An empirical formula for gas switch breakdown delay

An empirical scaling relationship between the mean electric field and the breakdown time has been found. Many divergent sets of data were used from breakdown experiments on power lines, laser-triggered switches, trigatrons, e-beam triggered gaps, sharp point electrode to plane gaps, and uniform field gaps. This relationship builds on the Felsenthal and Proud data/sup 1/ and extends their breakdown time delay (formative time) data by three orders of magnitude and into the region of interest for triggered gas switching. The empirical relationship shows that the data bases are related by /spl rho//spl tau/ = 97800 (E//spl rho/)/sup -3.44/ where /spl rho/ is the gas density in gm/cc, /spl tau/ is the time delay to breakdown in seconds, and E is the average electric field in kV/cm. The data indicates that electrically triggered gaps, laser triggered gaps, and untriggered gaps are governed by the same time-delay processes. Predictions can be made of trigger gap geometry, trigger delays, and trigger polarity effects. Breakdown delays of sub-centimeter-long to at least 8-meter-long gaps in air with either high or low field-enhanced electrodes are described by this equation. In addition, this relationship appears to be valid for a variety of gases and even accurately predicts the breakdown delay of mixtures of air and SF/sub 6/.