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LHC Report: A busy end of the proton run

The final days of the LHC proton physics Run II are here



The LHC schedule following the approval of the special physics run and the addition of the 4 extra Machine Development (MD) days. The two special physics days in week 42 have become luminosity production days.

The last LHC Report mentioned that the schedule contained a seven-day special run block placeholder in week 41 for the low-energy and high-beta run and that a final decision on the subject would be made following a test run on Tuesday, 2 October.

The results of this test were analysed by the ATLAS-ALFA and TOTEM experiments and, after discussion with the machine teams on the run strategy, it was ultimately decided to perform the run, but to shift its start to Thursday, 11 October and limit its duration to six days, which means we will have another week of luminosity production before ending the proton run on 23 October.

The set-up of the required machine conditions was very efficient and the machine availability during this special run was higher than anticipated. As a result, the special physics run was completed earlier than expected on Sunday night, with over a million events per experiment, allowing the luminosity production to resume two days earlier than scheduled. Unfortunately, during the weekend, a filter in the cryogenics system at Point 8 started to clog, reducing the cooling capacity to less than that required for the high luminosity production. Consequently, it was decided on Monday morning to dedicate some time to solving the issue. Therefore, beam operation was not resumed until early on Tuesday morning, leaving one extra day for luminosity production nevertheless.

During the LHC Performance workshop that was held in Chamonix last January, a promise was made that if the luminosity production made it possible to reach the goal of 60 fb-1 for both ATLAS and CMS, extra machine development (MD) days would be allocated towards the end of the run in order to cope with the long list of topics to be studied before LS2.

The values for the integrated luminosity in 2018. Left for ATLAS and CMS, middle for LHCb and right for ALICE.

Last week, just before starting the special physics run, this goal was reached and, as a result, four extra MD days were added to the final schedule, bringing the total number of days for the MD4 block to seven. This gave the MD coordination team an additional task, as well as the injectors team, who, besides making the final adjustments for the production of the lead ion beam, now also have to prepare and adjust the additional beam configurations required for the LHC MDs. This increases the workload during what is already a busy period, when everybody wants to take advantage of the last protons before LS2.