Incomplete Breakdown: a Cathode De-ionization Effect

Abstract

CONSIDERABLE interest has been taken in the phenomenon of 'stepped' breakdown in the electric spark, and experimental investigations have been made, notably by Tamm¹ and others², using oscillographic records of the collapse of voltage across the gap. Studies have also been made by Raether³ of the growth of the space charges in the gap, using the cloud-chamber method. These experiments were mainly concerned with short gaps of the parallel-plate type in air at reduced densities. In many practical applications of short spark gaps, however, high gas densities are required, and if similar effects are found to occur at these high gas densities, any 'stepping' of the voltage across the gap during the initial phase of the breakdown can have serious consequences in that complete breakdown of the gas insulation is prevented. The gap can thus develop an appreciable resistance in which considerable power may be dissipated. The occurrence of this effect would render the spark gap useless in those circuits which require sudden surges of high peak-current through a low-resistance path.