The Large Hadron Collider | CERN
Description: 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.

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# 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 detectors – ATLAS, CMS, ALICE and LHCb.

# Facts and Figures [PDF]

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

### Download the LHC guide [PDF]

# Safety of the LHC

CERN takes safety very seriously. Thisreport 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

## Featured updates on this topic

### In pictures: Access to the last LHC splice

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

### X-ray tests: Night at the collider

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

### Technical troubleshooting at the CERN Control Centre

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

### Cosmic rays tune ATLAS for a particle symphony

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

### CERN announces LHC restart schedule

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

### CERN experiments report new Higgs boson measurements

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

### How universal is (lepton) universality?

3 Jun 2014 – New results from LHCb suggest that B+mesons decay to muons about 25% less often than they decay to electrons

### The tour continues for the Large Hadron Collider

23 May 2014 – Today the Collider exhibition, which began life at London’s Science Museum, launches in Manchester, UK, ahead of an international tour

### LHC consolidations: 27,000 shunts now in place

5 May 2014 – Some 27,000 electrical shunts have been added to connections between magnets on the LHC

### Tracking particles faster at the LHC

22 Apr 2014 – A new trigger system will expand what ATLAS scientists can look for during high-energy collisions at the Large Hadron Collider

### Microelectronics at CERN: from infancy to maturity

4 Mar 2014 – The start of the LAA project in 1986 propelled electronics at CERN into the era of microelectronics

### Highlights from CERN in 2013

19 Dec 2013 – Higgs boson decays, a Nobel prize for Higgs and Englert and a huge Open Days event were among the big stories at CERN this year

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