page_title: Explosively pumped flux compression generator
section_title: How it works
hierarchical_section_title: Explosively pumped flux compression generator / How it works
caption_attribution_description: Magnetic flux through a surface
context_page_description: An explosively pumped flux compression generator is a device used to generate a high-power electromagnetic pulse by compressing magnetic flux using high explosive.
  An EPFCG only ever generates a single pulse as the device is physically destroyed during operation. An EPFCG package that could be easily carried by a person can produce pulses in the millions of amperes and tens of terawatts. They require a starting current pulse to operate, usually supplied by capacitors.
  Explosively pumped flux compression generators are used to create ultrahigh magnetic fields in physics and materials science research and extremely intense pulses of electric current for pulsed power applications. They are being investigated as power sources for electronic warfare devices known as transient electromagnetic devices that generate an electromagnetic pulse without the costs, side effects, or enormous range of a nuclear electromagnetic pulse device.
  The first work on these generators was conducted by the VNIIEF center for nuclear research in Sarov in Soviet Union at the beginning of the 1950s followed by Los Alamos National Laboratory in the United States.
context_section_description: Magneto-explosive generators use a technique called "magnetic flux compression", described in detail below. The technique is made possible when the time scales over which the device operates are sufficiently brief that resistive current loss is negligible, and the magnetic flux through any surface surrounded by a conductor (copper wire, for example) remains constant, even though the size and shape of the surface may change.
  This flux conservation can be demonstrated from Maxwell's equations. The most intuitive explanation of this conservation of enclosed flux follows from Lenz's law, which says that any change in the flux through an electric circuit will cause a current in the circuit which will oppose the change. For this reason, reducing the area of the surface enclosed by a closed loop conductor with a magnetic field passing through it, which would reduce the magnetic flux, results in the induction of current in the electrical conductor, which tends to keep the enclosed flux at its original value. In magneto-explosive generators, the reduction in area is accomplished by detonating explosives packed around a conductive tube or disk, so the resulting implosion compresses the tube or disk. Since flux is equal to the magnitude of the magnetic field multiplied by the area of the surface, as the surface area shrinks the magnetic field strength inside the conductor increases.  The compression process partially transforms the chemical energy of the explosives into the energy of an intense magnetic field surrounded by a correspondingly large electric current.
  The purpose of the flux generator can be either the generation of an extremely strong magnetic field pulse, or an extremely strong electric current pulse; in the latter case the closed conductor is attached to an external electric circuit.   This technique has been used to create the most intense manmade magnetic fields on Earth; fields up to about 1000 teslas (about 1000 times the strength of a typical permanent magnet) can be created for a few microseconds.
caption: For a constant intensity magnetic field of magnitude B traversing a surface S, the flux Φ is equal to B times S.
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