I think that analogy is also used with fusion, either that or the putt-putt volcano analogy :v:
[QUOTE=Krinkels;45197135]The whole 'cooldown' thing had me really confused, since most things heat up in use and need to cool down to avoid damage, whereas this needs to cool down for use.[/QUOTE]
The particle beams that the LHC create need to be steered in that circle and also kept on target. You can do this with magnetic fields. The comparatively "simple" way to create the very strong fields required in a particle collider is to use superconducting electromagnets. [URL="http://en.wikipedia.org/wiki/Superconductivity"]Superconductivity[/URL] is a property displayed by exceptionally cold materials, where the electrical resistance very suddenly drops from it's normal value to zero. I don't mean "immeasurably close to zero" I mean exactly zero. Electrical currents flowing through a superconductor loose no energy. So a piece of superconductor can be closed into a loop, and the electricity will simply flow around and around it forever, never needing to be topped up. The electrical current flow creates a magnetic field, which will remain permanent as long as the whole superconductor remains cold enough. Most materials will only superconduct at a few kelvin/degrees Celsius (same difference, literally) above absolute zero, and the only cryogenic fluid capable of the job is (expensive) liquid helium (liquid nitrogen simply isn't even close to cold enough).
The same technology sees a more familiar use in MRI machines.
(There are "high temperature" superconductors too, which 'only' need to be cooled to about −135 °C, which IS within the capability of liquid nitrogen. The LHC doesn't use these.)
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