Spectroscopic investigation of impulse corona discharges

The spectra of corona discharges in air at atmospheric pressure, in a 06 m point-plane gap under positive impulse voltage, have been measured in the near-ultraviolet and visible regions. Two types of corona discharges have been investigated: the first corona which develops from the electrode tip; and the leader coronas which develop successively from the leader tip. The spectrum of the first corona appears to be due almost exclusively to molecular nitrogen (second positive system), while that of the leader coronas also contains some weaker radiation of molecular positive ions of nitrogen (first negative system) and oxygen (first and second negative system), together with some of the brighter lines of atomic oxygen. The radiation of molecular oxygen and atomic nitrogen does not appear with a measurable intensity. A comparison of the relative intensities of the N2 second positive and N2+ first negative bands with low-pressure data indicates that under high-pressure conditions the repartition of population in the various vibrational levels is affected by secondary deactivation processes (electronic and vibrational quenching). By taking into account such processes, the relative intensities of a number of these bands have been theoretically calculated for different electron energy distributions. A comparison between the present experimental and theoretical results shows that a Druyvesteyn energy distribution is more likely for the electrons in the avalanches developing in front of the streamer tip. Furthermore, this comparison makes possible the evaluation of the electron mean energy and the average field in these avalanches: they both turn out to be larger in the leader coronas than in the first corona. This difference in the electron mean energy is responsible for the different spectral characteristics of the first and leader coronas.

[1]  V. A. B. M. D.Phil..  XCI. On the attachment of electros to gas molecules , 1925 .

[2]  R. Crompton,et al.  Experimental studies of the motions of slow electrons in air with application to the ionosphere , 1953, Proceedings of the Royal Society of London. Series A. Mathematical and Physical Sciences.

[3]  L. Kline,et al.  Computer Simulation of Electrical Breakdown in Gases; Avalanche and Streamer Formation , 1972 .

[4]  R. C. Axtmann,et al.  Vibrational Relaxation and Electronic Quenching of the C 3Πu (υ′ = 1) State of Nitrogen , 1971 .

[5]  J. Kritzinger.  Impulse Corona and the Pre-Breakdown Mechanism of Long Sparks , 1963, Nature.

[6]  B. Brocklehurst,et al.  Mechanisms of Excitation of Luminescence in Nitrogen Gas by Fast Electrons , 1967 .

[7]  E. Bauer,et al.  Calculation of Inelastic Electron—Molecule Collision Cross Sections by Classical Methods , 1965 .

[8]  F. A. Sharpton,et al.  Apparent Cross Sections of N 2 for Electron Excitation of the Second Positive System , 1967 .

[9]  F. R. Simpson,et al.  Absolute cross sections for electron excitation of the second positive bands of nitrogen , 1969 .

[10]  B. Brocklehurst.  Luminescence of gases excited by high-energy radiation. Part 1.—Collisional deactivation in nitrogen , 1964 .

[11]  K. B. Mitchell.  Fluorescence Efficiencies and Collisional Deactivation Rates for N2 and N2+ Bands Excited by Soft X Rays , 1970 .

[12]  A. Zaazou,et al.  Experimental and theoretical studies of the behaviour of slow electrons in air. I , 1949, Proceedings of the Royal Society of London. Series A. Mathematical and Physical Sciences.

[13]  M. R. Amin.  Fast Time Analysis of Intermittent Point-to-Plane Corona in Air I. The Positive Point Burst Pulse Corona , 1954 .

[14]  Streamer Mechanism and Main Stroke in the Filamentary Spark Breakdown in Air as Revealed by Photomultipliers and Fast Oscilloscopic Techniques , 1961 .

[15]  K. Wagner.  Die Entwicklung der Elektronenlawine in den Plasmakanal, untersucht mit Bildverstärker und Wischverschluß , 1966 .

[16]  D. T. Stewart.  Electron Excitation Functions of the First Negative Bands of N2 , 1956 .

[17]  A. G. Gaydon,et al.  The identification of molecular spectra , 1950 .

[18]  M. R. Amin.  Fast Time Analysis of Intermittent Point‐to‐Plane Corona in Air. II. The Positive Pre‐Onset Streamer Corona , 1954 .

[19]  R. John,et al.  Electron Excitation of the First Positive Bands of N 2 and of the First Negative and Meinel Bands of N 2 , 1969 .

[20]  E. Poss,et al.  ABSOLUTE FLUORESCENCE YIELDS OF 3914-A PHOTONS FROM N$sub 2$ AND AIR EXCITED BY RELATIVISTIC ELECTRONS. , 1970 .

[21]  R. C. Klewe,et al.  A model of impulse breakdown in divergent field geometries , 1972 .

[22]  I. Gallimberti.  A computer model for streamer propagation , 1972 .

[23]  C. T. Phelps.  Field‐enhanced propagation of corona streamers , 1971 .

[24]  M. Feast.  On the Schumann-Runge O2 Bands emitted at Atmospheric Pressure , 1949 .