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High-power closing switches with graphite electrodes have been used in power-supply system for a large laser pump. The useful lifetime of this kind of switch is an interesting and important issue. Previous researchers have observed that the graphite erosion loss is proportional to the amount of transfer charge in a high-power pulsed discharge. Therefore, the erosion rate of graphite may be used for predicting and estimating the electrodes' useful lifetime. According to the mathematical model proposed in this paper, the lifetime of a closing switch with graphite electrodes is dependent upon several key parameters, including the dimensions of electrode, density, the erosion rate of graphite electrodes, undervoltage ratio, working temperature, and the amount of energy transfer. A mathematical formula describing the relationship between lifetime and those parameters has been deduced. Based on a newly developed spark-gap switch which can support over 100-C single transfer charge, this proposed lifetime model has been verified. This paper may quantitatively perform the function of guidance in engineering applications of graphite electrode switches in large pulsed-power facilities.
Date of Publication: Feb. 2011