How does the large Hadron collider work?

Question: How does the large Hadron collider work?
- Keywords:
  large hadron collider
Asked by anon-254693 on 15 May 2020.
- Tom Louth answered on 15 May 2020:
  
  I’m afraid I don’t work on the LHC, I know that there are couple of scientists on here who work at CERN so I would suggest you ask this question to them.
  
  Good luck!
- Ry Cutter answered on 15 May 2020:
  
  This is a big question. The LHC is a particle accelerator, lots of these exist around the world and are used for lots of different science (see https://en.wikipedia.org/wiki/List_of_accelerators_in_particle_physics for the list).
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  In particular, the LHC (as the name suggests) collides accelerated hadrons. These are baryons (protons and neutrons) and mesons. Which is a family of particles comprised of quarks! For the LHC, it is usually a beam of protons!
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  The collider itself is a giant ring made out of superconducting magnets. These magnets accelerate the protons, pushing them closer and closer to the speed of light. There are two beams of protons, each going in the opposite direction to the other. Once the protons are going fast enough they are made to collide!
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  The collision happens in front of a detector that is sensitive enough to detect a lot of high energy particles that fly out from the collision. This detector is so sensitive, the whole system has to be built underground, so cosmic rays from space don’t interfere with the experiment!
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  There’s a lot of complicated stuff going on, but that’s the basic gist of it 😀
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  Great question,
  Ry
- Susan Cartwright answered on 15 May 2020: last edited 15 May 2020 1:46 pm
  
  – Sigh – I wrote an answer to this (as a comment when it was only asked of Tom) but the system seems to have eaten it. If you didn’t see it before it vanished into a black hole, I’ll try to remember what I wrote! [Of course, having submitted my answer, I can now see my comment, which I couldn’t before! Never mind: now you’ve got the information twice, but with a more useful link!]
  
  There are basically two things that an accelerator has to do: it has to steer the particles where you want them to go, and it has to accelerate them to the energy you want. Both of these things are best done if there aren’t any annoying air molecules for the particles to bump into, so at the heart of any accelerator is a long tube (the beampipe) which has all the air pumped out of it. Then you use magnets to bend the paths of the particles – round in a circle for the LHC, but not all accelerators are circular – and electric fields to accelerate them. For more information, try CERN: https://home.cern/science/accelerators
- Joel Goldstein answered on 18 May 2020:
  
  The main aim of the LHC programme is to put as much energy as possible into a tiny region of space. At such high energy densities, the laws of physics are very different, and new forces and particles can appear – you can think of it as recreating the conditions in the universe about a billionth of a second after the big bang.
  
  To do this we take beams of subatomic particles (normally protons but sometimes heavier nuclei), accelerate them (i.e. give them lots of kinetic energy) and try to collide them head on into each other. We want the particles to have the highest energy we can reach (to get the most extreme collisions) and we need very intense beams to get the most collisions so we can observe very rare events.
  
  To do this, the LHC is one of the most complex machines ever built. The key components are:
  
  – an injection chain of smaller accelerators, that provide bunches of protons already travelling very close to the speed of light
  
  – a 27km long vacuum tube, in which the subatomic particles can circulate without bumping into air molecules
  
  – powerful magnets to steer the particles around the ring in the vacuum pipe, and to focus the beams to a tiny size (about the width of a human hair) to increase the intensity
  
  – accelerating cavities (a bit like giant microwave ovens) to add energy to the particles and push them closer and closer to the speed of light every time they pass through
  
  – one of the world’s largest cryogenic plants to provide liquid helium to the magnets, most of which need to be superconducting to get the high magnetic fields needed
  
  – four huge detectors, each bigger than a house and weighing thousands of tons but functioning like a supercharged digital camera, to record the collisions and analyse the data.
  
  The whole operation takes thousands of people, almost unimaginable amounts of computing (both at CERN and around the world) and as much electrical power as a small city. And quite a lot of money…
- Krishna Mooroogen answered on 2 Jun 2020:
  
  I’ll try to give a very small answer. Accelerators use very strong magnets to accelerate and guide particles to smash into each other, in a very small and precise area at very high energies. The bigger they are, the faster the particles can go and the bigger the smash. Scientists look at pieces left over from the smashing to discover what’s inside. However, accelerators can be used for lots of other science too, not just collisions.

Comments

Susan commented on 15 May 2020:

Basically, particle accelerators like the LHC have two main components: large magnets to focus the beams of particles and steer them in the right direction (round in a circle, for the LHC) and electric fields to accelerate the particles to the energies you want. The particles circulate in a “beam ppe”, which is maintained at a good vacuum so that the accelerated particles will not collide with gas in the beampipe and lose energy or be defocused. It is all rather complicated, and in particular the LHC relies on several smaller accelerators to get the protons up to a minimum energy before they are injected into the LHC itself. You might find it interesting to explore the “Accelerators and Detectors” section of “The Particle Adventure” website: see https://particleadventure.org/accelerators-and-detectors.html

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Question: How does the large Hadron collider work?