Research On The Ultraviolet Features And Multi-spectral Imaging Technology Of High Voltage Air Discharge

As we know, high voltage gas discharge plasma is a hot research topic in the world. Through the method of gas discharge to generate plasma, it can be used in the field of lighting, nanotechnology, biomedical, environmental protection, surface material and so on. But, air arc / corona in a normal air pressure can cause power loss and sustained damage to electric power system and high voltage electrical equipment. So air discharge plasma target in atmospheric pressure is needed to carry out research on its parameters and characteristics, which is very necessary.The main research contents of this dissertation is the view of atmospheric pressure high voltage air discharge plasma target. We analyze the principle of the generation of air discharge, provide an overview of the Townsend theory and the streamer theory, and also describe the discharge process under atmospheric pressure is consistent, from simple Townsend discharge air breakdown to stable self-sustained discharge type rapidly. Through spectrum detection system for targets, we have done the UV spectrum experiment, completed the measurement between 200nm-1000 nm and the analysis, and found that air discharge plasma(arc / corona) spectral distribution mainly concentrated in the 200nm-400 nm ultraviolet band, and its emission spectral characteristic peaks is closely related to Nitrogen ions excited state emission spectrum peaks. At the same time, we have carried out the simulation of discharge plasma, through three different structures, based on three basic physical principle models, and get the micro process of atmospheric pressure discharge, which includes Nitrogen ions exited state mass density distribution and so on. We found that solar blind ultraviolet band energy is weak but not too weak in the UV band, so solar blind ultraviolet imaging is only relatively applicable to the conditions of daylight environment. Thus, we proposed ultraviolet multispectral imaging techniques and built an overall scheme of the ultraviolet multispectral imaging system, which contains the design of optical sub-system with filter wheel, the comparison and selection of UV enhanced back illuminated thinned CCD detector, the design of circuit with low noise and high intensive degree, the design of FPGA driving logic signals, the equipment of triple speed Ethernet with GigE data transmission means, and the design of PC received software based on WinpCap library of Ethernet data frames and the software used to subpackage big file and playback. We have completed the installation and light schooling of this system, and obtain a good image quality. We have obtained the system object inversion model by the methods of xenon lamp integrating sphere radiation calibration. After using different high voltage air discharge generators and taking images of the arc / corona targets, we have get the radiance of the targets and studied the relation between the system response, discharge voltage value, spatial gap distance and integrating time.The highlight of this dissertation could be summarized as followings:1) From the planning of system design, we have raised the imaging target from simple light-emitting target to air discharge low temperature plasma. We have analyzed the high voltage air discharge ultraviolet radiation properties from its process and principle, completed the ultraviolet spectral analysis of targets. Through the three classic and principle models of air discharge process(particle dynamics, hydrodynamics and mixing model), we have made finite element simulation analysis by numerical simulation software to get the corresponding results of the emission spectrum of air discharge process. Also, we have carried out rod-rod model for the same non-uniform electric field distribution that includes one-dimensional and two-dimensional structures.2) We have proposed and developed a principle prototype of ultraviolet multispectral imaging system for air discharge targets, contained with 240nm-280 nm,280nm-325 nm and 315nm-340 nm three channels. Ultraviolet multispectral imaging system can make full of air discharge ultraviolet emission spectra to take images with different bands, and be applicable for the imaging experimental research of specified ultraviolet targets. This system includes optical sub-system with filter wheel, low noise and high sensitivity of UV enhanced back illuminated thinned CCD detector, compact and efficient electronic circuit and FPGA driving signals technology, multi-thread PC software for the need of data transmission, image saving and display, and a big file playback and decompose software.3) We have taken images for atmospheric pressure high voltage air discharge targets(arc/corona) with ultraviolet multispectral imaging technology, echoing with the simulation results. By three different air discharge generator structures, we took images of arc, discussed the relations of high voltage, air gap and integrating time, and gotten the radiance of discharge plasma target by the inversion model via xenon lamp integral sphere calibration. Our work laid a solid foundation of ultraviolet technology and experiment basis for the further study and development of the air high voltage discharge.