An explosive-driven ferromagnetic generator (EDFMG, explosively pumped ferromagnetic generator, EPFMG, or FMG) is a compact

pulsed power Pulsed power is the science and technology of accumulating energy over a relatively long period of time and releasing it instantly, thus increasing the instantaneous power. They can be used in some applications such as food processing, water treatme ...

generator, a device used for generation of short high-

voltage Voltage, also known as electric pressure, electric tension, or (electric) potential difference, is the difference in electric potential between two points. In a static electric field, it corresponds to the work needed per unit of charge to m ...

high-

current Currents, Current or The Current may refer to: Science and technology * Current (fluid), the flow of a liquid or a gas ** Air current, a flow of air ** Ocean current, a current in the ocean *** Rip current, a kind of water current ** Current (stre ...

pulse by releasing energy stored in a

permanent magnet A magnet is a material or object that produces a magnetic field. This magnetic field is invisible but is responsible for the most notable property of a magnet: a force that pulls on other ferromagnetic materials, such as iron, steel, nickel, ...

. It is suited for delivering high-

pulses (kiloamperes) to low- impedance loads. The FMGs consist of a permanent magnet (usually a

neodymium magnet A hard_disk_drive.html"_;"title="Nickel-plated_neodymium_magnet_on_a_bracket_from_a_hard_disk_drive">Nickel-plated_neodymium_magnet_on_a_bracket_from_a_hard_disk_drive_ file:Nd-magnet.jpg.html" ;"title="hard_disk_drive_.html" ;"title="hard_disk_d ...

), a

high explosive An explosive (or explosive material) is a reactive substance that contains a great amount of potential energy that can produce an explosion if released suddenly, usually accompanied by the production of light, heat, sound, and pressure. An exp ...

charge, and a pickup coil. They are a kind of

phase transition In chemistry, thermodynamics, and other related fields, a phase transition (or phase change) is the physical process of transition between one state of a medium and another. Commonly the term is used to refer to changes among the basic states of ...

generators, utilizing pressure-induced magnetic phase transition effect. By adjusting the number of turns of the coil, which can be as low as a single turn, the generator can be designed for delivery of high-current low-voltage pulses or, with more turns, low-current high-voltage pulses. The

shock wave In physics, a shock wave (also spelled shockwave), or shock, is a type of propagating disturbance that moves faster than the local speed of sound in the medium. Like an ordinary wave, a shock wave carries energy and can propagate through a med ...

generated by explosion destroys the

magnetic domain A magnetic domain is a region within a magnetic material in which the magnetization is in a uniform direction. This means that the individual magnetic moments of the atoms are aligned with one another and they point in the same direction. When c ...

s in the magnet, cause loss of the

magnetic field A magnetic field is a vector field that describes the magnetic influence on moving electric charges, electric currents, and magnetic materials. A moving charge in a magnetic field experiences a force perpendicular to its own velocity and to ...

, and the very sudden change induces a high-peak

electric current An electric current is a stream of charged particles, such as electrons or ions, moving through an electrical conductor or space. It is measured as the net rate of flow of electric charge through a surface or into a control volume. The moving pa ...

in the surrounding coil. Both the shock wave directions parallel to the vector of magnetization (longitudinal) and perpendicular (transverse) are possible to be used. One of the possible configurations is a ring magnet with the explosive charge in its center. EDFMGs are especially well suited as seed power sources for

explosively pumped flux compression generator An explosively pumped flux compression generator (EPFCG) 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 d ...

s and can be used for charging capacitor banks. A generator coupling an EDFMG containing an 8.75 cm³ of magnetic material with a spiral

vector inversion generator A vector inversion generator (VIG) is an electric pulse compression and voltage multiplication device, allowing shaping a slower, lower voltage pulse to a narrower, higher-voltage one. VIGs are used in military technology, e.g. some directed-energ ...

yielded a pulse of amplitude over 40 kilovolts with a

rise time In electronics, when describing a voltage or current step function, rise time is the time taken by a signal to change from a specified low value to a specified high value. These values may be expressed as ratiosSee for example , and . or, equivalen ...

of 6.2 nanoseconds. Generators delivering pulses over 50 kV and 5 kA were demonstrated.E.F. Talantsev ''et al.'
"Analytical Model for Explosive-Driven Ultracompact Shock-Wave Ferromagnetic Generators"
Vol. 115 (2009) Acta Physica Polonica A No. 6, Proceedings of the 2nd Euro-Asian Pulsed Power Conference, Vilnius, Lithuania,September 22–26, 2008 Ultra-compact generators with diameter less than 50 mm were developed.

References

{{reflist, 30em
Explosive pulsed power: an enabling technology

Analytical model for explosive-driven ultracompact shock-wave ferromagnetic generators
Pulsed power Ferromagnetism

See also

References