Journal
PLASMA SOURCES SCIENCE & TECHNOLOGY
Volume 31, Issue 4, Pages -Publisher
IOP Publishing Ltd
DOI: 10.1088/1361-6595/ac5c5f
Keywords
streamer-to-filament transition; nanosecond surface dielectric barrier discharge; micro-scale; bi-directional ionization wave
Categories
Funding
- French-Russian international research project IRP 'Kinetics and physics of pulsed plasmas and their afterglow' (CNRS)
- French National Research Agency (ASPEN Project)
- French General Directorate of Armaments (DGA) under the EP-DGA convention 2790 'Interaction of detonation with low temperature plasma'
- China Scholarship Council (CSC)
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The fine structure of a streamer-to-filament transition in a high-voltage nanosecond surface dielectric barrier discharge in molecular nitrogen at pressure P = 6 bar was investigated using ICCD microimaging. An intermediate discharge structure, existing for only a few nanoseconds, was observed between two discharge modes: streamer discharge and filamentary discharge. The structure consists of thin channels propagating faster than the main ionization front and transforms into a bi-directional ionization wave. The study provides important insights into the nature of the streamer-to-filament transition.
The fine structure of a streamer-to-filament transition in a single-shot high-voltage nanosecond surface dielectric barrier discharge in molecular nitrogen at pressure P = 6 bar was studied with the help of ICCD microimaging. An intermediate discharge structure, existing for only a few nanoseconds, was observed in the time interval between two discharge modes: streamer discharge, with a typical electron density of n (e) similar to 10(15) cm(-3), and filamentary discharge, with n (e) similar to 10(19) cm(-3). The structure was observed for both polarities of the high-voltage electrode. The structure can be briefly described as a stochastic appearance of thin channels propagating a bit faster than the main ionization front of merged surface streamers, transforming in a few nanoseconds in a bi-directional ionization wave. One wave, which we associate with a feather-like structure in optical emission, propagates further away from the high-voltage electrode, and another, a backward wave of emission, propagates back towards the edge of the high-voltage electrode. When the backward wave of emission almost reaches the high-voltage electrode, the filament appears. Plasma properties of the observed structure were studied to better understand the nature of a streamer-to-filament transition. Theoretical analysis suggests that the instability of a flat front of ionization wave (Laplacian instability) triggers the streamer-to-filament transition, and that a surface stem (a tiny region with enhanced electron density) should be in the origin of the bi-directional ionization wave.
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