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(krī`ōtrŏn'), magnetically controlled electronic switching device that operates at extremely low temperatures; it is designed to supplant, in part, the transistor in special electronic equipment (e.g., the computer). One type of cryotron consists of a straight wire (the gate) around which a wire coil (the control coil) is wound. Kept at temperatures near absolute zero, both wires become superconductors (see low-temperature physicslow-temperature physics,
science concerned with the production and maintenance of temperatures much below normal, down to almost absolute zero, and with various phenomena that occur only at such temperatures.
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; superconductivitysuperconductivity,
abnormally high electrical conductivity of certain substances. The phenomenon was discovered in 1911 by Heike Kamerlingh Onnes, who found that the resistance of mercury dropped suddenly to zero at a temperature of about 4.
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), but when current is passed through the coil, a magnetic field is induced that causes the gate to lose its superconductivity, thus switching off the current through it. Another type of cryotron uses conducting films in place of the wires to increase the switching speed. The cryotron is so minute that many of these devices can be packed into a very small area, thereby greatly increasing the degree of control.



a cryogenic switching element based on the property of semiconductors to abruptly change their conductivity under the influence of a critical magnetic field. The operation of a cryotron is analogous to that of a key or a relay; a cryotron may exist only in one of two states (the superconducting state or a state of low conductivity).

Cryotrons may be of the wire-wound or crossed-film (flat) type. The design of a film cryotron is shown in Figure 1. Cryotrons are capable of very fast response (the time of transition from one state into another is fractions of a microsecond); they are small (up to several thousand units per sq cm), inexpensive to produce, and highly reliable. As of 1973, because of engineering difficulties related to cryogenic cooling, cryotrons were at the stage of laboratory studies and experimental models.

Figure 1. Crossed-film cryotron: (1) control film (Pb), (2) insulating layer (SiO2), (3) gate film (Sn), (4) insulating layer (SiO2), (5) ground plane, (6) substrate, (Ic) control electric current, (Ig) gate electric current


Kraizmer, L. P. Ustroistva khraneniia diskretnoi informatsii, 2nd ed. Leningrad, 1969.



A switch that operates at very low temperatures at which its components are superconducting; when current is sent through a control element to produce a magnetic field, a gate element changes from a superconductive zero-resistance state to its normal resistive state.