On 10 December 2018 at 6.01 a.m., the electronic logbook of the PS read: “Beam stopped!”. Just before that, the last lead ions of Run 2 had circulated in the machine. Protons had already been stopped on 12 November, with the permanent closure of Linac2.
For the PS, Long Shutdown 2 (LS2) had started and the responsibility for the accelerator was handed over from the Operations group (BE department) to the Accelerator Coordination and Engineering (ACE) group (EN department).
The same day, a well-planned and well-orchestrated schedule of activities was set in motion by the ACE team to perform the necessary maintenance and consolidation in the PS, and, more importantly, to start the LHC Injectors Upgrade (LIU) project activities.
Many, if not all, groups in the Accelerators and Technology Sector (ATS), as well as several groups within CERN’s other departments, delivered excellent work, with the timely development and construction of large amounts of new equipment that was installed in and around the PS during the LS2 period.
One year, nine months and thirteen days later, on Friday, 23 October (on schedule, not counting the three months of delay caused by COVID-19), the key of the PS accelerator was handed back to the Operations group.
All the hardware and software will now go through a period of commissioning, before a full cold check-out of the PS. After that, beam commissioning will start, on 1 March 2021 if all goes to plan.
The Operations group, in close collaboration with the equipment and service groups, now has the honour of making the Proton Synchrotron, which is more than 60 years old – although it has been largely refurbished – operational again, with the aim to deliver the first beams in spring 2021.