Diagnostics of Streamer Discharges
Subnanosecond Spectral Diagnostics of Streamer Discharges
Tech Area / Field
- PHY-PLS/Plasma Physics/Physics
- PHY-NGD/Fluid Mechanics and Gas Dynamics/Physics
8 Project completed
Senior Project Manager
Russian Electrotechnical Institute named after V. I. Lenin / High-Voltage Research Center, Russia, Moscow reg., Istra-2
- NIIIT (Pulse Techniques), Russia, Moscow
- Muroran Institute of Technology, Japan, Muroran\nPrinceton University / School of Engineering and Applied Science / Department of Mechanical and Aerospace Engineering, USA, NJ, Princeton\nAnan College of Technology, Japan, Tokushima\nUMIST, UK, Manchester
Project summaryThe main project purpose is to research the fundamental properties of streamer discharges in airlike mixtures in short gaps. Today the streamer process (streamer stage, streamer discharge) is perceived as the fast initial stage of a full (or uncompleted) discharge in gases, accompanied by local ionization of a neutral component during streamer development. In the absence of the overvoltage on the discharge gap and/or if the external impedance is high enough, then some time after passing streamer waves, the streamer channel ionization relaxes and the initial gap conditions are restored.
Summary of the objectives of the project:
- to create the high-end research complex for spectrophotoelectrical diagnostics in multiphoton photomultiplier's (PM's) operational mode with a temporal resolution 0.2 ё 0.3 ns by means of modification of our today's experimental installation;
- to carry out the experimental investigations of streamer discharges in nanosecond-subnanosecond ranges by measuring the parameters of own emission and electric currents;
- to determine the important internal physical parameters in streamer head zone;
- to conduct the numerical and theoretical analysis of the obtained results.
The technical approach
Since 60-70th many researchers became widely to apply spectral-optical investigation methods with spatiotemporal resolution in order to determine fundamental physical parameters of streamer-leader discharges. At the same time the numerical and theoretical methods allowing microscopic processes and streamer dynamics with own internal physical parameters to be thoroughly modeled have been developed. Nowadays the detailed researches of streamer corona in a multiphoton (or one-photon) PM's operational mode can be realized at extremely high spatiotemporal resolution and photostrength, multiphoton PM's operational mode beng more informative.
The heart of our technical approach to research the streamer discharges in short air gaps is in:
- modeling the electrogasdynamic and kinetical processes in an airlike plasma, when the fast ionization wavefront is propagating;
- calculating the emission parameters in the first negative and second positive systems of molecular nitrogen;
- measuring and analyzing the light signals from the researched streamer waves both the spectral radiance etalon.
Temporal luminosity waveforms of these nitrogen bands are measured in a multiphoton PM's operational mode with highest spatiotemporal resolution. The absolute luminosity intensities of these bands are determined with the help of an additional emission source (tungsten incandescence strip), being as spectral radiance etalon.
By method of the relative and absolute luminosity intensities mentioned and also with the help of the various metrological characteristics of temporal luminosity waveforms, the techniques developed earlier and modified here allow the physical parameters in the streamer head zone to be determined. Those are electric field, electron number density, radius, front propagation velocity, concentration of excited states, field damping length etc.
The rate constant values of electron processes are calculated by solving Boltzmann's equation for electron energy distribution function in nitrogen-oxygen mixture. The calibrating procedure and algorithms have been developed on the base of nonlinear invariant transformation of pyrometrical signals from spectral radiance etalon.
The anticipated results:
- recovering a spatiotemporal structure of streamer waves at the dispersive limit (range) (*);
- the most self-consistent measurement and analysis of the above-mentioned physical parameters;
- obtaining information on the mutual internal dispersive characteristics of physical parameters;
- study of two-dimensional streamer structure and physical mechanisms of streamer propagation.
(*) Here the disperse limit (range) is perceived as the area supported metrologically and formed by the theoretic-descriptive, methodically-procedural and tool-hardware requirements and possibilities in the aggregate where reliable measurements can be realized with smallest joint disperse characteristics.
Potential role of foreign collaborators:
- analysis of the proposal by potential collaborator and working out recommendations for its adjustments and improvements in case the proposal is of interest to addressee;
- information exchange in course of project implementation and willingness to provide comments to the technical reports submitted by project participants to ISTC;
- assistance for the CIS Institute project participants in joining international conferences, seminars, workshops, by sending invitations, supporting their requests for visas, and (if possible) in covering part of expenses for trips condoned by ISTC;
- performing cross-checks of the results obtained in course of project implementation;
- conduction of joint seminars and workshops.