Xia Guangqing

Electromagnetic interaction between local surface plasmon polaritons and an atmospheric surface wave plasma jet

We analyze the electromagnetic interaction between local surface plasmon polaritons (SPPs) and an atmospheric surface wave plasma jet (ASWPJ) in combination with our designed discharge device. Before discharge, the excitation of the SPPs and the spatial distribution of the enhanced electric field are analyzed. During discharge, the critical breakdown electric field of the gases at atmospheric gas pressure and the surface wave of the SPPs converted into electron plasma waves at resonant points are studied. After discharge, the ionization development process of the ASWPJ is simulated using a two-dimensional fluid model. Our results suggest that the local enhanced electric field of SPPs is merely the precondition of gas breakdown, and the key mechanism in maintaining the discharge development of a low-power ASWPJ is the wave-mode conversion of the local enhanced electric field at the resonant point.

Pulsed microwave-driven argon plasma jet with distinctive plume patterns resonantly excited by surface plasmon polaritons*

Atmospheric lower-power pulsed microwave argon cold plasma jets are obtained by using coaxial transmission line resonators in ambient air. The plasma jet plumes are generated at the end of a metal wire placed in the middle of the dielectric tubes. The electromagnetic model analyses and simulation results suggest that the discharges are excited resonantly by the enhanced electric field of surface plasmon polaritons. Moreover, for conquering the defect of atmospheric argon filamentation discharges excited by 2.45-GHz of continued microwave, the distinctive patterns of the plasma jet plumes can be maintained by applying different gas flow rates of argon gas, frequencies of pulsed modulator, duty cycles of pulsed microwave, peak values of input microwave power, and even by using different materials of dielectric tubes. In addition, the emission spectrum, the plume temperature, and other plasma parameters are measured, which shows that the proposed pulsed microwave plasma jets can be adjusted for plasma biomedical applications.

Numerical Simulation on the Production Mechanism of Surface-Wave Plasmas Sustained along a Metal Rod

For interpreting the production mechanism of surface-wave plasmas sustained along a metal rod, electromagnetic simulation on the electromagnetic field distributions and particle-in-cell/Monte Carlo collision (PIC/MCC) simulation of the ionization process are present. The results show that the enhanced electric field of surface plasmon polaritons (SPPs) can be excited in the ion sheath layer between the negative-voltage metal rod and the surface-wave plasmas, which is responsible for maintaining the plasma discharge. Moreover, the spatio-temporal evolutions of plasma density and electric fields are simulated by the PIC/MCC model. It is further suggested that the expanded ion sheath layer can extend the length of plasma domain by increasing the plasma absorbed energy from SPPs.

A 30 mm Wide DC-Driven Brush-Shaped Cold Air Plasma Without Airflow Supplement

This paper reports a cold atmospheric pressure DC-driven air plasma brush. Three stainless steel needles are symmetrically mounted on a slot shaped PVC slab to act as the electrodes. The brush driven by a direct current (DC) power supply can generate an air plasma glow up to 30 mm wide with no inert gas addition and no air flow supplement. The plasma glow appears uniform no matter what kinds of material are processed. The measured current and the simulated current all show that each pulsed discharge including two peaks always occurs for different gaps between electrodes. Emission spectra measurement result shows that the obtained rotational temperatures are 300 K and the vibrational temperatures are 2250 K. Some reactive species are presented in the plasma glow, which suggest that the proposed plasma brush is beneficial to practical applications.

Observation of Hot Electrons in Surface-Wave Plasmas Excited by Surface Plasmon Polaritons

The electron energy distribution functions (EEDFs) are studied in the planar-type surface-wave plasma (SWP) caused by resonant excitation of surface plasmon polaritons (SPPs) using a single cylindrical probe. Sustained plasma characteristics can be considered as a bi-Maxwellian EEDF, which correspond to a superposition of the bulk low-temperature electron and the high-energy electron beam-like part. The beam component energy is pronounced at about 10eV but the bulk part is lower than 3.5eV. The hot electrons included in the proposed plasmas play a significant role in plasma heating and further affect the discharge chemistry.

Character Diagnosis for Surface-Wave Plasmas Excited by Surface Plasmon Polaritons

The plasma parameters of planar-type surface-wave plasmas (SWPs) are diagnosed based on the resonant excitation of surface plasmon polaritons (SPPs). The plasma parameter distributions are obtained by changing the discharge conditions of gas pressure and incident power. The measured experimental results show that the plasma near the heating layer is excited by surface waves of SPPs while the plasma located downstream originates from diffusion Moreover, the influence of high-frequency oscillations plays a significant role in producing the proposed SWPs with bi-Maxwellian electron energy distributions.

Principle prototype design for ground experiment of helicon plasma thruster

Helicon plasma thruster is a novel electromagnetic thruster, which is based on the currentless double layer effect of the helicon plasma existing in the diverging magnetic field, accelerates the ions to form ion beam flow at a high speed, thus produces thrust. The key components of the HPT include a radio frequency antenna with specific structure and a magnetic field with certain type. This paper firstly summarizes the performance characteristics of the HPT, then gives the principle prototype design scheme for ground experiment of helicon plasma thruster concretely. The conclusion can provide the theoretical basis and reference for the further experimental study and the optimization design of the thruster.