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Accelerator Report: Recommissioning on track as the first beams progress through the complex

The recommissioning of the accelerators is progressing according to schedule. Unsurprisingly, some issues have arisen, but they have been swiftly addressed by equipment experts. First physics in the PS East Area and n_TOF is scheduled to start next week

13 March, 2025

By Rende Steerenberg

In my previous report, I wrote that the first beam injection of 2025 into the PS Booster (PSB) was scheduled for 27 February. However, injection ultimately took place ahead of schedule, at around 11.30 a.m. on 26 February.

Following this, the standalone beam commissioning period for the PSB began. During this phase, the PSB team focused on commissioning the beam within the PSB, without needing to deliver it to downstream machines or experiment areas. This phase concluded with the first beam delivery to the PS at noon on 4 March, also one day ahead of schedule. With this, the PSB standalone commissioning ended, and PS standalone commissioning began.

It is important to note that the conclusion of PSB standalone commissioning does not mean that all its operational beams have been fully recommissioned. The commissioning of the various beam types required by the downstream machines and experiment areas will continue in parallel. These beams will be transferred into the PS at a later stage for further commissioning.

The standalone commissioning of the PS is set to conclude on 14 March, when the SPS is scheduled to receive its first beam of 2025.

Meanwhile, the SPS hardware commissioning has been progressing well, with magnets around the machine undergoing testing by pulsing them to high magnetic fields. On 10 March, while pulsing the magnets, SPS operators detected abnormal vacuum behaviour in sextant 6 of the machine. Under normal conditions, the vacuum pressure in the SPS chamber is around 1 × 10⁻⁸ mbar. However, when the magnets in sextant 6 were pulsed, the pressure increased tenfold, suggesting a small leak in the vacuum chamber that seems to open when the magnets are pulsing to high magnetic fields.

In the coming days, further diagnostics and leak testing will be carried out to pinpoint the exact location of the leak. Similar situations have occurred in the past and were typically resolved by replacing the affected magnet and its vacuum chamber with a spare unit. This exchange, including vacuum pumping after installation, usually takes about 24 hours and is not expected to impact the scheduled delivery of beam for physics to the SPS North Area on 14 April.

home.cern,Accelerators — The signals of two vacuum pressure sensors in sextant 6 of the SPS. On the left-hand side, the normal vacuum pressure is visible and rather flat. Just before 5.00 p.m. on 10 March, the magnets were pulsed and the pressure increased. When the pulsing of the magnets is interrupted, the vacuum pressure recovers somewhat. (Image: CERN)

The year-end technical stop (YETS) activities in the LHC tunnel are also nearing completion, and the machine should be “handed over” from the Engineering department to the Operations group on 13 March. Following this, hardware recommissioning and testing will take place in preparation for the first beam injection, which is planned for 4 April.