Work to renovate CERN’s oldest accelerator continues as part of the LHC Injectors Upgrade (LIU) project

On 24 November 1959, the Proton Synchotron (PS) accelerated its first beams, making it the most powerful accelerator in the world at the time. Who would have thought that 60 years later, this machine would still be one of the main cogs in the CERN accelerator complex? Incredibly, the PS is still in service. It will even be made more efficient with a bit of tender loving care during this second long shutdown. The LHC Injectors Upgrade (LIU) project includes a long list of work to be carried out on the accelerator and its entire infrastructure.

With the first link in the chain of accelerators being replaced by Linac 4, protons will be injected into the PS Booster at 160 MeV, and then accelerated to 2 GeV (up from 1.4 GeV previously) before being sent to the PS. This is why the PS proton injection line, which is about 20 metres in length, will be entirely replaced. To date, the quadrupole magnets have been installed together with a septum magnet. The equipment will continue to be installed in 2020. The power converters which power the injection line, as well as other LIU equipment, have been replaced and installed in renovated buildings. The cabling is now underway.

In the 628-metre-long accelerator, half of the main magnets are being renovated. This major project, which entails lengthy handling operations, will soon be finished. “48 of the 100 magnets have been removed and a vast majority have already been reinstalled”, explains Fernando Pedrosa. New equipment such as beam wire scanners and internal beam dumps will also be installed in the ring. The teams have used the upgrade works as an opportunity to give the accelerator a deep clean, including the cleaning of certain galleries. The cleaning work, as well as the ongoing Linac 4 tests, require part of the PS to be closed making the work more complex to coordinate. Downstream, the extraction line towards the East Area has been entirely dismantled ahead of the new installation in 2020, as part of the East Experiment Area renovation project.

In addition to the beam lines, the entire infrastructure is also being renovated. The lighting system has been changed, for example, and major work is being carried out on the cooling system. High luminosity requires more intense beams which entails several changes including increased power for the circuits’ cooling plants. “We have reorganized the entire cooling system to double the flow while also reducing running costs”, explains Serge Delaval, Section Leader for Injectors within the Cooling and Ventilation Group. The two plants that use short cooling towers will therefore be replaced with one central plant, which uses a single cooling tower composed of four units. Two of these units were no longer in use and have been fully upgraded.

At the same time, all the pumps and heat exchangers have been replaced, together with three kilometres of pipes! “We have used this consolidation as an opportunity to reduce the environmental impact, particularly regarding the products used to prevent Legionnaire’s disease”, says Serge Delaval. Stainless steel has therefore been chosen over steel as it requires much less anti-corrosion treatment. Similarly, demineralised water will also be used for some circuits.

Work on the cooling system will continue until March and the accelerator upgrade is slated to be finished at the start of next summer.