Since 4 December, around 500 technicians and engineers have been working flat-out to maintain and upgrade the Large Hadron Collider (LHC) and other parts of the CERN accelerator complex. The current year-end technical stop will last until 9 March, and preparations for the machine and its infrastructure for the High Luminosity LHC (HL-LHC) have been a focus of activities.

Collimators are key to operating the HL-LHC, which will have roughly twice the stored energy (700 MJ) as the present machine. These devices control losses from the circulating proton beams so that they can be constrained to a small section of the machine’s circumference. Continuing work undertaken during last year’s extended year-end stop (CERN Courier March 2017 p9), two new collimators are being installed at point 1 containing a wire that generates an electromagnetic field to compensate for long-range beam–beam effects.

Higher performing injectors that can produce more intense particle beams are another demand of the HL-LHC, and this aspect is being managed by the LHC Injector Upgrade (LIU) project (CERN Courier October 2017 p32). An upgraded kicker magnet, one of eight fast-pulsed magnets that inject particle beams coming from the Super Proton Synchrotron (SPS) into the LHC, will be installed at point 8. A special coating applied to the inner wall of the ceramic pipe of the magnet is one of several techniques developed to reduce the heating of components in the harsher HL-LHC environment.

While work steps up on the LHC, which has been temporarily emptied of its 120 tonnes of helium coolant, brand-new accelerator technology that will help the HL-LHC achieve its unprecedented luminosities is being prepared for tests in the SPS. Two prototype radiofrequency crab cavities – designed to tilt particle bunches before they collide to maximise the overlapping of the beams and increase the probability of collisions – have been installed for testing during 2018. In around five years from now, during Long Shutdown 3 (LS3), the full system will be installed in the LHC.

Further down the accelerator chain, a major de-cabling campaign is taking place in the Proton Synchrotron (PS) to create space for the deployment of the LIU project during Long Shutdown 2 (LS2) beginning next year. The transfer line linking the PS to the SPS is also having all of its 43 quadrupole magnets replaced, among numerous other works. The whole CERN injector chain is undergoing an annual check-up, in particular concerning the cooling, ventilation, cryogenics and electrical supply systems. Other important activities are taking place to consolidate the infrastructure, such as the installation of a new lift at LHC point 8, and to update the beam control systems.

During the 2018 LHC performance workshop, held in Chamonix from 29 January to 2 February, the performance of the LHC during 2017 was reviewed and operational scenarios for 2018 were discussed. A particular focus of the workshop was on the status of the LIU and HL-LHC projects, which will be rolled-out in LS2 and LS3, respectively. There was lively discussion about the organisation and planning of activities for LS2, and the final session of the workshop covered the full energy exploitation of the LHC. Until LS2 the machine will run at a centre-of-mass energy of 13 TeV, but prospects for running at 14 TeV after LS2 and eventuallly even 15 TeV were also discussed.