The LHC is well known for its hundreds of superconducting magnet assemblies, but it will also use 154 normally conducting “warm” magnets. On 19 February, a celebration took place at CERN to mark the installation of the last of these magnets, which play a key role in shaping the course of the proton beams.
The LHC consists of a number of arcs with straight sections in between, where the magnetic intensity required to bend the beams is not as high as elsewhere, and warm magnets can be used in these places. One advantage is their robustness when exposed to radiation, which is important, for example, in the two long straight sections where collimators clean the beam by removing particles far from the central orbit. Using superconducting magnets here would be problematic, as secondary particles produced in the collimators could reach the magnets and cause a quench. Warm magnets also have the advantage of being more affordable than superconducting magnets and are easier to make and install, owing to their comparative simplicity. Nearly all of the warm magnets were made specially for the LHC and travelled great distances to reach CERN: 48 magnets have come from TRIUMF, Vancouver; 40 from the Institute for High Energy Physics in Protvino, near Moscow; and 65 from the Budker Institute of Nuclear Physics in Novosibirsk, Russia. Only one magnet had a previous existence. Originally built for the ISR in the 1970s, it is now being used in the ALICE experiment.
