The Pseudospark

Abstract

The discovery of the pseudospark (Christiansen and Schul-theiss, 1979) fell into a period of stormy progress in pulsed power technology. The demands on the key element of pulse forming networks (PFN’s) - the switch - quickly exceeded the capabilities of commercial state-of-the-art switches like thyratrons and high-pressure spark gaps. At the same time, research and development efforts by the thyratron manufacturers had been reduced to a minimum. No new switch concepts promising to improve or combine the abilities of both thyratron and high-pressure spark gaps existed, especially for high repetition rate, long lifetime, short current risetime, as well as high peak current. The pseudo-spark, initially disregarded for switching purposes because of its modest dI/dt when used as a source of intense electron beams, soon found interest as a switch. It was realized that, in low-impedance PFN’s, the high impedance of the discharge rapidly drops to very low values, allowing risetimes of the current of several 10¹¹ A/s. The diffuse nature of the pseudospark also promised long lifetime, while the low operating pressure made short recovery times (and therefore high repetition rates) possible.