Setup of a Drift Tube Muon Tracker and Calibration of Muon ...

Figure 3.3: Setup of the muon tracker in the laboratory in Hamburg. The photographshows the four drift tube modules placed on top of each other. Two of the modulesare rotated by 90 ◦ . The HV and preamp boards are placed at the front end of themodules (cf. Section 3.2.4 for details). The read out and control electronics as well asthe power supplies are located in the rack behind the detector. On top and underneaththe detectors, layers of plastic scintillators are placed for triggering. To reduce triggersfrom low energetic cosmic showers, a layer of lead is placed above the lowest scintillator.drift tube hits are needed to find an unambiguous solution.3.2 SetupThe muon tracker is built out of four identical modules formerly used as a prototypeof the OPERA PT [58]. This section describes the layout of these modules as well astheir setup for a 3D reconstruction. A photograph of the setup is shown in Fig. 3.3.3.2.1 Drift Tube ModulesEach module consists of 48 aluminum drift tubes. The tubes are arranged in fourlayers. Each tube has an outer diameter of 38 mm and an inner diameter of 36.3 mm.In the center of each tube, a gold plated tungsten wire of 45ñm diameter is strungserving as an anode. The modules are 1.05 m long (1.10 m including end plates).The end plates have a cross section of 19.4 × 55cm 2 .Each layer of 12 drift tubes within a module is shifted against the neighboringlayer. The staggering has been optimized for a maximum number of hits for tracksperpendicular to the drift tube plane. A cross section of the drift tube modules ispresented in Fig. 3.5. In each layer the tubes are arranged at a distance ∆x = 42 mm.The following layer is shifted by −21 mm in the x-direction, so that the center ofa tube is at a distance of again 42 mm to both neighboring tubes in the first layer.The shift in y is thus given as ∆y = √ 42 2 − 21 2 mm ≃ 36.4mm. The next layeris then shifted by 40.6 mm in the y-direction whereas the x-coordinate is shiftedasymmetrically by 11 mm. The fourth layer is then again shifted symmetrically by24