Question: Is it true that they are/have created/modified the LHC to make it more efficient? If so how?

Flavia de Almeida Dias answered on 7 Nov 2015:

Hello!

The initial design of the LHC was for it to operate at a energy of 14 TeV (which is 7 times more energetic than the Tevatron, which was the previous biggest collider in the world). However, when developing projects which are in essence the frontier of knowledge and technology, there are a lot of things which can behave not quite as expected. One of them was turning the LHC on at the energy that we planned.

To be able to accelerate the protons at such high energies, we need a very large magnetic field. To produce very large magnetic fields, instead of using permanent magnets (like the ones we put on the fridge), we use the property that an electrical current produces magnetic field. If you have learned Ohm’s law before, you might remember that the electric current i = V/R, where V is the potential measured across your conductor and R is the resistance of the conductor material. Therefore, if a material has a lot of resistance, when you put a potential different into it, a lot of the energy will be dissipated as heat. If the material has low resistance, it can transport the energy in the electric current more efficiently. However, for such high magnetic fields as the ones used by the LHC, we need the current generated to be so high that the wires carrying it needs to have zero resistance! A few materials have such property under certain conditions (usually at very low temperatures), and these materials are called superconductors.

Superconductors are very cool (literally, at the LHC they are at -271 Celsius, which is colder than outer space!). But besides been cool, they are also very hard to deal with. To perform like we want them to, they need what we call training – just like your dog, to make hard tricks, need to train for a long time. When you assemble something for the first time ever, you don’t quite know exactly how it will react – despite testing all of the individual pieces one by one, it doesn’t mean the final assembled product will behave perfectly. In our case, we realised when we assembled the LHC, that the magnets needed more training than we first predicted to reach high energies. So when we first turned it on, we did so with half of the design energy (7 TeV – 2010). In the following years (2011-2012), we increased the energy a little bit (8 TeV), and now, in 2015, we have turned it on with energy of 13 TeV – almost the design energy of 14 TeV. We have improved a lot of our systems and methods since we first turned the LHC on, so we can now run at much higher energy.

Another planned upgrade of the LHC is what we call the High-Luminosity LHC. If this happens, it should start around 2024, and the biggest advantage with respect to the current LHC is that it can accumulate about 10x more information in the same amount of time.