Large Hadron Collider (LHC) FAQ

Large Hadron Collider (LHC) FAQ

LHC FAQ 0406Geneva (ISJ) - The Large Hadron Collider (LHC) is the most powerful particle accelerator ever built. The accelerator sits in a tunnel 100 metres underground at CERN, the European Organization for Nuclear Research, on the Franco-Swiss border near Geneva, Switzerland.

What is the LHC?

The LHC is a particle accelerator that pushes protons or ions to near the speed of light. It consists of a 27-kilometre ring of superconducting magnets with a number of accelerating structures that boost the energy of the particles along the way.

Why is it called the ?Large Hadron Collider??

? "Large" refers to its size, approximately 27km in circumference

? "Hadron" because it accelerates protons or ions, which belong to the group of particles called hadrons

? "Collider" because the particles form two beams travelling in opposite directions, which are made to collide at four points around the machine

How does the LHC work?

? The CERN accelerator complex is a succession of machines with increasingly higher energies. Each machine accelerates a beam of particles to a given energy before injecting the beam into the next machine in the chain. This next machine brings the beam to an even higher energy and so on. The LHC is the last element of this chain, in which the beams reach their highest energies.

? Inside the LHC, two 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. Below a certain characteristic temperature, some materials enter a superconducting state and offer no resistance to the passage of electrical current. The electromagnets in the LHC are therefore chilled to 271.3�C (1.9K) ? a temperature colder than outer space ? to take advantage of this effect. The accelerator is connected to a vast distribution system of liquid helium, which cools the magnets, as well as to other supply services.

What are the main goals of the LHC?

The Standard Model of particle physics ? a theory developed in the early 1970s that describes the fundamental particles and their interactions ? has precisely predicted a wide variety of phenomena and so far successfully explained almost all experimental results in particle physics. But the Standard Model is incomplete. It leaves many questions open, which the LHC will help to answer.

How was the LHC designed?

Scientists started thinking about the LHC in the early 1980s, when the previous accelerator, the LEP, was not yet running. In December 1994, CERN Council voted to approve the construction of the LHC and in October 1995, the LHC technical design report was published.

Contributions from Japan, the USA, India and other non-Member States accelerated the process and between 1996 and 1998, four experiments (ALICE, ATLAS, CMS and LHCb) received official approval and construction work started on the four sites.

LHC FAQ02 0406What are the detectors at the LHC?

There are seven experiments installed at the LHC: ALICE, ATLAS, CMS, LHCb, LHCf, TOTEM and MoEDAL. They use detectors to analyse the myriad of particles produced by collisions in the accelerator. These experiments are run by collaborations of scientists from institutes all over the world. Each experiment is distinct, and characterized by its detectors.

What is the data flow from the LHC experiments?

The CERN Data Centre stores more than 30 petabytes of data per year from the LHC experiments, enough to fill about 1.2 million Blu-ray discs, i.e. 250 years of HD video. Over 100 petabytes of data are permanently archived, on tape.

How much does the LHC cost?

? Construction costs (MCHF ? Million Swiss Franc)




LHC machine and areas*




CERN share to detectors




LHC computing (CERN share)








*Includes: Machine R&D and injectors, tests and pre-operation

? Costs for Run 1

Exploitation costs of the LHC when running (direct and indirect costs) represent about 80% of the CERN annual budget for operation, maintenance, technical stops, repairs and consolidation work in personnel and materials (for machine, injectors, computing, experiments).

The directly allocated resources for the years 2009-2012 were about 1.1 billion CHF (Swiss Franc) per year.

? Costs for LS1

The cost of the Long Shutdown 1 (22 months) is estimated at 150 Million CHF (Swiss Franc). The maintenance and upgrade works represent about 100 MCHF for the LHC and 50 MCHF for the accelerator complex without the LHC.

What is the LHC power consumption?

The total power consumption of the LHC (and experiments) is equivalent to 600 GWh per year, with a maximum of 650 GWh in 2012 when the LHC was running at 4 TeV. For Run 2, the estimated power consumption is 750 GWh per year.

The total CERN energy consumption is 1.3 TWh per year while the total electrical energy production in the world is around 20000 TWh, in the European Union 3400 TWh, in France around 500 TWh, and in Geneva canton 3 TWh.

What are the main achievements of the LHC so far?

? 10 September 2008: LHC first beam

? 23 November 2009: LHC first collisions

? 30 November 2009: world record with beam energy of 1.18 TeV

? 16 December 2009: world record with collisions at 2.36 TeV and significant quantities of data recorded

? March 2010: first beams at 3.5 TeV (19 March) and first high energy collisions at 7 TeV (30 March)

? 8 November 2010: LHC first lead-ion beams

? 22 April 2011: LHC sets new world record beam intensity

? 5 April 2012: First collisions at 8 TeV

? 4 July 2012: Announcement of the discovery of a Higgs-like particle at CERN

Source: CERN

Image Source: CERN

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