Optimization of a transition radiation detector for the compressed baryonic matter experiment

The Transition Radiation Detector (TRD) of the compressed baryonic matter (CBM) experiment at FAIR has to provide electron-pion separation as well as charged-particle tracking. Within this work, thin and symmetric Multi-Wire Proportional Chambers (MWPCs) without additional drift region were proposed. the proposed prototypes feature a foil-based entrance window to minimize the material budget and to reduce the absorption probability of the generated TR photon. Based on the conceptual design of thin and symmetric MWPCs without drift region, multiple prototypes were constructed and their performance presented within this thesis. With the constructed prototypes of generations II and III the geometries of the wire and cathode planes were determined to be 4+4 mm and 5+5 mm. Based on the results of a performed test beam campaign in 2011 with this prototypes new prototypes of generation IV were manufactured and tested in a subsequent test beam campaign in 2012. Prototypes of different radiators were developed together with the MWPC prototypes. Along with regular foil radiators, foam-based radiator types made of polyethylene foam were utilized. Also radiators constructed in a sandwich design, which used different fiber materials confined with solid foam sheets, were used. For the prototypes without drift region, simulations of the electrostatic and mechanical properties were performed. The GARFIELD software package was used to simulate the electric field and to determine the resulting drift lines of the generated electrons. The mean gas amplification depending on the utilized gas and the applied anode voltage was simulated and the gas-gain homogeneity was verified. Since the thin foil-based entrance window experiences a deformation due to pressure differences inside and outside the MWPC, the variation on the gas gain depending on the deformation was simulated. The mechanical properties focusing on the stability of the entrance window was determined with a finiteelement method to facilitate an approximation on the gas-gain variation. The properties of the prototypes were verified with in-lab measurements. The simulated expansion of the foil-based entrance window was validated with overpressure tests. The absolute gas gain was measured in a setup using ionizing radiation of a ⁵⁵Fe source. The homogeneity of the relative gas gain of the generation IV prototypes at a given expansion of the entrance window as well as the energy resolution were also determined. The objective of this work was the determination of the electron-pion separation capabilities of the MWPC prototypes combined with different radiator prototypes. In test beam campaigns 2011 and 2012 the prototypes of generation II, III and IV were exposed to a mixed electron-pion beam at the CERN PS. The spectra of total deposited charge for electrons and pions were measured. Based on the generated spectra of deposited charge, the electron-pion separation performance of MWPC prototypes combined with the utilized radiator prototypes were evaluated in this work. The electron-pion separation was also analyzed depending on the momentum of the detected particle. Using the information of the employed cluster-finding algorithm the pad response functions were determined.