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One of the Coolest Places In the Universe
phantomflanflinger writes "The Cern Laboratory, home of the Large Hadron Collider, is fast becoming one of the coolest places in the Universe. According to news.bbc.co.uk, the Large Hadron Collider is entering the final stages of being lowered to a temperature of 1.9 Kelvin (-271C; -456F) — colder than deep space. The LHC aims to re-create the conditions just after the Big Bang and continue the search for the Higgs boson."
LHC Countdown
Because its not being built by Americans. It's being built by European Organization for Nuclear Research, A.K.A. 'CERN' (Conseil Europeen pour la Recherche Nucleaire). Thats why its not in the USA, and why its in France.
No. Superconductors generate exactly ZERO ohmic heating when current passes through them.
Not "some", but absolutely ZERO heating.
Indeed, getting 1.9K in a lab, or in a single NMR magnet is not a big deal. Try to do it with 1232 huge magnets, spread around 26.6 km, being some 100m underground, and using 7600 km of super-conducting "cable" (270 000 km of superconducting "strand"). This is roughly 4700 tons of material to keep at 1.9K, and 120 tons of helium being recirculated all the time through these stuff to assure 150 kW of HEAT power is dissipated. Noone ever has done a similar cryogenic installation at such scale before!
HTC technology is not available yet for applications like this. They are using conventional Sn3Ti (and NbTi to some extent) superconductors. I'm not sure how the Wikipedia quote is relevant here. Although the wires in LHC are made of LTS materials, the materials still are type II superconductors. The main reason to have large cooling capacity is a phenomenon called "quenching". The wires in the coils are actually made of really thin filaments of superconducting material inside a copper matrix. These filaments can (and do) go out of superconducting state because of a local problem, and at this small point there's naturally high ohmic heating. If the system can't respond quickly enough to lower the local temperature so that the superconducting state is restored, this point of normal state will start to spread at a high speed, causing more heating and boiling off the coolant quite expensively. So this is the reason why you need large cooling capacity and thermal conductivity.
U+F8FF
Nope. ANY superconductor has zero resistance. That's actually a part of definition for a superconductor.
Even high-temperature ones (with some caveats near critical temperature and in strong magnetic fields) have zero resistance.
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No. One more time: there's NO resistance. In one experiment, for example, there were no measurable current decrease in a magnet after 20 years.
Low-TC superconductors are preferable because they have much higher critical current. Superconductors lose their superconductivity when a high enough magnetic field is applied. This magnetic field can be external or generated by the current passing through the superconductor itself.
Oh, and 1.9K temperature is used because it has a margin of safety for liquid helium (which has 4K boiling point).
Oh, and 1.9K temperature is used because it has a margin of safety for liquid helium (which has 4K boiling point).
1.9 K is below the so-called "lambda point" of helium, which stands at 2.2 K. That point corresponds to a transition to the superfluid state. This may help with heat dissipation in this setup.