The collider attracted worldwide attention last July when scientists revealed that they had located a particle with properties similar to a long-sought Higgs boson particle.
Although the LHC has now been shut down until 2015, the thousands of scientists, engineers and technicians involved will still be working while the collider undergoes a significant upgrade and consolidation.
A gigantic scientific instrument near Geneva, where it spans the border between Switzerland and France about 100 metres underground, the collider is run by CERN, the European Organization for Nuclear Research, and is used by scientists to study the smallest known particles: the fundamental building blocks of the universe.
Two beams of subatomic particles called ‘hadrons’ – either protons or lead ions – travel in opposite directions inside the circular accelerator, gaining energy with every lap. Physicists use the LHC to recreate the conditions just after the Big Bang, when the universe came into existence, by colliding the two beams head on at very high energy.
Teams of physicists around the globe then analyse data collected about the particles that are created, using special detectors.
The collider contains a vast assembly of different kinds of superconducting magnets that are able to conduct far larger electric currents than ordinary wire, creating intense magnetic fields more than 100,000 times greater than the Earth’s magnetic field to focus and accelerate the particles to high energies.
The magnetic fields are connected electronically to a carrying current between different magnets and, during the collider’s overhaul, more than 10,000 of the high current splices will be consolidated.
As well, the teams will open nearly 1,700 interconnections of the main magnets' cryostats – devices used to maintain the temperature at -271.3 degrees Celsius – while the tunnel ventilation system will also be replaced.
The particles generated in the LHC are made to collide at four different locations where the outcome of the collisions is recorded by the detectors, essentially giant cameras taking pictures millions of times a second.
The four locations mean four different experiments can be conducted by scientific teams ranging from 500 to 3,500 individuals depending on what is being done.
Two experiments – ATLAS and CMS – are general-purpose discovery experiments and these will also undergo maintenance and upgrade to meet the machine’s new environment in two years' time.
The ATLAS Collaboration involves 3,500 scientists from 178 institutes around the world and is one of the largest joint enterprises by physicists among all the LHC experiments
When the collider is switched back on for the next phase, scientists hope to uncover explanations regarding other mysteries of nature, such as yet-undiscovered ‘super-symmetric partners’, the evidence of dark matter candidates and the existence of extra dimensions of space.
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