Interruption of the explosion of plasma initiator wires

Many designs of plasma generators, used for the electrothermal-chemical (ETC) gun concept, utilise a length of fuse wire to initiate an electrothermal plasma discharge. The detailed study of the generation of the plasma from such devices has been carried out at QinetiQ for a number of years. Such studies have allowed the development and validation of the computer hydrocode EDEN-IB, where the formation of the plasma is central to predicting the mass and energy flux from the plasma generator. Such studies have also been of interest and relevance to the fuse-wire, electric armour and lightning communities. This paper is concerned with the fragmentation of the wire during the early stages of plasma development. Wire fragmentation has been researched for many years and has been shown to occur with the wire still in the solid phase under some experimental conditions. However, it is a matter of debate whether solid phase fragmentation of the plasma initiation wire is occurring with discharge current densities and rise-times typical for ETC gun research. Recent experimentation, using a fast-switching thyristor to divert the current from the exploding wire, has allowed the fragmentation process to be studied. Results of this work are reported in this paper.