On 5 June, the first period of luminosity production at the LHC came to an end and we began our second machine development (MD) session. The MD studies continued until 10 June, when the last MD beams were dumped ahead of the scheduled technical stop. Luminosity production is expected to resume on 17 June for a period of nine weeks of uninterrupted production, until the next MD session, which is scheduled to start on 19 August.

When production beams were dumped on 5 June, the counter for the integrated luminosity showed 30.4 fb^-1 for ATLAS and CMS, 2.5 fb^-1 for LHCb and 17.3 fb^-1 for ALICE, exactly as expected.

During the MD session, many important and very interesting topics were studied, which will benefit both this year’s run and future operations. Notably, the machine optics for the High-Luminosity LHC (HL-LHC) were studied to preempt any issues and ensure that we have enough time to address them.

In the Accelerator Report of 3 May, I discussed the collimator hierarchy problem that emerged on 17 April, when the machine was filled with 1791 bunches per beam. This issue limited the squeeze process, slightly reducing luminosity production. Following numerous studies and a final test last week, the LHC team identified several corrections to be applied to the machine’s settings, which will require it to be revalidated. This will have no impact on physics time, since a short intensity ramp-up is always performed after a technical stop in order to revalidate the accelerator. Once validation is complete, the squeeze process can go back to the values initially planned for this year’s run.

The 2024 run has been extended by four weeks of proton physics, as mentioned in my Accelerator Report of 16 April. The 2024 target for the integrated luminosity has thus been updated from 90 fb^-1 to 110 fb^-1.

With the extra knowledge and experience gained from the MD session, the preventive maintenance performed on the machine and the resolution of the collimator hierarchy issue, we are optimistic that we will have an uninterrupted and successful luminosity production period this summer. We aim to reach an integrated luminosity of 80 fb^-1 for ATLAS and CMS before the next MD session starts, on 19 August, on the way to our new 2024 luminosity target of 110 fb^-1.