Explosively formed fuse opening switches for multi-megajoule applications

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 /spl mu/s. 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 /spl sim/3 TW for 2 /spl mu/s has become routine, and we describe its characteristics and give data from a number of tests.