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

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Featured updates on this topic

5 Apr 2015 – After two years of intense maintenance and consolidation the Large Hadron Collider is back in operation

17 Mar 2015 – Today the ATLAS and CMS experiments presented for the first time a combination of their results on the mass of the Higgs boson

13 Feb 2015 – Two years ago, CERN's accelerators and experiments shut down for maintenance, to prepare the LHC for running at 13 TeV

27 Jan 2015 – Recent publications from CMS use data from the LHC's first run to shed light on the properties of the Higgs boson

Updates

5 May 2015 – This morning, for the first time in two years, proton-proton collisions were delivered to the LHC experiments at injection energy: 450 GeV per beam

10 Apr 2015 – Last night the LHC operations team successfully circulated a beam at 6.5 TeV - one of many steps before the LHC can deliver collisions to experiments

9 Apr 2015 – With proton beams back in the LHC, operations experts have weeks of work to do before they can collide beams in experiments at the energy of 13 TeV

2 Apr 2015 – The first beams could be circulating in the machine sometime between Saturday and Monday

1 Apr 2015 – Physicists at the European Laboratory for Particle Physics announced today that an invisible Force permeates the universe, binding the galaxy together

26 Mar 2015 – A short circuit in a superconducting dipole magnet is delaying the beam injection in the LHC. Teams are working around the clock to fix the issue

12 Mar 2015 – Watch CERN engineers explain the work during the laboratory's long shutdown to prepare the LHC for running at 13 TeV

9 Mar 2015 – Particles were successfully injected into the LHC last weekend, passing through three sectors of the accelerator.

6 Mar 2015 – The Operations team is testing the systems that deliver beams to the Large Hadron Collider in preparation for the start-up this month

23 Feb 2015 – Watch a timelapse video of the huge LHC detectors ALICE, ATLAS, CMS and LHCb preparing to start up again