Transient Glow Research Articles

The Observation and the Simulation of a Transient Glow Discharge in a Trigatron Gap

The characteristics of the transient glow discharge were studied experimentally and also by a simulation in a trigatron gap. The ionization front which is formed at the beginning of a trigger discharge, propagates to the anode in a main gap and after then, the glow discharge is formed. These phenomena are verified and these mechanisms are clarified in detail by the simulation. This discharge changes into an arc discharge after the subsequent discharge similar to a channel discharge observed in a parallel-plate gap. The jitter of the switching time is made clear to be caused by the fluctuation in a duration time of the glow discharge. This mechanism is discussed in detail.

Oscillatory characteristics of a low-pressure DC discharge in air

Oscillations in a transient DC glow discharge at different pressures in air have been studied, and the effect of pressure, voltage and current on frequency, amplitude and cut-off current is shown. A mechanism for the generation of oscillation based on space-charge field modification is discussed.

Observations of the arc-forming stages of spark breakdown using an image intensifier and converter

The development of high-current transient glow and arc discharges over a wide overvoltage range in a 3 cm uniform-field gap has been investigated in nitrogen, oxygen and mixtures of these gases at sub-atmospheric pressures, using an `Imacon' image converter and an EMI 4-stage image intensifier. Streak photographs have been obtained which show clearly the propagation of luminous fronts in both anode and cathode directions during the development of ionization from the prebreakdown stage of the discharge to the final arc.

The transient glow discharge in nitrogen and dry air

The duration of the transient glow discharge preceding the arc stage of uniform-field gas breakdown has been measured for nitrogen and air. These measurements have been made for gaps up to 3 cm at gas pressures of 300 and 500 Torr, in the overvoltage range 4%less-than-or-eq, slantΔVless-than-or-eq, slant20%. It has been shown that the glow duration is strongly dependent upon the equivalent series circuit resistance, and this explains the poor agreement between the results of previous investigations.During spark conditioning, a form of breakdown consisting of a very diffuse glow, with no subsequent arc discharge, has been observed. Some of the factors affecting the occurrence of this interesting phenomenon have been studied.

Investigation of the glow phase in spark discharges

The axial voltage distribution of spark discharges in hydrogen, nitrogen and carbon dioxide is studied during the transient glow phase over a wide range of pressures. The results indicate that a glow mode develops in discharges which is initiated by the Townsend mechanism and is independent of external impedance. It is characterized by fixed values of cathode fall voltage and the ratio electric field to pressure in the positive column.

The Development of Spark Discharges in Hydrogen

Streak photography has been used to supplement the earlier shutter photo. graphic investigation of Doran and Meyer (1967) using the same coaxial cable discharge circuit. Additional information has also been obtained from measurement of the potential distribution between the electrodes at two stages in the spark development. Redistribution of space charge is shown to give rise firstly to a transient diffuse glow discharge that has a close similarity with a normal d.c. glow discharge. It has also been shown that, even while the diffuse glow discharge expands, a partial constriction occurs in which most of the current flows along a narrow axial column. The resulting maximum in electron density eventually causes a rapid increase in dissociation of molecular hydrogen on the axis of the discharge brought about by a rise in the gas temperature. Owing to its greater electrical conductivity this axial column soon carries the entire current and the discharge becomes filamentary though still being maintained by a high cathode fall field, which exists until a sudden change in the cathode mechanism gives rise to the low voltage arc channel. Both the filamentary glow and arc columns are observed to expand according to an r cc ti law.

Cathode spots in the transient glow discharge in nitrogen

Cathode spots, arranged in a regular pattern of concentric circles, have been observed to occur during the transient glow discharge stage of the impulse breakdown of uniform field gaps in nitrogen.