Work has begun to disconnect the focusing magnets on either side of the ATLAS and CMS experiments, a key step on the road to the HiLumi LHC
Written by:
Anaïs Schaeffer
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The 27 km circumference of the Large Hadron Collider (LHC) contains thousands of magnets of different types – dipoles, quadrupoles, sextupoles, octupoles, decapoles, etc. – which each play a very specific role. Among them are the inner triplets: sets of three quadrupoles (hence the name) located on either side of the four main LHC experiments and used to tightly focus the beams before they collide inside the detectors. The beams must be “compressed” as much as possible in order to increase the probability of particles colliding. These magnets are therefore essential for increasing the luminosity of the LHC, i.e. the number of collisions that occur in a given period of time. The higher the luminosity, the more data the experiments can gather.
This is where the future High-Luminosity LHC (HiLumi LHC) and the replacement of the current inner triplets come in. This major operation is part of the third long shutdown (LS3), and the first magnet interconnection was cut this week. Today, CERN Director-General Mark Thomson visited LHC Point 1 (the ATLAS experiment) to mark the start of the operation.
“The replacement of these magnets with the new HiLumi LHC inner triplets is crucial for the coming high-luminosity years.The first quadrupole of the new triplets should arrive in the tunnel at the start of 2029.In total, 16 cryostats and 28 cryo-assemblies will be installed – a major undertaking,” explains Jean-Philippe Tock, Head of the LS3 Coordination Team.
The new inner triplets are the result of many years of research and development and represent a major step forward compared to the niobium-titanium magnets currently installed in the LHC. Their niobium-tin superconducting coils allow them to produce magnetic fields of 11.3 tesla, about 40% stronger than those generated by the current magnets. They will be installed around the ATLAS and CMS experiments. ALICE and LHCb, which have different physics programmes and modes of operation, do not require the same increase in instantaneous luminosity and will therefore be able to keep their current inner triplets, although these will be improved to allow both experiments to benefit from the luminosity increase.
Since 7 September, teams have been dismantling the sections of the machine on either side of ATLAS and CMS in order to remove the 28 superconducting magnets (including the inner triplets) that need to be replaced.
“Today’s event is a major milestone for CERN, especially for the HiLumi LHC project team.The current inner triplets date back to the LHC construction phase and were installed in the machine between 2005 and 2007.After nearly twenty years of operation, they will give way to a new generation of even more powerful magnets.It’s truly remarkable to witness such a handover from one generation of innovation to the next,” says Markus Zerlauth, the HiLumi LHC Project Leader.