Voltage current characteristics of low current pulsed discharges in hydrogen and methane

Conference · Sun Dec 31 04:00:00 EST 1995

OSTI ID:212827

Stefanovic, I; Velikic, Z; Petrovic, Z Lj ^[1]

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1. Univ. of Belgrade, Zemun (Yugoslavia)

A recent survey of the available data on voltage current characteristics revealed a serious lack of data and discrepancies which are well beyond the acceptable. Recently a new series of measurements has been completed for the low current obstructed discharges both in diffuse (Townsend) and constricted regime. It has been shown that previous measurements were not affected by the local heating of the cathode as a possible cause of the large scatter of the data. Smooth V-I characteristics were obtained both in steady state measurements and in the pulsed measurements made in an attempt to minimize the perturbation of the cathode surface by ions. Negative differential resistance was obtained from V-I characteristics which explained the occurrence of self sustained oscillations below the onset of constriction. A model was developed which managed to explain all the observables in the experiment including the negative differential resistance (NDR), onsets of oscillation and the shape of oscillating voltage and current waveforms. The only adjustable parameter in the theory was the breakdown voltage fitted by adjusting the secondary electron yield to satisfy the experimental data. The experiments have been extended to study the transition to constrictions and to suggest a method of removing oscillations. The primary cause of the NDR is the specific dependence of the secondary electron yield on electric field and on current, the data for the yield as a function of effective electron energy were obtained from an independent experiment. Numerical solutions to the transport and space charge equations yielded theories which gave a more detailed description of the low current discharges and transition to the constricted glow. In the present paper we provide additional data for hydrogen and new data for methane in an attempt to provide good experimental results for quantitative comparisons with theories and numerical discharge models.

• OSTI ID: 212827
• Report Number(s): CONF-950749--
• Country of Publication: United States
• Language: English

Related Subjects

42 ENGINEERING
66 PHYSICS
ELECTRIC CURRENTS
ELECTRIC DISCHARGES
HYDROGEN
METHANE
PULSE TECHNIQUES
VOLTAGE DROP