Design optimization of End Cover of an explosive driven helical flux compression generator through explicit numerical simulations

Explosive Driven Helical Flux Compression Generator (FCG) is a single shot device used to produce very high current. It finds applications in various advanced technologies like plasma research, EMP weapons, high magnetic field generators etc. Single end initiated helical FCG is most widely used among their several forms. In this paper, design of End Cover, a crucial component of a single end initiated FCG through numerical simulation code AUTODYN
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is investigated. In a single end initiated FCG, explosive filled armature is initiated from one end which causes the armature to expand in a conical manner to the other end. The expanding armature results in inductance collapse and hence current amplification. The End Cover forms one terminal for realising current output, is electrically connected with armature and thus should remain in through contact with it throughout the FCG action. Mechanical design of End Cover is crucial as expanding armature interacts with it during FCG action. If the End Cover is not properly designed, a break in the continuity can occur causing the loss of energy. This loss of energy leads to drastic reduction in the output of this device. Interaction of the FCG End Cover with the expanding aluminium armature under explosive action is studied in detail for various geometries. Through these simulations better insight of the problem is evolved which is otherwise very difficult to capture even with sophisticated experimental techniques. An optimum design of the End Cover for a single end initiated FCG is suggested.