On 23 October, the CERN Management validated the new schedule for activities taking place during the second long shutdown (LS2), which began at the start of 2019. The schedule has had to be modified due to the COVID-19 pandemic.
The operation of CERN's accelerators is subject to scheduled shutdowns to allow important repair and upgrade work to take place. The present shutdown, LS2, is devoted to preparations for Run 3 of the LHC, which will have an integrated luminosity (indicator proportional to the number of collisions) equal to the two previous runs combined, and for the High-Luminosity LHC (HL-LHC), the successor to the LHC, which will begin operation at the end of 2027.
The new schedule for LS2 anticipates that the first test beams will circulate in the LHC at the end of September 2021, four months later than the date planned before the COVID-19 crisis. To give the LHC's main experiments - ATLAS, CMS, ALICE and LHCb - time to complete their own upgrade programmes, Run 3 of the LHC will begin at the start of March 2022.
"At the end of May, after the first lockdown, activities were able to gradually restart on the CERN sites, albeit with an extra challenge: to carry out the extensive work involved in LS2 while scrupulously respecting the health and safety measures put in place to combat COVID-19," says José Miguel Jiménez, head of CERN's Technology department.
Despite these difficulties, and thanks to the hard work of the LS2 teams, the activities are going well. At present, the LHC is already in its cooldown phase and the first of the accelerator's eight sectors reached its nominal temperature (1.9 K or -271.3 °C) on 15 November. The whole machine should be "cold" by spring 2021. Next come electrical quality tests, powering tests and a long campaign of quench training for the magnets to allow them to reach their nominal magnetic field.
As for the LHC's injectors, they will gradually be started up as of next month. The many experiments at ISOLDE and the PS-SPS complex (except for those using ion beams) will therefore be able to start taking data as of summer 2021.
No changes have been made to the schedule beyond 2022. The third long shutdown (LS3) will begin at the start of 2025 and end in mid-2027. This is when the equipment for the HL-LHC and its experiments will be installed. The HL-LHC will generate 10 times as many collisions as its predecessor! This will allow physicists to study known mechanisms, such as the Brout-Englert-Higgs mechanism, in detail, and to observe possible very rare new phenomena. Accordingly, the upgrades to the LHC experiments will give them considerable potential for discovery.
