The LHC schedule of the last few weeks has been very busy between machine development, a technical stop and van der Meer scans.
The Van der Meer scan is aimed at calibrating precisely the luminosity measurements provided by each experiment.
This last month has been an intense period for both the LHC and the experiments’ experts.
On June 12, a week of machine development started, during which teams of accelerator physicists and engineers could perform beam studies and equipment tests. These are crucial to guarantee beam stability and optimization not only for the current Run2, but also for the Run3, which will take place after the Long Shutdown 2 (2019-2020), and even in vision of the future HL-LHC project. During this period, the ALICE detector was switched on but ran in very safe conditions.
Then, four days of technical stop followed, which allowed various interventions to be carried out underground. In particular, some power supplies were replaced by newer versions, which are expected to improve the run stability and efficiency.
When the LHC was put to work again, a few days were dedicated to the Van der Meer scan for each experiment, which is aimed at calibrating precisely the luminosity measurements provided by the experiments. The tight schedule of these tests, complicated by some issues that occurred, required an organizational effort and late hour work.
Once the Van der Meer scans were concluded, a special run with a β* of 90 m took place. This unusual working conditions allow TOTEM and CMS, as well as ATLAS and ALFA, to perform special physics. During this run, there were no collisions in ALICE, thus the detector was kept working but no data were taken.
Currently, the LHC is running with nominal 2556 bunch beams and is delivering collisions to all of the four experiments. ALICE is now taking data with normal trigger conditions and will follow this way until the next machine development period, which is planned for the last week of July.