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| title | chunk | source | category | tags | date_saved | instance |
|---|---|---|---|---|---|---|
| CERN | 3/8 | https://en.wikipedia.org/wiki/CERN | reference | science, encyclopedia | 2026-05-05T12:40:06.396246+00:00 | kb-cron |
The LHC tunnel is located 100 metres underground, in the region between Geneva International Airport and the nearby Jura mountains. The majority of its length is on the French side of the border. It uses the 27 km circumference circular tunnel previously occupied by the Large Electron–Positron Collider (LEP), which was shut down in November 2000. CERN's existing PS/SPS accelerator complexes are used to pre-accelerate protons and lead ions which are then injected into the LHC. Eight experiments (CMS, ATLAS, LHCb, MoEDAL, TOTEM, LHCf, FASER and ALICE) are located along the collider; each of them studies particle collisions from a different aspect, and with different technologies. Construction for these experiments required an extraordinary engineering effort. For example, a special crane was rented from Belgium to lower pieces of the CMS detector into its cavern, since each piece weighed nearly 2000 tons. The first of the approximately 5000 magnets necessary for construction was lowered down a special shaft at in March 2005. The LHC has begun to generate vast quantities of data, which CERN streams to laboratories around the world for distributed processing, making use of a specialized grid infrastructure, the LHC Computing Grid. In April 2005, a trial successfully streamed 600 MB/s to seven different sites across the world. In August 2008, the initial particle beams were injected into the LHC. The first beam was circulated through the entire LHC on 10 September 2008, but the system failed 10 days later because of a faulty magnet connection, and it was stopped for repairs on 19 September 2008. The LHC resumed operation on 20 November 2009 by successfully circulating two beams, each with an energy of 3.5 teraelectronvolts (TeV). The challenge for the engineers was then to line up the two beams so that they smashed into each other. This is like "firing two needles across the Atlantic and getting them to hit each other" according to Stephen Myers, director for accelerators and technology. On 30 March 2010, the LHC successfully collided two proton beams with 3.5 TeV of energy per proton, resulting in a 7 TeV collision energy. This was enough to start the main research program, including the search for the Higgs boson. When the 7 TeV experimental period ended, the LHC increased to 8 TeV (4 TeV per proton) starting March 2012, and soon began particle collisions at that energy. In July 2012, CERN scientists announced the discovery of a new sub-atomic particle that was later confirmed to be the Higgs boson. In March 2013, CERN announced that the measurements performed on the newly found particle allowed it to conclude that it was a Higgs boson. In early 2013, the LHC was deactivated for a two-year maintenance period, to strengthen the electrical connections between magnets inside the accelerator and for other upgrades. On 5 April 2015, after two years of maintenance and consolidation, the LHC restarted for a second run. The first ramp to the record-breaking energy of 6.5 TeV was performed on 10 April 2015. In 2016, the design collision rate was exceeded for the first time. A second two-year period of shutdown begun at the end of 2018.
=== Accelerators under construction === As of October 2019, the construction is on-going to upgrade the LHC's luminosity in a project called High Luminosity LHC (HL–LHC). This project should see the LHC accelerator upgraded by 2026 to an order of magnitude higher luminosity. As part of the HL–LHC upgrade project, also other CERN accelerators and their subsystems are receiving upgrades. Among other work, the LINAC 2 linear accelerator injector was decommissioned and replaced by a new injector accelerator, the LINAC4.