| The optical emission spectrum is an important plasma diagnostic techniques, and frequencetly used in the diagnostic of underwater pulse electrical discharges plasma, providing characteristic parameters of the discharge plasma. The emission spectrum of underwater pulse electrical discharges was measured by accumulating a number of dischange events and can not provide information on the temporal-spatial evolution of the single pulse discharges.Measuring temporal-spatial evolution dynamic characters is important for understanding the physical and chemical process of underwater pulse discharges.In this paper we constructed a high speed time-spatial resolvable spectrograph by combining an ultrahigh-speed frame camera system with a monochromator. This spectrograph can measure the emission spectrum of plasma and provide the spatial resolved optical emission spectrum. In this work, the spatial resolved emission spectrum for a single discharges pulse was measured by employing a point-to-plate electrode configuration. The main task and results are:(1) The spectrum conversion program was developed by using MATLAB for converting the spectrum images into spectrum curves.(2) The spectrograph performance was tested by using a 632.8 nm He-Ne laser beam. The instrument broadening is 0.15±0.01 nm while the grating resolution is 1200 g/mm and the width of entrance slit is 0.2 mm.(3) The spatial resolved emission spectrum of a single pulse discharges was measured by the high speed resolvable spectrograph. Electron density of a streamer filament was calculated, and it was found that the electron density is about 1017-1018/cm3.(4) The spatial resolved emission spectrum of a single pulse discharges was analyzed and the electron density spatial distribution was investigated. It was found that the distribution of electron density along the streamer filament is non-uniformity and the electron density at the vicinity of the tip of anode is larger than that at the streamer head. |
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