In the early hours of 13 June, the first of the two gigantic toroid magnet endcaps touched the ATLAS cavern floor. The second endcap followed suit on 12 July. With this delicate operation complete, the ATLAS collaboration has now finished lowering all of the large heavy pieces of detector into the cavern.
The last steps were not without challenges, particularly for the first endcap. These included removing a 5 m portion between the top of the main door and the roof to fit the 13 m high, 240 tonne endcap into the building. Once inside, it was lifted by a mobile crane and secured to two gantry cranes on either side of the entry shaft.
Another issue was that the endcaps were higher than the 2 × 140 tonne overhead travelling crane used to lower them down to the cavern floor. In order to secure an endcap to this crane, it first had to be suspended by the two gantry cranes and lowered 5 m to the correct height using a system of jacks. At the end of the 80 m journey down the shaft, each endcap was placed between the barrel part of the detector and the wheels of the endcap muon chambers with a precision of 2 mm and a margin of 10 cm on either side.
The LHCb collaboration has meanwhile completely installed, interconnected, pumped down and baked out all four sections of the LHCb beam pipe, which includes a section that connects to the vacuum vessel containing the VErtex LOcator (VELO). The largest of the four conical sections is composed of stainless steel and the others are made of beryllium to minimize background in the experiment. One of the more challenging tasks was the installation of the longest section of beryllium beam pipe (6 m) through the RICH2 detector in January, which used temporary rails to guide it through the inner tube with a leeway of only 4 cm. In February, a crane was used to lift the 160 kg stainless steel section and position it in the middle of the iron walls of the muon system on supports that align it with the beamline.
After all of the installation work, the next step was to pump the beam pipe down to a pressure of 10–7 mbar. During the following bake out and non-evaporable getter (NEG) activation, the VELO was heated to 150 °C and the NEG reached 220 °C to obtain an ultra-high vacuum inside the beam pipe. Once the bake-out was complete, the pressure had gone down to 10–11 mbar.
