Mechanism of pulsed surface flashover involving electron-stimulated desorption

Journal Article · Sat Mar 01 04:00:00 EST 1980 · J. Appl. Phys.; (United States)

DOI:https://doi.org/10.1063/1.327839· OSTI ID:5587379

Anderson, R A; Brainard, J P

A simple model is proposed to explain how a breakdown avalanche of secondary emission electrons can lead to surface flashover when an insulator in vacuum breaks down a few nanoseconds after high voltage is applied. The case of a plane insulator--vacuum interface perpendicular to parallel electrodes is considered. Positive surface charging is assumed to occur almost immediately upon application of the voltage, and the attendent secondary emission avalanche is assumed to be maintained at saturation throughout the prebreakdown time delay by field emission from the cathode electrode. Bombardment of the insulator by avalanche electrons desorbs a cloud of gas, which is partially ionized as it drifts through the swarm of electrons in the avalanche. The electric field at the cathode end of the insulator becomes enhanced as positive ions accumulate, which in turn increases the field emission and the rates of gas desorption and ionization. This and other regenerative processes rapidly lead to breakdown. Field enhancement at the cathode end of the insulator and increased field emission are individually considered in determining the prebreakdown time delay, with very similar results. The model predicts a time delay of the order of 10 ns at E=10 MV/m, which is in reasonable agreement with experimental observations. The proportionality we have observed between the time delay and the inverse square of the applied voltage is also predicted, as well as a dependence of the time delay on the insulator length. The model may also account for the improved performance of insulators coated with certain metal oxides.

• Research Organization: Sandia Laboratories, Albuquerque, New Mexico 87185
• DOE Contract Number: AC04-76DP00789
• OSTI ID: 5587379
• Journal Information: J. Appl. Phys.; (United States), Journal Name: J. Appl. Phys.; (United States) Vol. 51:3; ISSN JAPIA
• Country of Publication: United States
• Language: English

Related Subjects

640420* -- Fluid Physics-- Properties & Structure of Fluids-- (-1987)
75 CONDENSED MATTER PHYSICS
SUPERCONDUCTIVITY AND SUPERFLUIDITY
BREAKDOWN
CURRENTS
DESORPTION
ELECTRIC CURRENTS
ELECTRIC DISCHARGES
ELECTRICAL EQUIPMENT
ELECTRICAL INSULATORS
ELECTRODES
ELECTRONS
ELEMENTARY PARTICLES
EMISSION
EQUIPMENT
FERMIONS
FLASHOVER
INTERFACES
LEPTONS
MATHEMATICAL MODELS
PULSES
SECONDARY EMISSION
SURFACES