide-angle photoexcited broadband metamaterial absorption in the visible region base on Au nano cross elliptical disks structure. The Au nano cross elliptical disks structure comprises a periodic array of metal-dielectric multilayered structure and a no transmission metallic functional layer on the bottom. Utilizing 3D finite difference time domain (FDTD) algorithm, the hybrid surface plasmon and the polarization-insensitive absorption of above 90xa0% for a wide range of incident angles of 40° are observed in the whole visible light (3.8–7.8u2009×u20091014xa0Hz).

Generation of banded chorus by a two-component energetic electron distribution in an inhomogeneous magnetic field

The generation of banded chorus by a two-component energetic electron distribution in a mirror-like inhomogeneous magnetic field is investigated in this work by a 1D hybrid code DAWN. A previous study by Liu et al. [Geophys. Res. Lett. 38, L14108 (2011)] suggested that banded chorus waves can be independently generated by two energetic electron populations. In this work, we first conduct a series of simulations to confirm that the starting frequency of chorus elements is close to the frequency of maximum linear growth rate. With carefully chosen simulation parameters, we then successfully generate banded chorus with a gap near half the electron gyrofrequency. By expanding the parameter range, however, we demonstrate that the gap can be located at frequencies other than the half electron gyrofrequency. We conclude that though the previous mechanism proposed by Liu et al. [Geophys. Res. Lett. 38, L14108 (2011)] can explain the relative independence of upper band and lower band chorus, further work is needed...

Broadband microwave propagation in a novel large volume glow discharge argon plasma

The broadband microwave propagating characteristics of a novel, large volume, glow-discharge argon plasma is reported in this paper. A large volume, glow-discharge argon plasma was designed and the basic plasma parameters were determined using an Impedans Ltd. Langmuir probe under a variety of conditions. The transmission attenuation was recorded by using S parameters of a vector network analyzer with the frequency range from 2GHz to 18GHz and a propagation model was established using the Z transform FDTD method for simulating the attenuation of microwave. The effects of both the gas pressure and input power on the EM wave propagation are analyzed. The results showed that the theoretical and experimental results of transmission attenuation were in good agreement. Moreover, the electron density ne and the effective collision rate vc were found to play important roles in the propagation of microwave.