Temperature dependent electron transport studies for diffuse discharge switching applications

A diffuse gas discharge switch must be capable of high speed, repetitive switching without significant degradation of its electron conduction and opening characteristics if it is to be useful in pulsed power switching applications. Whenever the switch is fired, the gas temperature T within the switch is expected to rise several degrees centigrade, and operating temperatures of several hundred degrees are likely for repetitively operated switches. The electron transport and rate coefficients, such as the electron drift velocity and the electron attachment coefficient for the most promising gas mixtures under study are expected to be funcions of T, and consequently, knowledge of these parameters as a function of T is desirable for modeling the operation of the diffuse discharge switch in practical application. Measurements of these parameters in C2F6/buffer gas (Ar, Ch4, N2) mixtures have been made and are reported. The electron attachment rate constant has also been measured for C2F6 and C3F8 as a function of the mean electron energy over the temperature range 300 less than or equal to T less than or equal to 750 K. For C2F6, the electron attachment rate constant has been found to increase by 30% over this temperature range, while for C3F6, the attachment rate constant first decreases when the temperature is increased to approximately 450 K and then significantly increases with increasing T. An interpretation of these measurements and their significance in repetitively operated diffuse discharge switching gas mixtures is outlined.