page_title: Explosively pumped flux compression generator
section_title: Elementary description of flux compression
hierarchical_section_title: Explosively pumped flux compression generator / How it works / Elementary description of flux compression
caption_attribution_description: Principles of magnetic flux compression - third phase Inspired by a drawing in a document from en:Los Alamos National Laboratory
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: An external magnetic field (blue lines) threads a closed ring made of a perfect conductor (with zero resistance).  The total magnetic flux  through the ring is equal to the magnetic field  multiplied by the area  of the surface spanning the ring.  The nine field lines represent the magnetic flux threading the ring.
  
  Suppose the ring is deformed, reducing its cross-sectional area.   The magnetic flux threading the ring, represented by five field lines, is reduced by the same ratio as the area of the ring. The variation of the magnetic flux induces a current (red arrows) in the ring by Faraday's law of induction, which in turn creates a new magnetic field circling the wire (green arrows) by Ampere's circuital law. The new magnetic field opposes the field outside the ring but adds to the field inside, so that the total flux in the interior of the ring is maintained: four green field lines added to the five blue lines give the original nine field lines.
  
  By adding together the external magnetic field and the induced field, it can be shown that the net result is that the magnetic field lines originally threading the hole stay inside the hole, thus flux is conserved, and a current has been created in the conductive ring.  The magnetic field lines are "pinched" closer together, so the (average) magnetic field intensity inside the ring increases by the ratio of the original area to the final area.
caption: Fig. 3: Magnetic field lines after compression.
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