After a two-year upgrade to nearly double the power of the machine, LHC is ready to restart.
The first running of the machine confirmed the existence of Quark Gluon plasma and gave a wealth of scientific results, but scientists stress they still need to understand the properties of this new form of matter and the role of strong interaction in building ordinary matter.
There’s been a huge amount of work done on the LHC over the past two years – for example, every single one of the electrical links between the thousand magnets in the accelerator ring has been reworked. This means that it will be able to operate at almost double the previous beam energy, bringing huge potential for new discoveries beyond the Higgs boson that was found in 2012. But it also means that the machine that’s now being started up is almost a new LHC, and it’s not a trivial challenge. Nonetheless, everything is on track for the LHC experiments to start collecting data in this new era by May 2015.
Beams came knocking at the LHC’s door for the first time on 22–23 November, when protons from the Super Proton Synchrotron passed into the two LHC injection lines and were stopped by beam dumps just short of entering the accelerator. The LHC operations team used these tests to check the control systems, beam instrumentation and transfer-line alignment. Secondary particles – primarily muons – generated during the dump were in turn used to calibrate the two LHC experiments located close to the transfer lines: ALICE and LHCb.
The next milestone in the preparation for the LHC startup is the sector tests, scheduled for the beginning of March. Proton beams from the SPS will be injected into the LHC from both injection points: beam 1 will go through ALICE and will be dumped on the collimators in Point 3 of LHC and beam 2 will go through LHCb up to Point 6 of LHC, the LHC beam dump.
ALICE is ready to exploit these injection tests at best: in fact, they will be used to check the timing of the signals produced by the trigger detectors (as the ALICE trigger system was also updated during the shutdown); also for the alignment of the muon spectrometer. Finally the injection tests are needed to calibrate the ALICE Beam Condition Monitoring system (consisting of diamond detectors and scintillators) which is critical to protect the experiment during the upcoming beam operation.
With the LHC RUN2 approaching fast, ALICE collaborators have started taking shifts to bring the detector out of the commissioning phase.
The operations are performed in the newly renovated and enlarged ALICE RunControl Centre (ARC). The ARC fits the three main operators, the Run Coordination team, and accommodates all the detector experts of the 20 sub-systems which compose the ALICE detector. The shift crews are present in the ARC 24/7 to perform commissioning (the so called technical runs), physics data taking using cosmic rays and to respond to the LHC “dry runs” (where the accelerator interface with experiment is tested).
In the next issues of ALICE Matters we will introduce some of them along with the new faces who enter the ARC for the first time.