Advances in Electromagnetic Flux-Compression Research

Recent findings from an ongoing research activity at Loughborough University into electromagnetic flux compression are: a) fast capacitor banks are more effective than slow banks; b) a differentially injected field can be more efficient than a cumulatively injected field; c) a new method of calculating forces has led to a much improved numerical predictions; d) a novel technique has been shown to be potentially able to generate record indoor fields and e) a cascade technique using aluminum powder can contribute to dramatically improve the compression efficiency, even in the presence of major liner instabilities. Due to the inherent space limitation, only the last of the five achievements will be presented in full detail here, although the oral presentation will briefly cover aspects from the other four. Electromagnetic flux compression requires high-quality liners, with copper being a much more effective material than the aluminum used in previous experiments at Loughborough for producing fields of 300 T. Unfortunately, similar small-size copper liners cannot be economically manufactured with sufficiently precise tolerances to prevent the development of liner instabilities during an implosion, leading to a much lower magnetic flux density than anticipated. This paper describes how the performance can however be dramatically improved by the use of an aluminum powder cascade, and presents results showing that the use of this technique has enabled flux densities up to 350 T to be generated using only a 70 kJ capacitor bank.