Dielectric Waveguide Excitation By Microwave Plasma And Microsecond Pulse Plasma Experimental Research

With increasing the plasma knowledge of human beings, the technology of plasma has been applied on three big fields of sources, matter and material, and environment and universe. In particular, conventional thruster system cannot accomplish exploring planets, deep space and interstellar sail missions and so on. Developing the electric propulsion system may be a feasible method. In addition, it has also been applied on biosensor and cancer treats and so on. In my dissertation, my work had been performed in physics experiments from practical applications of the electric propulsion and microwave discharge, i.e., investigation of relative physics experiments in the plasma excited by microwave which is guided by cylindrical dielectric waveguide and the microsecond plasma produced by pulsed plasma thruster (PPT). The main contents in the paper are as follow:1) Under helps of my adviser Professor Liang and Doctor Liu Feng, the setups of microwave discharge and PPT had been accomplished. The suitable cylindrical Teflon rod and its fitting were designed, and probe system served for the plasma diagnostic was designed. The power units were adjusted with especially adjusting ignition system and selecting the suitable spark plug.2) The mode excited by cylinder dielectric waveguide was analyzed and the mechanism of the variation of plasma source with different power supply was explained. Dense plasma(10¹²cm^-3) was got near the surface of the dielectric rod. Results from Langmuir probe showed radial electron density and temperature decreased linearly and exponentially respectively along the radial direction, while these two parameters increased with the input power supply of microwave. Axial electron temperature and density descended along the axial direction. As the pressure ascended from 20Pa to 40Pa, radial electron density increased while the temperature decreased.3) Standing wave phenomenon was explained in aid of electromagnetic theory. When microwave conveyed to the end of dielectric rod, the incident wave and reflected wave formed standing wave in the rod. With the increase of input power of microwave, the brightness and number of nodes experienced dramatic changes.4) Electron density in the channel of pulsed plasma thruster by using the Stark broadening for the first time. Stark FWHM was obtained by separating the Lorentzian profile from the Gaussian profile using convolution and deconvolution programs and computing the order of electron density is 10²² m^-3. With increasing the main capacitor discharge energy, electron density increases very minimally. And it is in excellent agreement with other experimental and theoretical data. Electron temperature was obtained by Boltzmann plot method in the PPT, never changing with increasing the main capacitor discharge energy. There are qualitative conclusions that electron temperature decreases with increasing the gap of the electrodes and increases with increasing the width of the electrodes.