Performance studies on stacked silicon strip sensors

Autoren: Erik Huemer
Kategorie: Masters-Thesis

Today's high energy physics experiments already utilise very sophisticated detector technologies that enable precise reconstruction of the structure and kinematics of particle collision thus allowing to draw conclusions about the constitution of matter. Demands on detector systems, concerning precision, speed and material budget, are increasing as new colliding beam experiments like ILC (International Linear Collider) or upgrades to current ones like LHC (Large Hadron Collider) arise. Beginning with a short description of the LHC and the CMS (Compact Muon Solenoid) concept followed by a preview of the plans for an upgrade, this diploma thesis will also give an overview of the functionality of silicon strip detectors and some insight in the testing of sensors at CERN with the main topics being the analysis of stacked silicon strip sensors for incident angle resolution and the development of software for the processing of raw sensor data. To gain information on the momentum of charged particles after their production in the central interaction point, a detector module with two stacked strip sensors was designed at the Institute of High Energy Physics which allows the estimation of transversal momentums through the measurement of incident angles. This information is mandatory for the timely selection of interesting events in the so-called first level trigger system (L1-Trigger). Such track-trigger modules will be an important component of a future CMS upgrade. The concept intends to use the displacement of the track after some millimetres to infer the particles incidence angle, which is directly related to the particles transverse momentum. A restriction on small displacements therefore directly leads to a rejection of particles with a small transverse momentum. Since the strip displacement can be determined on module level this method doesn't require communication between modules. Currently, the second level of the trigger system, the so-called High Level Trigger (HLT) uses the full information of the tracking system to reconstruct tracks. This cannot be achieved in the small time frame available for the L1 trigger while the above described method is potentially quick enough. A prototype module was tested with 120 GeV pions at the SPS beam line at CERN. The data analysis aimed to quantify the functionality of the module, geometry and readout logic. Because of the more complex design of this module, parts of the existent analysis procedures were not feasible any more. Therefore a new software was developed which is able to deal with various geometries and readout logics utilising modern programming paradigms and improved data types which furthermore eases extensions and flexibility. The correctness of the basic software algorithms was tested against a well established software framework using standard strip modules.