Engineering the Large Hadron Collider

The Structure and Function of the World’s Largest Machine

Oct 6, 2008 Susan Kristoff

The Large Hadron Collider is the world's largest machine, used to learn more about the tiniest particles of matter.

In September 2008, the first electron beams were shot around the Large Hadron Collider, or LHC. The LHC is the world’s largest particle accelerator, built by an international consortium and managed by CERN, the European Center for Nuclear Research.

The LHC system consists of two major components: the accelerator tunnel and pathway and the particle detection system.

LHC Accelerator Tunnel System

The LHC tunnel forms a circle roughly 27 km in circumference that straddles the border between Switzerland and France at a depth of about 100 m. Inside the tunnel, two pipelines are used to move two separate streams of electrons around the LHC in opposite directions. The pipelines themselves are cooled to 1.9 degrees Kelvin using liquid helium, and operate in a vacuum that is similar to interstellar space.

The electron beams are moved and controlled through vast arrays of superconducting magnets. These powerful magnets are strong yet precise, accurately guiding the streams around the accelerator and then nudging them close enough for collisions within the particle detectors. When the accelerator is working at full speed, the streams will be traveling at nearly the speed of light. About 9600 magnets of different types are used in the LHC.

LHC Particle Detection System

The particle detectors are designed to capture information about what happens when collisions occur between the electron streams, at rates of up to 600 million collisions per second. There are six different detectors around the ring of the LHC, and each is designed to detect different types of particles and events. The detectors include:

  • ATLAS and CMS, general purpose detectors
  • ALICE, to study quark-gluon plasma
  • LHCb, to study b-quarks
  • TOTEM, to study protons involved in glancing collisions, rather than head on collisions
  • LHCf, to create and study cosmic waves

A detector records information about the particles that pass through it, and is made up of different components that depend on the type of particles and behavior to be detected. Some basic detector components include:

  • Tracking Device – Uses a magnetic field to deflect the particle as it passes through it. The curvature of the particle’s path provides information on the momentum of the particle, which can in turn be used to identify the type of particle. This is most often use to detect muons.
  • Electromagnetic Calorimeter – Measures the energy of light particles as they interact with other particles
  • Hadronic Calorimeter – Measures the energy of hadrons as they interact with other particles.
  • Particle Identification Detector – Detects radiation generated by particles, which can be used for particle identification

The combination of all of these components makes the LHC the world’s largest and most complex machine. Precise design, implementation, and operation result in the ability to collect information on the smallest known particles and the highest-energy operations.

Sources

CERN website

CERN FAQ PDF – LHC: The Guide

The copyright of the article Engineering the Large Hadron Collider in Engineering is owned by Susan Kristoff. Permission to republish Engineering the Large Hadron Collider in print or online must be granted by the author in writing.
Installing one of the LHC particle detectors., Square87 - Wikimedia Commons Installing one of the LHC particle detectors.
Simulation of LHC operation., CERN Simulation of LHC operation.
 
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