LHC Magnet Repair Has Begun

by Anais Schaeffer, CERN Contributor, anai.schaeffer@cern.ch

Major work is underway on the CERN Large Hadron Collider (LHC) with the extraction of magnets from the accelerator tunnel. The LHC has a total of 1232 dipoles, magnets which bend the particles’ trajectories, and 474 quadrupoles, which squeeze the bunches. All these magnets are superconducting, i.e. they operate at a temperature of -271 °C, are 15 meters long and weigh up to 28 tons. So moving them around is no trivial matter.

During the second long shutdown, 22 of these large components (including 19 dipoles) have to be replaced, especially as several have been showing operating deficiencies.

The replacement magnets are arriving one-by-one. Ten new magnets have been installed, aligned and are being connected in the first sectors of the accelerator (sectors 8-1 and 1-2). This involves reconnecting the beam-pipes, the superconducting cables that transport currents of up to 13,000 amps, the transfer lines for the helium that cools the magnets and the beam shields that thermally insulate the magnets once they have been cooled down to -271 °C. Care needs to be taken to ensure the tightness of the insulating vacuum, and tests are then carried to check that the new magnets are perfectly interconnected with the neighboring magnets. These operations take several weeks for each magnet. All 22 magnets should thus be connected at the beginning of 2020.