Zhaoquan Chen

Filamentary streamer discharges in argon at atmospheric pressure excited by surface plasmon polaritons.

This paper describes a microwave plasma jet in an argon atmosphere capable of generating filamentary streamer discharges within the entire quartz tube excited by surface waves of surface plasmon polaritons (SPPs) located in the tube. Several discharge streamers are immediately produced at the end of the copper wire when incident power reaches 20 W. From simulations, the wavelength of the surface wave was found to be approximately 5.7 cm. Although the developing streamers induce E-field enhancements favoring discharging, more streamer bifurcations requiring additional energy to maintain discharging diminish the resonant enhanced E-field. The underlying mechanism of the proposed plasma jet is resonant excitation of SPPs and its interaction with plasmas.

Polarization-Insensitive Triple-Band Microwave Metamaterial Absorber Based on Rotated Square Rings

An ultra-thin triple-band metamaterial absorber (MA) is proposed in the microwave region, which is composed of a periodic array of three rotated square rings (RSRs) and a continuous metal fllm separated by only 1mm dielectric substrate. The fabricated MA exhibits three experimental absorption peaks at 4.88GHz, 7.88GHz, and 11.32GHz with the corresponding absorption rates of 98.8%, 96.5%, and 95.9%, which shows an excellent agreement with the simulated results. The triple-band MA is polarization-insensitive at the normal incidence. Finally, the multi-re∞ection interference theory is introduced to interpretate the absorption mechanism. The calculated absorption rates of the improved unit cell for the strongly coupled MA coincide well with the simulated results at wide angles of incidence for both transverse electric (TE) and transverse magnetic (TM) waves.

More Efficient Microwave Argon Plasma Jet With a Symmetric Hairpin Copper Wire at Atmospheric Pressure

In this paper, 2.45-GHz microwave argon plasma jets at atmospheric gas pressure are generated at the end of quartz tube (with an inner radius of 2 mm). With the applied power of 50 W and the different patterns of exciter, the lengths of plasma jet plume out of the end of quartz tube, about 5, 15, and 25 mm, respectively, are obtained. Moreover, the simulated result suggests that the efficient plasma jet with a symmetric hairpin copper wire is attributed to the enhanced electric field of local surface plasmon polaritons.

Longer Microwave Plasma Jet With Different Discharge Performances Originated by Plasma–Surface Interactions

With an input power of 50 W and a gas pressure of 100 Pa, 2.5 (without metal wire) and 10.5 cm (with a copper wire) long microwave air plasma jets are generated, respectively. When 95% Ar + 5% O2 is instead of air, the length of the plasma jet is stretched to 15 cm. Furthermore, the length of plasma plume is affected differently by adding the processed materials. These different discharge performances originate from the effect of plasma-surface interactions.

Study on Argon Plasma Jets at Atmospheric Pressure in Ambient Air Excited by Surface Waves

A novel method to produce strong and effective argon plasma jets in air is reported. By adjusting the structure and setting the location of a copper wire in the quartz tube, an intensive jet composed of two jets about 2.4 cm is produced with microwave power of 50 W. The microwave frequency is 2.45 GHz. Four twisty plasma jets about 2.0 cm for argon discharge are generated in four tubes at incident power of 120 W. A plasma ball of air discharge about 0.5 cm in radii is generated in the tube at the power of 100 W. The simulated distribution of electric field in the tube with a folded copper wire is consistent with the prediction of surface plasmon polaritons. Spectral diagnosis of the plasma jets is also discussed in this paper.

Slot-array antenna devising for surface microwave discharge of surface plasmon polaritons

The production of surface microwave discharge is verified as a stable discharge excited by surface electromagnetic waves which is carried by surface plasmon polaritons. In order to achieve the purpose of coupling microwave energy efficiently and surface-wave discharge stably, in addition based on the dipole near-field radiation theory, we design the subwavelength diffraction grating. Moreover, the near-field radiation electric field distribution is studied by special proposed computation method and further the aim of design is achieved.

Donut shape plasma jet plumes generated by microwave pulses even without air mole fractions

It is well known that the plasma jets driven by lower frequency voltages or pulsed DC power supply normally present with donut shaped cross sections, especially at where the diffused air mole fractions are less than 0.01. Thence, it is interesting to further study whether the donut shape is still in truth for the pulsed microwave plasma jet or not. In this letter, the cross sectional structures of atmospheric pressure plasma jet plumes driven by pulsed microwaves have been experimented on a cylindrical coaxial transmission line resonator. The plasma jet plumes demonstrate particular characteristics, like argon plasma with a donut shape but helium plasma with an uniform lighten cross section, despite whether the air mole fraction exists or not. For argon discharge, the fast images show that the donut shaped cross section only occurs at the end of each microwave pulses. In combination with helium discharge, the cross sectional patterns are immediately determined by the dominant ionization front of the plasm...

A New Remote Control Microwave Plasma Jet Excited by Surface Waves

A 2.45-GHz microwave plasma jet (MPJ) is designed based on the excitation of surface plasmon polaritons located in the discharge tube. The unique structure of internal metal antenna with an adjusting screw-pitch gauge is convenient to control plasma discharge at different locations for various gases (Ar, N2, O2, and so on) MPJ can be operated at wide pressure range with low incident power. R`egulating the position of the metal antenna and the flow rate, the longest plasma jet of 23 cm is produced at 100 Pa with the operating power of 30 W. As for high pressure, a plasma jet with a length of 7.5 cm is generated 50-cm away from the hole of the waveguide when incident power reaches 50 W. Field analysis is performed using the traditional software, plasma density, electron temperature, and the discharge components are diagnosed analyzed by the Langmuir double probe and spectrograph, respectively. This kind of plasma jet can be achieved for discharge at the desired positions, so it is suitable for the special industrial applications, such as ignition and recombustion for a certain distance.

Investigation of the Arrayed Dielectric Barrier Discharge Reactor for PM2.5 Removal in Air

Low-temperature plasma treatment is a promising technology for particulate matter (PM). In this paper, the arrayed dielectric barrier discharge (DBD) plasma reactor for PM2.5 removal is investigated at atmospheric pressure. In order to reveal the interaction between experimental findings and simulation results, the equivalent electrical circuit is used. The electrical model is implemented on the PSIM software. To calculate the capacitance of the arrayed DBD reactor, the capacitor expressions are developed. Considering the experimental elements, such as plasma-generated configuration and the power source, a topological equivalent circuit is given. Finally, the simulation results are compared with the experimental ones, and they agree well. In addition, the designed DBD reactor was used to investigate PM2.5 removal. PM2.5 removal after 4 min of plasma treatment found to be about 53.8%.

Study on DC-Driven Air Cold Plasma Brushes Generated Without Airflow Supplement

In this paper, 30-mm-wide cold atmospheric-pressure air plasma brushes are reported. The brushes driven by a direct current power supply are capable of generating air plasma glows with no noble gas addition and no airflow supplement. There is no risk of glow-to-arc transitions, and the plasma glow appears uniform no matter what kinds of material are being processed. The air plasma glow can be scaled up by using the plasma brush arrays. About 30mm × 30mm × 5mm (W, H, and L) homogeneous air plasma glow is generated by merging seven-brush arrays. Current measurements show that the single-brush discharge appears periodically pulsed, while the brush array discharge actually presents either pulsed with about array-number-times frequency of the single one. A further analysis indicates that the charge particles trapped along the dielectric surface may be responsible for the discharges.