Design of a command-triggered plasma opening switch for terawatt applications

Abstract

The crucial element of an inductive energy storage system is the opening switch. In microsecond and nanosecond pulsed power systems the plasma opening switch has been in use for many years. The development of the triggered switch addresses three important areas: complete de-coupling of the closed phase and the opening phase will allow improved performance, especially at longer conduction times; the simplified physics allows for easier modeling because of a better-defined geometry; and triggering will reduce jitter of the output pulse. Improving performance will allow longer conduction time, and triggering will negate the naturally increased self-operating jitter at longer conduction time. The triggered switch system is based on moving the plasma switch armature with a magnetic field. Up until the time the armature is pushed away, it is held in place against the drive current magnetic pressure by a second magnetic field. Our system is designed to deliver 1-2 terawatts of usable load power at multi-megavolt potentials. We define usable load power as the product of load voltage and load cathode current. The length of the vacuum storage inductor defines the 35 ns pulse length. This paper shows the design of the switch and trigger system, which is conservatively designed to provide a wide range of trigger signals. The trigger power for this system is important for cost reasons. The first experiments will use a trigger level of ten percent of the output pulse; we describe design features intended to reduce the amount of trigger power needed. Particle-in-cell simulations of the active trigger are also shown.