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Home > About us > Media > Archived news > 2021 > Chenyang Ding defended his PhD thesis on "Experimental study of plasma parameters in nanosecond surface dielectric barrier filamentary discharge".
Chenyang Ding defended his PhD thesis on "Experimental study of plasma parameters in nanosecond surface dielectric barrier filamentary discharge".
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On May 26, 2021, Chenyang Ding defended his PhD thesis on "Experimental study of plasma parameters in nanosecond surface dielectric barrier filamentary discharge". Svetlana Starikovskaia was the supervisor of Chenyang’s PhD thesis.
Due to the crisis, the PhD defence was online.
Abstract:
The thesis presents the study of streamer-to-filament transition in a single shot high pressure surface nanosecond barrier discharge in non-reactive gases (nitrogen, oxygen and their mixtures). It was shown that at negative polarity, addition of oxygendoes not influence the transition significantly while at positive polarity, 1% of oxygen increases the threshold voltage by 10 kV; Emission spectra of the discharge with high temporal (1 ns) and spatial (500 μm) resolution were taken around the transition point. A sharp increase from typical streamer ne (1015 cm-3) to a high ne(1019cm-3) within 1 ns was obtained experimentally. It was shown that electron temperature stays high, 1.7 eV, after the discharge.
Dynamics of morphology of plasma was studied with the help of ICCD micro imaging. For both polarities, before transition to filament, a streamer channel decreases in diameter and accelerates; backward emission starts from the obtained protrusion to the electrode. Continuum wavelength (cw) emission, typical for the filament, appears when the backward emission comes to the high voltage electrode; High specific deposited energy (6-7 eV/particle) was found experimentally in the filament; It was shown theoretically that the transition can be as fast as observed only under conditions when electronically excited N2 molecules participate in dissociation and ionization by electron impact. In this case, complete dissociation is observed; Gas temperature is equal to electron temperature and electron density decay is defined by a gas cooling.
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