The World of International Organizations

CERN particle collider to reopen in 2021

CERN's Large Hadron Collider (AN/John Heilprin)

GENEVA — The world’s biggest atom smasher will restart in September 2021, a half year later than planned, and will operate for an extended run until the end of 2024, the European Organization for Nuclear Research said on Friday.

Managers at the international organization, known by its French acronym CERN, agreed to the new operating calendar with the approval of a governing council of 23 member nations. The council also was responsible for reappointing Fabiola Gianotti, an Italian physicist, to a second five-year term as CERN’s director-general starting in January 2021.

CERN completed a major milestone by connecting several tunnels 100 meters underground between the LHC and its successor, the High-Luminosity LHC. A second connection between the new tunnels and the LHC tunnel also was completed. The underground structures are due to be fully completed by mid-2021, CERN said, while the surface buildings are scheduled to be finished by mid-2022.

The LHC has a limited life-span and is sometimes shut down for repairs or upgrades. Since 2018 the collider has been going through a major upgrade that is referred to as LS2. Its purpose is to increase the number of proton collisions for experiments, which boosts the probability of more discoveries about the universe’s fundamental properties.

The upgrade initially was due to be completed by early 2021 but “the schedule has had to be modified due to the COVID-19 pandemic,” CERN said in a statement.

It is now expected to operate in a high-luminosity mode by the start of 2028. Luminosity refers to the number of collisions among sub-atomic particles. The higher the luminosity, the more data become available. The upgrades will increase the number of proton collisions for experiments.

“At the end of May, after the first lockdown, activities were able to gradually restart on the CERN sites, albeit with an extra challenge: to carry out the extensive work involved in LS2 while scrupulously respecting the health and safety measures put in place to combat COVID-19,” said José Miguel Jiménez, head of CERN’s technology department.

More data, better detectors

The LHC uses more than 50 types of electromagnets to send particles along complex paths without losing speed. Main dipoles generate powerful 8.3 tesla magnetic fields, which are 100,000 times more powerful than Earth’s magnetic field. The electromagnets use a current of 11,080 amperes to produce the field. A superconducting coil allows high currents to flow without losing energy to electrical resistance.

It is now in what CERN refers to as a “cooldown phase,” and the entire machine should be “cold” by spring 2021. Afterwards, scientists will begin doing electrical quality tests, powering tests and quench training for the electromagnets to reach a nominal magnetic field. After the injectors are gradually started up, experiments can start taking data. A third long shutdown and upgrade, termed LS3, is due in 2025.

In 2012, CERN hailed the discovery of a “missing cornerstone of physics” when it detected a new subatomic particle, the Higgs boson, that helps explain why all matter has mass. Its existence was predicted nearly a half-century earlier. But over the past several years CERN has been working on extensive upgrades to its accelerator complex and experiments in preparation for the next run of its LHC.

Major work is being carried out on all the machines and infrastructures, the international organization said, with the particle accelerator chain undergoing thorough renovations and other new equipment being installed where the upgrades continue. But to be able to handle all the extra data that the atom smasher will generate, CERN’s data detectors are being improved, too.

“The High-Luminosity LHC will generate many more collisions than the LHC, accumulating 10 times more data than its predecessor throughout its operation,” CERN said in a statement. “This groundbreaking machine will thus be able to detect extremely rare phenomena and improve the precision of measurements of the infinitesimally small.”

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