With the year-end technical stop (YETS) gradually coming to its end, there are a few more things left to be done in ALICE before the LHC starts running again.
Towards the end of last year and before the start of the YETS the System Run Coordinators (SRC) of each detector submitted a programme and a detailed schedule with all the repairs and interventions that needed to be performed during the YETS to the Technical Board (TB). All these activities are coordinated by the TB while assisting in carrying out these tasks in every possible way.
According to the present LHC schedule, the cavern will be closed on 16 March, thereby ending all technical interventions in ALICE. Recently the detector control system (DCS) software was updated. Therefore the first important step of the commissioning is for every detector to implement and integrate these changes. After these, the detectors will participate in global runs, such as technical, to perform important tests of the upgrade of the data acquisition system (DAQ), as well as cosmic runs, which will be carried out at the beginning of March.
During the cosmic runs data are measured from the interactions of cosmic rays passing through ALICE. “There is a minimum detector configuration required for sensible cosmic tests and data taking. Either the inner tracking system (ITS) plus the time projection chamber (TPC), or ALICE cosmic ray detector (ACORDE) plus TPC have to be ready in order to start taking data from cosmic rays. In the absence of a magnetic field, cosmic rays are very useful for the alignment of the different detectors. Once all detector tests are completed, we can also do some physics with cosmic rays. The more detectors participate, the better” – explains Siegfried Förtsch, ALICE run coordinator. As soon as the magnets can be switched on, they will be set to negative polarity, since a lot of cosmic-ray data were collected with positive polarity during Run 2 of last year.
Another important aspect of the preparation is setting up the shifts for the year. “During the commissioning phase we have decided to fill only two shifts – in the morning and in the afternoon, for both the DCS and data acquisition system (DAQ). At least one of these must be SLIMOS – shift leader in matters of safety, since there are still people in the cavern and some detectors are already running. When we start running with cosmic rays, we will need 24-hour supervision, therefore we will add the night shift as well” – says Siegfried.
Once the cavern is closed and the LHC starts its own commissioning with a beam, the run manager (RM), the shift leader (SL) and the data quality monitoring (DQM) shifter will join the crew. So far about 90 percent of the central shifts have been booked: “We have blocked the shift booking for the proton-lead run, because our experience has shown us that we need expert shifters for that period. In preparation of the proton-lead campaign we will give preference to those shifters that have proven themselves throughout the year.”