Cryotron
Encyclopedia
The cryotron is a switch that operates using superconductivity
. The cryotron works on the principle that magnetic field
s destroy superconductivity. This simple device consists of two superconducting wires ( e.g. tantalum and niobium) with different critical temperature (Tc). A straight wire of tantalum
( having lower Tc) is wrapped around with a wire of niobium
in a single layer coil. Both wires are electrically isolated from each other. When this device is immersed in a liquid helium
bath both wires become superconducting and hence offer no resistance to the passage of electric current. Tantalum in superconducting state can carry large amount of current as compare to its normal state. Now when current is passed through the niobium coil (wrapped around tantalum) it produces a magnetic field, which in turn reduces (kills) the superconductivity of the tantalum wire and hence reduces the amount of the current that can flow through the tantalum wire. Hence one can control the amount of the current that can flow in the straight wire with the help of small current in the coiled wire. We can think of the tantalum straight wire as a "gate" and the coiled niobium as a "control".
A planar cryotron was developed in 1957 by Dudley Allen Buck
at Massachusetts Institute of Technology, made of thin films of lead and tin. This was one of the first integrated circuits, although using superconductivity rather than semiconductivity. In the next few years a demonstration computer was made and arrays with 2000 devices operated. A short history of this work is in the newsletter of the IEEE History Center, number 75, November 2007.
Superconductivity
Superconductivity is a phenomenon of exactly zero electrical resistance occurring in certain materials below a characteristic temperature. It was discovered by Heike Kamerlingh Onnes on April 8, 1911 in Leiden. Like ferromagnetism and atomic spectral lines, superconductivity is a quantum...
. The cryotron works on the principle that magnetic field
Magnetic field
A magnetic field is a mathematical description of the magnetic influence of electric currents and magnetic materials. The magnetic field at any given point is specified by both a direction and a magnitude ; as such it is a vector field.Technically, a magnetic field is a pseudo vector;...
s destroy superconductivity. This simple device consists of two superconducting wires ( e.g. tantalum and niobium) with different critical temperature (Tc). A straight wire of tantalum
Tantalum
Tantalum is a chemical element with the symbol Ta and atomic number 73. Previously known as tantalium, the name comes from Tantalus, a character in Greek mythology. Tantalum is a rare, hard, blue-gray, lustrous transition metal that is highly corrosion resistant. It is part of the refractory...
( having lower Tc) is wrapped around with a wire of niobium
Niobium
Niobium or columbium , is a chemical element with the symbol Nb and atomic number 41. It's a soft, grey, ductile transition metal, which is often found in the pyrochlore mineral, the main commercial source for niobium, and columbite...
in a single layer coil. Both wires are electrically isolated from each other. When this device is immersed in a liquid helium
Helium
Helium is the chemical element with atomic number 2 and an atomic weight of 4.002602, which is represented by the symbol He. It is a colorless, odorless, tasteless, non-toxic, inert, monatomic gas that heads the noble gas group in the periodic table...
bath both wires become superconducting and hence offer no resistance to the passage of electric current. Tantalum in superconducting state can carry large amount of current as compare to its normal state. Now when current is passed through the niobium coil (wrapped around tantalum) it produces a magnetic field, which in turn reduces (kills) the superconductivity of the tantalum wire and hence reduces the amount of the current that can flow through the tantalum wire. Hence one can control the amount of the current that can flow in the straight wire with the help of small current in the coiled wire. We can think of the tantalum straight wire as a "gate" and the coiled niobium as a "control".
A planar cryotron was developed in 1957 by Dudley Allen Buck
Dudley Allen Buck
Dr. Dudley Allen Buck was an electrical engineer and inventor of components for high-speed computing devices in the 1950s. He is best known for invention of the cryotron, a superconductive computer component that is operated in liquid helium at a temperature near absolute 0...
at Massachusetts Institute of Technology, made of thin films of lead and tin. This was one of the first integrated circuits, although using superconductivity rather than semiconductivity. In the next few years a demonstration computer was made and arrays with 2000 devices operated. A short history of this work is in the newsletter of the IEEE History Center, number 75, November 2007.
History
- December 1953 The magnetically controlled switch is proposed in Dudley Allen BuckDudley Allen BuckDr. Dudley Allen Buck was an electrical engineer and inventor of components for high-speed computing devices in the 1950s. He is best known for invention of the cryotron, a superconductive computer component that is operated in liquid helium at a temperature near absolute 0...
notebook. - July 1955 Dudley A. Buck application for U.S. Patent 2,832,897 Magnetically Controlled Gating Element
- August 1955 Lincoln Laboratory Memorandum 6M-3843The Cryotron - A Superconductive Computer Component
- 1956 A Cryotron Catalog Memory System by Al Slade and Howard McMahon
- 1957 James W. Crowe application for U.S. patent 3,100,267 Superconducting Gating Devices