The Large Hadron Collider: How It Measures The Collisions

Large Hadron Collider Animation

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The Large Hadron Collider, above, is designed to collide two counter rotating beams of protons or heavy ions. Proton-proton collisions are foreseen at an energy of 7 TeV per beam.

• The beams move around the LHC ring inside a continuous vacuum guided by magnets.

• The magnets are superconducting and are cooled by a huge cryogenics system. The cables conduct current without resistance in their superconducting state.

ATLAS

The Atlas is one of two general-purpose detectors at the LHC. It will investigate a wide range of physics, including the search for the Higgs boson, extra dimensions, and particles that could make up dark matter.

With the same goals in physics as CMS, ATLAS will record similar sets of measurements on the particles created in the collisions – their paths, energies, and their identities. However, the two experiments have adopted radically different technical solutions and designs for their detectors' magnet systems.

The main feature of the ATLAS detector is its enormous doughnut-shaped magnet system. This consists of eight 25‑m long superconducting magnet coils, arranged to form a cylinder around the beam pipe through the centre of the detector. During operation, the magnetic field is contained within the central cylindrical space defined by the coils.

More than 1700 scientists from 159 institutes in 37 countries work on the ATLAS experiment.

ATLAS detector
• Size: 46 m long, 25 m high and 25 m wide. The ATLAS detector is the largest volume particle detector ever constructed.
• Weight: 7000 tonnes
• Design: barrel plus end caps
• Location: Meyrin, Switzerland.

Compact Muon Solenoid

The Compact Muon Solenoid (CMS) experiment uses a general-purpose detector to investigate a wide range of physics, including the search for the Higgs boson, extra dimensions, and particles that could make up dark matter. Although it has the same scientific goals as the ATLAS experiment, it uses different technical solutions and design of its detector magnet system to achieve these.

The CMS detector is built around a huge solenoid magnet. This takes the form of a cylindrical coil of superconducting cable that generates a magnetic field of 4 teslas, about 100 000 times that of the Earth. The magnetic field is confined by a steel 'yoke' that forms the bulk of the detector's weight of 12 500 tonnes. An unusual feature of the CMS detector is that instead of being built in-situ underground, like the other giant detectors of the LHC experiments, it was constructed on the surface, before being lowered underground in 15 sections and reassembled.

More than 2000 scientists collaborate in CMS, coming from 155 institutes in 37 countries.

CMS detector
• Size: 21 m long, 15 m wide and 15 m high.
• Weight: 12 500 tonnes
• Design: barrel plus end caps
• Location: Cessy, France. See CMS in Google Earth.