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Comment by SiempreViernes | Hacker News Reader

Man, so relieved it's just cooling one section that is meant by "major consequences", title made me think of the explosion during commissioning. Looks like it's only sector S78 that needs attention: https://op-webtools.web.cern.ch/vistar/vistars.php?usr=LHC2

This report is impressively detailed for being put out just two days of the incident, but I guess LHC having world class technical diagnostics teams is not too surprising.

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When I was visiting CERN, the whole accelerator was in maintenance mode. We have seen a detector (IIRC it was ATLAS) which was disassembled in layers, so we were able to see almost all of it.

Our guide explained that whole schedule for maintenance and operation is set in stone and whole schedule is planned almost to hour resolution for the next six months or so. Also it's worth noting that, there is periodic maintenance that needs to be done, and that's also planned in advance.

Because of this stringent requirements, "several weeks" of shift is indeed a major problem, and by several I guess they are looking to ~8 weeks, if not more.

My uncle, who is not a physicist, but "one smart mf", was one of the heads of the beam instrumentation team at Fermilab, and spent a large part of his career designing, building and maintaining detectors. It utterly blows my mind.

The "major consequences" seem to be for the schedule:

> This incident will probably have a great impact on the LHC schedule, with machine operation unlikely to resume for at least several weeks.

I also read it instantly in case they had a black hole on their hands, even though I'd expect us all to be dead almost instantly if any real "major consequence" event truly happened in the accelerators.

You can't create a black hole in LHC. Although sometimes when I read social media I wish they could.

Even if the tenth digit of pi can't be a six, it still might be a six, namely when you don't know it can't be a six because it is a three. Uncertainty is different from possibility.

This is just my personal opinion, but the mechanism that creates particles and black holes is the same. Meaning without throwing incredible mass at it, you won’t make a black hole. You can’t. You’ll make a particle or break apart one. Which is in fact what happens. There are also many natural events that resemble what the LHC does, at even greater energies and much greater mass, and yet no black holes. A black hole is dangerous because it’s a planet worth of mass in compact singularity. If it has no such mass it can’t do anything.

Putting this on a slightly stronger footing:

Black holes don't have to be enormous. We focus on the enormous ones because we know how they form from stars, but there's nothing inherent in black hole math to prevent tiny ones.

You can, in theory, create ones from energy, because mass and energy are the same. It's not impossible to create a tiny black hole in a collider.

Just not the LHC. It doesn't have anywhere near enough energy, even for the tiniest black hole. And even if there were some unexpected physics that did let a microscopic black hole form, it would instantly vaporize in a burst of Hawking radiation. (The smaller a black hole is, the faster it evaporates.)

If somehow all of that were wrong, and the LHC did create a tiny black hole with a lifetime longer than a yoctosecond, it could grow and become a real problem very quickly. But if you're inventing that much physics, you might as well just worry about the appearance of a mega-space-goat that eats the Earth, because it's equivalent levels of guessing.

I found a more detailed analysis here:

https://youtube.com/watch?v=Dp2C4J2yMe4

Apparently the probability is indeed very low.

"at least several weeks" is technically correct but I think a bit of an understatement. A sector takes about 3-4 weeks to warm up and 4-5 weeks to cool down. Then it needs to undergo powering tests and probably some "training" quenches.

Since the winter shutdown is scheduled for end of October (thanks to the energy crisis), there's a good chance we are finished with proton collisions for the year. If the leak can get fixed and the sector cooled down by mid/late September, we might have time for the heavy ion run. Last year's ion run was cancelled due to shortening the year, so 2 years in a row would not be great.

Is there any plan to migrate to higher temperature superconductors which might not require such low temperatures?

They introduce their own problems. They're typically brittle ceramics, making them hard to work with. They're more expensive to manufacture. And they have a lower critical current density (i.e. there's less current they can carry before losing superconductivity).

The Future Circular Collider is looking to switch to niobium-tin from LHC's niobium titanium. https://en.wikipedia.org/wiki/Future_Circular_Collider Unfortunately they'll still run at liquid helium temperatures-- while advanced superconductors have higher critical temperatures, the critical field (magnet strength) still goes higher as the magnet gets colder, and that's the figure of merit for collider designers. http://hyperphysics.phy-astr.gsu.edu/hbase/Solids/scbc.html

This is why you see new fusion reactor designs like the SPARC which use HTS superconductors throughout still use mildly exotic cryocoolants like liquid hydrogen-- not as expensive as liquid helium, but still better performing than liquid nitrogen. (Not to mention that liquid nitrogen is annoying in nuclear applications: it's easily activated by neutron radiation and deposits monoatomic carbon dust through your cryocooler circuit)

They would have written "Unforeseen Consequences" in that case ;-)

(https://developer.valvesoftware.com/wiki/Unforeseen_Conseque...)

A black hole is not unforseen, they don't call the place Black Mesa for nothing. But a resonant cascade, on the other hand...

> I also read it instantly in case they had a black hole on their hands, even though I'd expect us all to be dead almost instantly if any real "major consequence" event truly happened in the accelerators.

Idk why people think this. Black holes are not magic. They have exactly as much gravity as the mass had which collapsed into them.

As you go about your life right now the gravity of Switzerland is pulling you towards it a tiny bit. If due to some crazy event the mass of the whole country would collapse into a black hole that black hole would still tug you the same way and the same amount.

I’m not a physicist, but it seems like they’re a little magic, in that they’re so far from our normal experience, since gravity is proportional to the inverse square of the distance, and the distance to their center of mass is relatively very small, so you can get an extremely strong pull relative to a normal object of the same mass. It seems like even a very small black hole falling onto things could snowball, unless there’s something that counters that? Do black holes lose material/get less dense/evaporate under certain conditions?

Yes, black holes are theorized to evaporate due to Hawking radiation [0].

[0] https://en.wikipedia.org/wiki/Hawking_radiation

> Do black holes lose material/get less dense/evaporate under certain conditions?

They radiate something similar to heat (with wild possibilities for temperature).

>I'd expect us all to be dead almost instantly

Not an expert at all but from what I've read you'd expect wrong. Even if they could create a black hole out of the Matterhorn it would be so small, less than a hydrogen atom, that it doesn't interact much with anything.

"Even though a microscopic black hole might contain the mass of a mountain, it would experience almost no friction as it passed through regular matter. It would fall through regular material as if it wasn’t there." [0]

So the worst thing would be the missing Matterhorn which pretty sure would upset the Swiss.

[0]: https://www.universetoday.com/1930/are-microscopic-black-hol...

So… would it fall to the center of the Earth? At that point could it start consuming matter? I have to admit I’m very ignorant of how a small black hole could grow (or not).

Not saying I believe the LHC can make those or anything, just intrigued by the questions.

It’s so small at that point it begins to act a little like a white hole (Hawking radiation iirc?) and evaporates quickly. It’s surprisingly difficult for matter to cross an event horizon.

Edit-actually having a small black hole would unlock some truly sci-fi sounding tech. Like the fastest interstellar travel, seemingly unlimited power, etc.

If they manage to create one with almost no velocity, it would keep falling through the Earth, down, up and down again, for either something between atoseconds or centuries, until it either explodes or hits enough matter to get big enough to matter.

Or, more realistically (as realistic as we can be talking about the LHC creating black holes, AKA, not realistic at all), it will be launched into space in some random direction.

You're leaving out evaporation. A black hole with the mass of a mountain would evaporate on the order of a second.

That would also release energy the equivalent of ~20M megatons of TNT, which is half a million times that of Tsar Bomba and around that of the KT event. The Swiss wouldn't be too upset about anything.

There was some hope at one point that something like the LHC might produce black holes, but not the type you're thinking of as massive gravity wells that form when stars collapse. It has been postulated that the early universe in the immediate aftermath of the Big Bang may have contained primordial black holes, and any that were large enough to still exist today might be a possible source of dark matter. Any formed in a particle collider would be particle mass, not star mass, and have the gravitational attraction of particles, and evaporate almost instantly due to Hawking radiation. They'd have been harmless, but if it had been possible, it would at least confirm they actually can exist and observing the decay would have been our only realistic hope of observing Hawking radiation likely at least in this century.

Vistar is so cool :)

Also, here's a public grafana I just found with temperature charts in S78 and a bunch of other cryo data: https://dash.web.cern.ch/d/iDRuWWHGz/sector-78-trend

Not that I can do anything very interesting with that particular bit of information, but I'm always happy to see open data. We could really use more of that in public science, and CERN is really doing a great job

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