Explosively formed fuse opening switches for multi-megajoule applications

Abstract

High explosive pulsed power (HEPP) systems are capable of
generating very high energies in magnetic fields. Such stored energy is
usually developed on time scales of a few tens or hundreds of
microseconds. Many applications require shorter pulses and opening
switches provide one way to use the large energy available for faster
applications. With current flowing in an inductive circuit, introducing
resistance produces voltage that can be used to drive current into a
load. For an opening switch with a fast rising resistance, the load
current rise time is determined by the R/L time constant of the circuit.
A significant fraction of the circuit energy must be dissipated in the
process, and in applications where very large energies must be dealt
with only a few types of switches can be used. Experiments with high
explosive driven opening switches have produced a few switches that can
carry tens of MA current, and open on the time scale of one or a few
μs. We have specialized in a type of switch that we call an
explosively formed fuse (EFF), and the use of this switch in the is MJ
Procyon system is the subject of this paper. Operation of the EFF switch
at levels of ~3 TW for 2 μs has become routine, and we describe its
characteristics and give data from a number of tests