Some Comments on Short Pulse 10 Terawatt Diodes

Abstract

An area of considerable interest at the present time is generators capable of delivering 10 terawatts at voltages of one to a few megavolts. For some applications, the pulse can only usefully be 10 or 20 nanoseconds long. This implies the rise time of the pulse at the load must be short. Generators can be built for such requirements, using multichannel switching techniques and fast charging of the high speed section or sections. However, the diode presents significant difficulties and this note covers some aspects of the design of this and makes estimates of possible rise times. It should be emphazised that in a properly designed system the cathode interacts strongly with the diode design and this in turn interacts with the pulser design. Thus the design of the diode should not be considered in isolation. However, in this note this real life difficulty is partly sidestepped by taking a cathode of a given radius and assuming the inductance of the current flowing at or within this radius is small. With regard to the interaction of the diode/ cathode assembly back on the generator some comments on this will be made towards the end of the note.

SSWA/JCM/748/790