Novel high-resolved spectroscopic studies of positive streamer corona

摘要

We have developed a fully self-consistent method of diagnostics of streamer discharge plasmas based on analysis of absolute intensities of the second positive (SPS) and first negative (FNS) systems of molecular nitrogen. The theory of the method combines a spectroscopic technique for calculation of temporal waveforms of the nitrogen absolute SPS and FNS (0,0)-band emission and a self-consistent semi-analytical parametric axially symmetric 1.5D model of the filamentary streamer head. The spectroscopic technique takes into account characterizations of all units of the measuring spectro-optical channel, including spatiotemporal resolution and resolution in wavelength. The model of the streamer head is characterized by some trial consistent allowable parametric on-axis profile of the electric field combined with the electron and total space charge number density profiles fully self-consistent each with other and with the trial electric field; all those expanded to 2D configuration via ellipse-like geodesic lines. The absolute values and the synchronous ratio of the 1L spatially and time-resolved cross-correlated temporal waveforms of the SPS to FNS (0,0)-bands have been used to reconstruct 2D structure of the streamer head. With a procedure fitting the directly computed output voltage waveforms to the experimental ones, the peak values of the electric field and of the electron number density within streamer head at mid-gap distances have been found to be 430-500 Td and (2-K3)xlO14 cm"3, respectively. The corresponding absolute electric field became thus 70-5-80 kV/cm at initial gas temperature within the repetitive streamer region of 450 K. The results corroborate principal conclusions of the current-day streamer theory and numerical modeling.