Topic

The Large Hadron Collider

The Large Hadron Collider (LHC) is the world’s largest and most powerful particle accelerator. It first started up on 10 September 2008, and remains the latest addition to CERN’s accelerator complex. The LHC consists of a 27-kilometre ring of superconducting magnets with a number of accelerating structures to boost the energy of the particles along the way.

Inside the accelerator, two high-energy particle beams travel at close to the speed of light before they are made to collide. The beams travel in opposite directions in separate beam pipes – two tubes kept at ultrahigh vacuum. They are guided around the accelerator ring by a strong magnetic field maintained by superconducting electromagnets. The electromagnets are built from coils of special electric cable that operates in a superconducting state, efficiently conducting electricity without resistance or loss of energy. This requires chilling the magnets to ‑271.3°C – a temperature colder than outer space. For this reason, much of the accelerator is connected to a distribution system of liquid helium, which cools the magnets, as well as to other supply services.

The Large Hadron Collider is the world's largest and most powerful particle accelerator (Image: CERN)

Thousands of magnets of different varieties and sizes are used to direct the beams around the accelerator. These include 1232 dipole magnets 15 metres in length which bend the beams, and 392 quadrupole magnets, each 5–7 metres long, which focus the beams. Just prior to collision, another type of magnet is used to "squeeze" the particles closer together to increase the chances of collisions. The particles are so tiny that the task of making them collide is akin to firing two needles 10 kilometres apart with such precision that they meet halfway.

All the controls for the accelerator, its services and technical infrastructure are housed under one roof at the CERN Control Centre. From here, the beams inside the LHC are made to collide at four locations around the accelerator ring, corresponding to the positions of four particle detectorsATLAS, CMS, ALICE and LHCb.

 

 

Technicians get around the tunnel on bicycles

Facts and Figures [PDF]

How many kilometres of cables are there on the LHC? How low is the pressure in the beam pipe? Discover facts and figures about the in the handy LHC guide

Download the LHC guide [PDF]

CERN firefighters during their daily safety training

Safety of the LHC

CERN takes safety very seriously. This report by the LHC Safety Assessment Group (LSAG) confirms that LHC collisions present no danger and that there are no reasons for concern

Read about the safety of the LHC

LHC

Virtual tour

Take a virtual tour of the Large Hadron Collider

Featured updates on this topic

11 Feb 2014 – A team composed of CERN staff, industrial support and mechanics from Pakistan have given access to the last LHC splice for inspection

25 Nov 2013 – When night falls over CERN, a team of X-ray experts go underground to perform tests on the Large Hadron Collider

Updates

17 Dec 2014 – The CERN cryogenics team are filling the LHC with liquid helium, cooling entire sections to below 4K

12 Dec 2014 – CERN teams are carrying out all required tests to get proton beams back in the LHC for March 2015

9 Dec 2014 – Magnets in one sector of the accelerator are fully prepared for the restart at higher energies

24 Nov 2014 – Weekend tests with beams brought protons just short of the LHC

20 Nov 2014 – The Open Data Portal makes data from real collision events at the LHC openly available to all

26 Sep 2014 – In CERN’s 60th year, the first proof of the existence of the Higgs boson earns a Guinness World Record for CERN, ATLAS and CMS

4 Aug 2014 – A team is on call 24 hours a day to monitor technical systems and quickly respond to alerts across CERN's accelerator complex

27 Jun 2014 – In preparation for the LHC's next run, physicists are calibrating the ATLAS experiment - with high-energy rays from outer space

23 Jun 2014 – Cool down of the Large Hadron Collider has already begun in preparation for research to resume early in 2015

23 Jun 2014 – Results reported by ATLAS and CMS discuss the decay of Higgs bosons directly to fermions, the particles that make up matter