Abstract
The streamer breakdown criterion for computing the uniform field breakdown voltages is examined for gaps filled with Air, N2 and SF6. The critical avalanche size is obtained for these gases for different values of the parameter pd and it is shown that this size depends upon the type of the gas, its pressure, and the gap length. Furthermore, the amount of error introduced in the breakdown voltage calculations is computed by assuming a critical avalanche size of 108 electrons as a condition for the streamer formation. he results are discussed briefly.