Naked Science Forum
Non Life Sciences => Physics, Astronomy & Cosmology => Topic started by: yamo on 06/11/2010 06:42:46
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What is a quench?
this sentence: The copper is there to take over carrying the enormous current if the superconductor heats up in a so-called quench and loses its superconductivity — but only for the 100 seconds or so that it takes for the magnets to dump their enormous and dangerous energy.
in this article: http://www.nytimes.com/2010/11/02/science/space/02cern.html?_r=1&sq=hadron&st=cse&scp=2&pagewanted=all
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Superconductivity depends on the superconductor being very cold (in this case liquid helium temperatures) it is also sensitive to magnetic fields(a bit difficult if you are making a magnet) at some point as the magnetic field rises even though the superconducting wire is kept very cold the magnetic field will cause the material to lose its superconducting properties. This then means that the part of the wire in the highest field stress develops resistance and heats up very quickly positive feedback that makes the situation worse embedding the fine and very brittle superconducting wires in a matrix of copper helps to stabilise this runaway effect and prevent a disastrous energy dump in one location . Big accelerators using superconducting magnets and trying to reach the very highest energise run very close to this magnetic field limit and so run the risk of this sudden failure of superconductivity which is called a quench. The term quench as well as being used to describe the relieving thirst is often used in a technical sense to describe a sudden changing of the properties of a material. Another use is putting red hot metals into cold water to fix their crystal properties and harden steel.