I’ve just been reading about the Future Circular Collider (FCC) and I’m wondering just how big can you build these things? The FCC will have a circumference of 100 km, but could you build one with a circumference of 1000 km? How about one with a diameter of 1000 km? What are the restrictions on building these things? For example, do you need a geologically super-stable area? How about synchronising timings? How about the curvature of the Earth? What else? Or is it all just a matter of engineering and funding?
I doubt there are any limitations other than engineering and funding. The biggest issue for making it insanely large would probably be the amount of helium required to cool the superconducting magnets.
Yup, big ones cost more, just like big anything costs more. That’s pretty much all there is to it.
Do they actually need to use helium? Could they use other liquids instead and higher-temperature superconductors? For example liquid nitrogen or liquid neon with yttrium barium copper oxide or mercury barium calcium copper oxide? I know that the lower the temperature the better but is there a case for ‘good enough’?
Reading the Wiki on the FCC makes me think that they’re actually building a Turbo Encabulator.
It isn’t just the case that “the lower the temperature the better”; superconducting magnets have a “critical temperature” above which they are no longer superconducting, and putting enough energy into them to drive them can result in catastrophic thermal failure. Large magnets like those at CERN used on the Large Hadron Collider (LHC) actually have a two stage cooling system using an “insulating” outer jacket filled with liquid nitrogen at 77 K to minimize heat transfer to the inner dewer with liquid helium kept below at 1.9 K (liquid helium boils at 4.2 K and becomes superfluid at 2.1 K). Although helium has a low heat capacity it has very high thermal conductivity (as anyone who has dove breathing heliox can testify to) and in the superfluid state has essentially no internal viscosity, so even if you could keep some other substance from freezing long before getting down to that temperature it is ideal as a cryogenic coolant in every way save for cost.
It may be possible to use larger, higher temperature magnets but it would require a much larger accelerator and it would be far less precise, which means experimenters would get much less data per operating hour, which is a bad trade off in every conceivable way, notwithstanding the possibility that it may not be possible to collect sufficient data to ever draw definitive conclusions about particle interactions. Colliders are essentially the particle physics equivalent of catapulting rocks together and watching them occasionally collide in mid-air, and then examining pictures of the resulting dust and debris to figure out what minerals they are made of.
The only physical limit I can think of with a particle collider is being able to reject the amount of waste heat produced in order to keep magnets and power systems from failing. However, at very high energies the ‘cross section’ (potential for particle interaction) goes down, which means it has to run for much longer to get useful interactions. It just may not be worthwhile to build supermassive colliders unless there is also some way to power them without having to divert enough electricity to all of Europe, or else it might require a dedicated power generation system.
Ultimately, we’d like to discover some way to manipulate upon the nuclear forces directly without just smashing particles together in the same way we generate and use electricity without having to hand-crank a dynamo, but that will require new physics and the equivalent of the steam engine to drive it at power levels beyond what we can operate today, and that is nowhere on the horizon.
Stranger
Building across active tectonic plate boundaries would probably be a sub-optimal configuration.
Oh, come now. Turbo Encabulators are practically obsolete now, especially because the price point increases when powered by the modial interaction of the capacitive distractants and magneto-reluctance. Modern applications call for something like the Micro Encabulator. It uses three hydrocoptic marzel vanes instead of the usual six. Cite.
Relatedly, my question would be why should a particle collider be bigger? If we want higher energies, why not just apply more energy to the particles in the current collider?
That works for linear accelerators but they wind up being limited in how many times you can give the particle a “kick”.
Circular accelerators can apply a “kick” multiple times, however, the particles shed energy are they travel. The tighter the curve the more energy they shed so eventually the energy you put in matches that being given off and you top out. The larger the radius the more energy you can pump into the system hence the desire for bigger tracks.
Well, I just read a book where they made one that was orbital scale with the magnets in stable orbits and automatically aligned, so I suppose there’s no reason that we couldn’t build a really big one in space, outside of cost.
It isn’t phsically impossible bit as with everything done in space, it becomes vastly more complicated and expensive. Keeping seperate magnets in Earth orbit aligned to the necessary precision would require constant fine tuning to an absurd degree of precision due to both the lunar tides and mass concentrations in the Earth’s crust, and cooling the system would be significantly more difficult without a ready cold temperature reservoir.
On the other hand, you could build a linear accelerator of any practical desired length in solar orbit oriented with its axis pointing through the Sun, and with constant sunlight you could use giant orbiting solar arrays to power and shade the accelerator. At some point tidal forces would exceed the strength of any real world material but since we’re talking about somehow assembling and maintaining space structures thousands of kilometers in length I don’t think minor issues of material science are worth fiddling about.
Stranger
Let’s see, you want a big vacuum, cold, geologically stable. So the Moon’s the place!
But you can see what will happen. They start dumping waste radioactive material on the far side and the next thing you know it blows and up and sends the Moon off into space.
That’s actually what they did in the book, with one twist- there was no “structure”, under the assumption that the vacuum in space is better than one achievable on Earth, so they just had a series of magnet rings positioned just-so, and presumably very accurate station-keeping abilities (it wasn’t mentioned). And there was a sort of navigational red zone and beacons to keep unaware ships from sailing through an experiment.
I’m sorry but you will never convince me to use any type of Encabulator with an odd number of hydrocoptic marzel vanes. NEVER! :mad:
But empty space between magnets don’t buy you anything. An ideal space accelerator would still be a solid structure, made up of superconducting magnets placed as close as possible. So what do you gain from putting it in space? Digging a tunnel is far cheaper than launching it into space, even if you add the cost of vacuum pumps.
The Moon is only cold on the side facing away from the Sun. Although it could be buried under the lunar regolith, that just exacerbates the problems of lunar dust.
I’m not sure how that could be achieved because magnets at different orbital radii will orbit at different speeds. Of course, even a “solid” structure of such length isn’t going to be even approximately rigid and perturbations by Jupiter and other bodies. Another problem with space is that solar particle emissions will interfere with delicate instruments, requiring additional shielding.
Ultimately you’d be limited to less than 500 km of length for a linear accelerator. A circular accelerator could, in theory, have a diameter as large as 12,742 km, but the practicalites of geography would limit it. But then, the problems of alignment and powering a really large synchrotron are beyond the state of the art anyway, and at some point we’ll have to have develop magnets a several of orders of magnitude stronger than the 8.3 Tesla magnets used in the LHC to achieve much higher energies and luminosity.
Stranger
I’m not seeing the problem. Lunar dust is only a problem if you go outside. Once you’re underground there is no (surface) dust. And if we’re talking about engineering on such a large scale, it’s going to be a much smaller matter to clear the lunar spaceport and surrounds of dust.
What’s the physical difference between digging a massive, sealed, underground ring on the Moon vs. under the Earth?
Nothing.