The Compact Muon Solenoid silicon tracker: testing of hybrids, modules and substructures at operating temperature

The Compact Muon Solenoid (CMS) is one of two general purpose detectors which are foreseen to operate at the Large Hadron Collider (LHC), which is presently being built at the European laboratory for particle physics (CERN) in Switzerland. The central tracker of CMS consists of a pixel system, which is located close to the interaction point and a silicon strip tracker (SST) which instruments the intermediate and outer region. The SST is composed of 15148 silicon microstrip detector modules which contain the read-out electronics (hybrids) and sensors. These modules will be assembled into substructures with control electronics and optics for transmitting data. The substructures will be integrated into the subsystems of the SST. The SST will be operated for up to ten years in the harsh radiation environment of the LHC. The lifetime of the SST will be extended by operating the detector at lowered temperature. The sensors, which are very delicate parts in respect to radiation damage, will be operated at a maximum temperature of -10 degrees C. Since the assembly of the modules as well as the mounting on substructures is done at room temperature, tests in a CMS-like environment are necessary to prove the mechanical and electrical stability.