Investigations of overvoltage breakdown

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Title: Investigations of overvoltage breakdown
Author: Levinson, Scott Joseph
Abstract: An experiment has been constructed to investigate the highly overvolted , electrical gas discharge for the following parameters : pressure ( < 1 Torr - 1350 Torr ) , electrode spacing (1 and 2 cm ) , electric field (55 -110 kV /cm ) and electrode material (aluminum , brass , and graphite ) . In order to determine the effects of these parameters on the statistics associated with the observational time lag , an automated data acquisition system has been built to reduce large amounts of time lag data . An insulator has been placed over the anode in a number of experiments to examine the current waveforms resulting from electron space charge motion in the gap during the pre -breakdown stage . The results indicate that large^ fast rising ( ~ 1 ns ) currents ( ~ 100 A ) exist in the gap before a conducting plasma channel bridging the cathode and anode is formed . These initial currents appear to be the result of runaway electron space charge motion . The results of the statistical investigation indicate that : (1 ) the graphite electrode is a promising candidate in low jitter switching applications because of its large emissivity ( ~ le ~ /ns ) ; (2 ) the statistics associated with the formative time lag are comparable to those of the statistical time lag (when graphite electrodes are used ) at overvoltages as high as 400 % . An apparent pressure dependency of the electron emission rate is a consequence of this result ; (3 ) the formative time lag reaches an asymptotic value at the highest values of overvoltage investigated ( - 2800 % ) ; and (4 ) the formative time lag is significantly larger than that predicted by the Streamer Theory (Raether's criteria ) , particularly at the highest values of overvoltage .
URI: http : / /hdl .handle .net /2346 /16221
Date: 1981-08


Investigations of overvoltage breakdown. Master's thesis, Texas Tech University. Available electronically from http : / /hdl .handle .net /2346 /16221 .

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