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Flux pumping is a method for magnetising superconductors to fields in excess of 15 teslas. The method can be applied to any type II superconductor and exploits a fundamental property of superconductors. That is their ability to support and maintain currents on the length scale of the superconductor. Conventional magnetic materials are magnetised on a molecular scale which means that superconductors can maintain a flux density orders of magnitude bigger than conventional materials. Flux pumping is especially significant when one bears in mind that all other methods of magnetising superconductors require application of a magnetic flux density at least as high as the final required field. This is not true of flux pumping. An electric current flowing in a loop of superconducting wire can persist indefinitely with no power source. In a normal conductor, an electric current may be visualized as a fluid of electrons moving across a heavy ionic lattice. The electrons are constantly colliding with the ions in the lattice, and during each collision some of the energy carried by the current is absorbed by the lattice and converted into heat, which is essentially the vibrational kinetic energy of the lattice ions. As a result, the energy carried by the current is constantly being dissipated. This is the phenomenon of electrical resistance. The situation is different in a superconductor. In a conventional superconductor, the electronic fluid cannot be resolved into individual electrons. Instead, it consists of bound ''pairs'' of electrons known as Cooper pairs. This pairing is caused by an attractive force between electrons from the exchange of phonons. Due to quantum mechanics, the energy spectrum of this Cooper pair fluid possesses an ''energy gap'', meaning there is a minimum amount of energy Δ''E'' that must be supplied in order to excite the fluid. Therefore, if Δ''E'' is larger than the thermal energy of the lattice, given by ''kT'', where ''k'' is Boltzmann's constant and ''T'' is the temperature, the fluid will not be scattered by the lattice. The Cooper pair fluid is thus a superfluid, meaning it can flow without energy dissipation. In a class of superconductors known as type II superconductors, including all known high-temperature superconductors, an extremely small amount of resistivity appears at temperatures not too far below the nominal superconducting transition when an electric current is applied in conjunction with a strong magnetic field, which may be caused by the electric current. This is due to the motion of vortices in the electronic superfluid, which dissipates some of the energy carried by the current. If the current is sufficiently small, the vortices are stationary, and the resistivity vanishes. The resistance due to this effect is tiny compared with that of non-superconducting materials, but must be taken into account in sensitive experiments. ==Introduction== In the method described here a magnetic field is swept across the superconductor in a magnetic wave. This field induces current according to Faraday's law of induction. As long as the direction of motion of the magnetic wave is constant then the current induced will always be in the same sense and successive waves will induce more and more current. Traditionally the magnetic wave would be generated either by physically moving a magnet or by an arrangement of coils switched in sequence, such as occurs on the stator of a three-phase motor. Flux Pumping is a solid state method where a material which changes magnetic state at a suitable magnetic ordering temperature is heated at its edge and the resultant thermal wave produces a magnetic wave which then magnetizes the superconductor. A superconducting flux pump should not be confused with a classical flux pump as described in Van Klundert et al.’s review. The method described here has two unique features: *At no point is the superconductor driven normal; the procedure simply makes modifications to the critical state. *The critical state is not modified by a moving magnet or an array of solenoids, but by a thermal pulse which modifies the magnetization, thus sweeping vortices into the material. The system, as described, is actually a novel kind of heat engine in which thermal energy is being converted into magnetic energy. 抄文引用元・出典: フリー百科事典『 ウィキペディア（Wikipedia）』 ■ウィキペディアで「Flux pumping」の詳細全文を読む スポンサード リンク
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