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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."
Sorry. The last I checked, the record went to the Bose-Einstein condensate at a few nano-Kelvin. 1.9 K is boiling by comparison.
Just callin' it like I see it.
Already done www.lhcountdown.com
LHC Countdown
If the magnets are superconducting, why would they need a good thermal conductor? It's not as if superconductors generate any heat in operation.
That's an excellent question. I'm guessing they are not using HTC superconductors, which can be cooled with liquid nitrogen, due to the potential for current-induced superconductivity breakdown.
Here's a little background on the effect (Thank you Wikipedia...)
This equation, which is known as the London equation, predicts that the magnetic field in a superconductor decays exponentially from whatever value it possesses at the surface. The Meissner effect breaks down when the applied magnetic field is too large. Superconductors can be divided into two classes according to how this breakdown occurs. In Type I superconductors, superconductivity is abruptly destroyed when the strength of the applied field rises above a critical value Hc. Depending on the geometry of the sample, one may obtain an intermediate state consisting of regions of normal material carrying a magnetic field mixed with regions of superconducting material containing no field. In Type II superconductors, raising the applied field past a critical value Hc1 leads to a mixed state in which an increasing amount of magnetic flux penetrates the material, but there remains no resistance to the flow of electrical current as long as the current is not too large. At a second critical field strength Hc2, superconductivity is destroyed. The mixed state is actually caused by vortices in the electronic superfluid, sometimes called fluxons because the flux carried by these vortices is quantized. Most pure elemental superconductors, except niobium, technetium, vanadium and carbon nanotubes, are Type I, while almost all impure and compound superconductors are Type II.
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.
1.9 Kelvin isn't that cold, and if the BBC are so excited about the temperature then they should check out pretty much any magnetism lab on the planet and they'll probably find colder spots than this! They were excited last week about energy from nothing (8 & 9th paragraphs).
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No. Superconductors generate exactly ZERO ohmic heating when current passes through them.
Not "some", but absolutely ZERO heating.
The LHC is being built by the European Organization for Nuclear Research (CERN), and lies under the Franco-Swiss border near Geneva, Switzerland.
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!
http://www-hep.phys.cmu.edu/cms/PICT_ARCH/lhc_map.gif
Its about 90% under France.
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
Weeell, it is the biggest cryogenic installation ever, the most complex machine ever built, the largest and most powerful particle accelerator ever, and they're pushing lots of data handling limits, such as network transfer speed, storage space and CPU cycles used. Now, what did I forget?
Its Schwarzchild radius would be a few cm. Although it would exert a force of 1 g if you were one Earth radius away (6000 km) but if we manage to make an Earth-weight black hole it will be a triumph of miniaturization. We will have succeeded in finally making a black hole small enough to fit in your pocket.
light does not stop accelerating at 186,000 mps, it travels at 186,000 mps (well... approximately) in a vacuum. it does not accelerate, it travels at a constant speed (as far as we know), so c is a constant. Now it does slow down as it travels through a medium (water, air, crystal), but mostly that is caused by the absorption and re-emmitance (is that a word?) of the photons.
Sorry, teleporters just kill you and then make a copy. A perfect, soul-less copy.
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.
I did say "with some caveats in strong magnetic fields" :)
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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).
Depends on your point of view. The *apparent* speed of light (group velocity - that is, the speed of wave propagation) in a medium is variable, but individual photons have zero mass, thus *can not* experience acceleration. In terms of basic classical physics, a=F/m, m is 0 - division by zero, the equation is unsolvable, i.e. the concept simply does not apply.
Nobody expects the British Columbia Human Rights Tribunal.
It just puts into perspective that there needs to be a risk benefit standard. Now if they said there was a one in a million chance of making a black hole the size of a basketball then I'd be saying it wasn't worth the risk.
As a reasonably modern person you would expect to benefit from advances made by research into physics. That is why the risk might be acceptable to you. Somebody who has a different lifestyle might have a different perspective on this.
there's that chance says that there is zero chance of it lasting more than a few milliseconds.
Nobody really knows what happens to microscopic black holes. There is no experimental evidence.
http://michaelsmith.id.au
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.
Spontaneous fluctations in magnitude of more than several degrees are HIGHLY improbable (as in "unlikely to happen during the Universe's lifetime").
However, different equipment failures can happen. That's why cables are cooled slightly below the boiling point of helium. Which itself is well below the critical temperature for Nb-Ti and Nb superconductors.
Caveat emptor is not english either. Caveat is latin for warning. See Wikipedia. So when someone says "with some caveats in strong magnetic fields" it is technically incorrect. Since "with some warnings in strong magnetic fields" isn't what he intended to say. However, caveat can be used correctly on its own. E.g. He entered the cave dispite his companion's caveat.
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Big deal.
We regularly go down below 50 millikelvin in an ADR (adiabatic demagnetization refrigerator). We can only measure down to 50, but we know that it is getting cooler than that.
That is 0.050 degrees above absolute 0...