Hot density rocks
From CERN article:
"There are many very dense and very hot questions to be addressed with the ion run..."
With the Large Hadron Collider's (LHC's) refit and restart accomplished, the records just keep tumbling. CERN has announced the highest-energy ion collision ever. The data generated by the experiment is going to take time and supercomputers to analyse, but CERN says the two lead ions slammed into each other at more than 1 Peta …
That sounds like a discussion of politics here in the States lately... "dense and hot".
Ok.. seriously question. Since they're generating "temperatures about a quarter of a million times those at the core of the sun.” and they want to go higher on the energy levels, how can they keep the temperature at the collision point from damaging the inside of the collider? I understand there's liquid hydrogen for cooling but even for a micro-second, that's a lot of energy to be dissipated.
We're talking pairs of atoms, not handfuls of the stuff, and probably not even nanoseconds of time.
Localised energy may be incredibly high, but it's localised to a very very tiny volume and lasts a very very short time.
The liquid helium cooling is so the superconducting magnets, well, you know... superconduct.
"how can they keep the temperature at the collision point from damaging the inside of the collider"
Note that 1 electron-volt equals 1.6x10^-19 joules. A single 1 peta-electron-volt (1x10^15 eV) blast amounts to about 1.6/10,000th of a Joule, and they're infrequent. If you manage to achieve 10,000 collisions per second, then the interior of the machine would have to deal with 1.6 Watts of heating. The massive vacuum casing and magnets probably won't notice 1.6 Watts.
However, the peta-volt collisions appear to be counted individually at this point, so you're probably not going to get full Watt-level heating.
From what I've read of the LHC configuration [but please bear in mind, it's 30 years since I studied physics to A-Level], there are a couple of answers to your question...
Firstly, the "ring" that is used to accelerate the particles [well, OK, in fact it is actually 2 rings, one on top of the other, and with the contained particles traveling in opposite directions] is super-cooled in order to allow the magnets that contain the particles to get benefits from super-conductivity [i.e. to maximise field strength]. This means that when the particles are "just circling" they are not, in fact, colliding with anything at all, just zipping along through a vacuum...
Secondly, when the particles are allowed to collide - and the computers that govern the ring control whether or not this happens - the collisions can only occur at the location of the various experiments [ATLAS, CMS] that are positioned around the ring itself.
Now for the tricky part...
If you take two identical cars and set each to travel at 30mph until they meet in a head-on collision, the result of the impact is that both cars should [all things being equal] stop dead on the spot of the collision, because the respective kinetic energy each car brings to the collision would be exactly cancelled out by the other vehicle. The resultant energy is released as heat, [infra-red] light, and sound [and the gasps of insurance under-writers]. Point being that the two cars stop, or, if they do continue to move, it is at a fraction of their original speed and with a fraction of their original energy...
So now lets go back to ATLAS and CMS... Inside the huge chambers that house these experimental sensors, the environment is set up so that the high energy particles travel through the matter of the sensor, leaving a wake of interactions [with the sensor] as they go. Each interaction essentially robs a bit more energy from the particle, until it decays naturally [which is the way these particles behave, given their latent instability].
OK, we got as far as slow-moving particles... Because they are moving much more slowly now, and because their lifespan can be measured in millionths, billionths or even trillions of a second, they literally don't have time to travel beyond the physical confines of the detector before they literally disappear through decay.
So that's why the LHC doesn't melt itself...
I'll say it again: I'm not a physicist and I've only got a basic understanding from reading reports and articles from science journals and tech news sites like this one. Your mileage may vary [YMMV].
“At that temperature, matter becomes a strange thing called a quark-gluon plasma, not seen in nature since the universe's age was measured in microseconds.”
Is that true? I can’t believe that it took a human-made collider on Earth to achieve what was impossible for the last 14 billion years.
Ultra high energy cosmic rays can exceed this energy level. The "Oh-My-God particle" had an energy of approximately 3x10^20 electron volts. However the energy released in a single collision of such a particle with a stationary proton or neutron is much lower at about 7.5x10^14 electron volts. An (exceedingly unlikely) head on collision of 2 such such particles would release more energy than could be produced in any man made accelerator (even one as big as the planet!!).
(For more information on the Oh-My-God particle see https://en.wikipedia.org/wiki/Oh-My-God_particle)
I am a little bit confused about that. The nuclear mass of the common lead isotope is 208, so wouldn't it be 416 nucleons colliding?
At the energies involved, the two nuclei look to one another like thin discs colliding face on, so I imagine it is possible that some of the nucleons just go straight through and out the other side and the figure of 208 is coincidental, but it seems oddly specific to the lead nucleus mass.
"the Wikipedia article seems to suggest only protons are involved"
It's only the protons that are charged so it's those on which the accelerator works. The neutrons are just along for the ride.
A car analogy - it's only the tyre contact patch that touches the road so it's that that gets accelerated and the rest of the car is just along for the ride.
Replying to myself, Chris Williams from the Reg has helpfully contacted me and as a result I now have the link to the CERN announcement.
The announcement is a bit badly worded, I think. It explains that the total energy is about a PeV (1045TeV), and that there are 208 nucleons in a lead nucleus. It then suddenly switches to writing about nucleon pair energies, which are roughly 1045/208 or about 5TeV, without explaining that each nucleon of each pair is from each of the colliding nuclei. It's easy to miss that it is 5TeV per pair and not per nucleon. The point is that the total collision energy is the sum of the energies of each nucleus, so they are accelerated to a "mere" 522.5TeV each.
So yes, there are 416 nucleons involved and the energy per nucleon is about 2.5GeV as I surmised.
Those of us in PETA NEVER harm animals. We raise them with tender loving care, then we kill them and eat them.
 That's "People Eating Tasty Animals", not the enviro-idiots "People Exterminating To Acquire"
 Seriously, look up PETA's record on euthanizing all the strays that get dumped on them by completely clueless idiots.
 Don't get me wrong ... I'm no fan of "no kill" shelters ... but the PETA folks make a profit off of the concept. Frankly, it's quite disgusting.
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