ALICE concluded its first full year of proton and heavy ion data taking at 18:00 on Monday 6 December when the Large Hadron Collider (LHC) stopped its spectacular 2010 operation.
The harvest of over 1 billion recorded proton-proton collisions, and ninety million recorded heavy ion collisions - amounting to almost 2 Petabytes of data: the equivalent of 1.4 million CDs worth of information - has led to many publications; including five papers on heavy ion physics already.
While data analysis will continue uninterrupted, the ALICE detector has been put to sleep, the shifters are taking a well deserved rest and the control room is deserted. The LHC Christmas break will last until 18 February next year, giving us 11 weeks to prepare ALICE for next year’s run.
Maximilien Brice/CERNThe installation of an EMCAL module into ALICE, during the first upgrade
The two major works taking place during the shutdown period are the installation of six Calorimeter (EMCAL) supermodules, and three Transition Radiation Detector (TRD) supermodules. These elements are already sitting in the SXL2 surface building at Point 2, where they will undergo final tests before being moved down to the cavern.
Even though the leftover bottles from the end-of-run party were still adorning the SX2 hall on the morning 7 December - and with ALICE still in the process of cooling down - the shutdown activities were already going at full steam.
To bring the new modules into the L3 magnet, the shielding of the cavern shaft and the walls around the miniframe must first be removed to allow the opening of the L3 magnet’s doors. The shielding in the shaft - which weighs around 500 tons - and the shielding in the cavern - at about 1100 tons - are both constructed from over 150 individual concrete elements, each weighing between 2.5 and 35 tons. The logistics of this operation had been carefully prepared, and after 8 days - a record time - the magnet was opened.
The last two weeks of this year are reserved for the TRD installation. As the 3 modules are inserted into the spaceframe - the support structure that holds the central ALICE detectors, including the beampipe - this installation operation has to be closely watched by our survey team to make sure that movements and deformations stay within tolerances of less than 1-2 mm. With most of the ALICE subdetectors in place, the installation of new modules around densely packed detector elements and services poses a considerable challenge.
The first two weeks of January will see the calorimeter installation. Since each of the 6 modules weighs 8 tons, the installation is again dominated by heavy handling operations. Safety of personnel and detectors during this operation is of course the top priority. The closure of the experiment is then planned for the last two weeks of January, such that the recommissioning of ALICE can start in early February.
The installation operations are clearly the ‘heaviest’ shutdown jobs, but certainly not the only ones: in addition to all the activities to improve the individual subdetectors, the DAQ, HLT and DCS online systems, and the safety systems, will undergo major upgrades to prepare for 2011. Maintenance of gas systems, detector cooling plants and ventilation units are also on the plan. Last but not least, all evacuation and alarm systems will undergo detailed tests.
Many people will spend the Christmas break in the underground areas, but the successful 2010 operation, and the prospect of an even more exciting physics program for next year are certainly highly motivating and definitely worth the price!