Time-resolved Emission Spectroscopy Characteristics Of Dielectric Barrier Discharges In Atmospheric-pressure Noble Gases

Dielectric barrier discharge （DBD） has various promising applications in industry.However, there still lacks reasonable explanations on the characteristics of DBD, and furtherstudies on the DBD plasmas are required. In this thesis, using electrical parametersmeasurements, ICCD camera and grating spectrometer, the discharging mechanism, Penningionization in discharge and the variations of compositions and parameters of plasmas inatmospheric-pressure DBD in Helium, Argon and Neon were studied.The gas voltage between electrodes during discharge was measured, and differencesbetween calculated and directly-measured Lissajous figures were discussed. On this base,variations of equivalent capacitance and space charges were analyzed. It was concluded thatthe discharge is affected by the variation rates of applied voltage and wall charges on thesurface of electrodes.Both short-exposure-time and time-resolved spectra under different background airpressures in APGD in helium were studied with ICCD camera and grating spectrometer. Thevariations of typical spectral lines over time have been analyzed. In helium with a lowconcentration of N2（4.0Pa background air pressure）, the emission of He at706.5nm isdominant and appears500ns earlier than N₂⁺first negative bands, indicating low reactionrates of Penning ionization and charge transfer in the initial stage. When helium contains ahigher concentration of N2molecules （20Pa background air pressure）, the N₂⁺first negativebands become the most intense, and emissions from He, N₂⁺and O exhibit similar behavior asthey increase. During the decay, it is Penning ionization caused by long-lifetime Hemetastables rather than charge transfer reaction that leads to the long decay of N₂⁺emissions.In multi-pulse discharge, the emissions of N₂⁺first negative bands keep certain intensity,while spectral lines of He706.5nm and O777.4nm cannot be detected. Since new ions andelectrons are generated in Penning ionization, electric field in the discharge space keeps beingdistorted, and the uniform electric field required in Townsend discharge no longer exists. Sothe discharge does not extinguish but keeps weak glow discharge between adjacent pulses,and further keeps that mode during the whole process of next pulse.The electrical characteristics, emission spectra and discharge power characteristics of atmospheric-pressure Argon and Neon plasmas were also studied. Several discharge modesincluding glow, pattern, column and filaments were observed as Argon has high breakdownfield strength and discharge can easily transfer to stream. On the contrary, Neon has only oneglow discharge mode since it has much lower breakdown field strength. Besides, bothPenning ionization and the intensities of spectral lines are very weak as direct impactdominates in Argon. And all the spectral lines develop synchronously with discharge current.However, since the energy level of Neon metastables is lower than the excitation energy ofN₂⁺, the emissions of N₂⁺first negative bands are not observed. Because the Neon gas used inthe study has high purity, the emissions from N2second positive bands cannot be detected.