Alterungsstudien und Studium der Betriebseigenschaften des Outer Trackers des LHCb Detektors

The Outer Tracker is part of the LHCb tracking system. It uses drift chamber to measure the track of a particle. The straws have a length of 2.5m and a diameter of 4.9 mm. They are operated in proportional mode and should measure tracks with a precision of 200 μm per hit. In the first part, this thesis presents the results of a performance study for the Outer Tracker, focussing on spatial resolution and efficiency. The main part of this thesis deals with aging studies. Neither a test with 8 keV X-rays nor with highly ionising protons showed any change in the module behavior due to aging. The acceleration factors compared to LHCb were 8-180 (anode current >80 nA/cm) in the most irradiated areas. A charge of up to 3 C/cm was accumulated. Aging tests at anode currents below 15 nA/cm (acceleration factor 1) showed a significant gain drop for the already produced modules after only a few days (1-2 mC/cm) of irradiation. The aging depends on several parameters like gas flow velocity or gas mixture. There is no aging for anode currents >12 nA/cm. This aging is an effect of outgassing material used in the module. Tests showed that the outgassing is probably caused by the epoxy adhesive. Flushing and warming the modules reduce the aging significantly. As things are, the Outer Tracker modules can be operated in LHCb for several years.