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Figure 1: People at work on the CMS detector open during the LS1
(Credit: CERN)

CMS is one of the four main experiments at the Large Hadron Collider at CERN.

Like ATLAS, CMS is a general purpose detector designed to investigate a wide range of physics including supersymmetry, extra dimensions and particles that could make up dark matter.

The scientific goals for the two experiments are the same, but they use different technical solutions. These similar science goals, but different designs allow the two experiments to cross-check results and confirm exciting discoveries such as a Higgs boson.

Quick facts

About the detector
Size 21m long, 15 m high and 15 m wide
Weight 12500 tonnes
Design Barrel plus endcaps
About the people
Collaboration 3820 people including physicists engineers, technicians, students and support staff
Number of institutes 182
Number of countries 42
Number of UK institutes 4

How does it work?

The CMS detector is built around a huge solenoid magnet. This takes the form of a cylindrical coil of superconducting cable that generates a field of 4 tesla (about 100,000 times the magnetic field of the Earth). The field is confined by a steel ‘yoke’ that forms the bulk of the detector’s 12,500-tonne weight.

How does CMS work
(Credit: CERN)

Unlike the other LHC experiments, CMS was constructed in 15 sections at ground level. Each section was lowered 100m into the underground cavern near Cessy in France and reassembled.

The dramatic descent of the central section of the CMS detector
(Credit: CERN)

The detector can be opened to allow maintenance and upgrade.

CMS is Moving
(Credit: CERN)

Last updated: 27 June 2019


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