Inhaltszusammenfassung

Direct Dark Matter detection is an ongoing and quickly developing eld in astroparticle physics, aiming to measure the scattering of Dark Matter particles with Standard Model particles. With detectors searching for predicted Dark Matter particles and narrowing the parameter space over the last three decades, the technological approach becomes more and more challenging. Today the best limits on Dark Matter mass and cross-section are set by dual-phase xenon time projection chambers (TPC). To inc...Direct Dark Matter detection is an ongoing and quickly developing eld in astroparticle physics, aiming to measure the scattering of Dark Matter particles with Standard Model particles. With detectors searching for predicted Dark Matter particles and narrowing the parameter space over the last three decades, the technological approach becomes more and more challenging. Today the best limits on Dark Matter mass and cross-section are set by dual-phase xenon time projection chambers (TPC). To increase their sensitivity, a deeper understanding of the physical processes in xenon with respect to the energy deposit by impinging particles is crucial. The MainzTPC is a small dual-phase xenon time projection chamber which was co-developed and commissioned in the course of this thesis. Its main goal is to study the scintillation S1 and ionization response of liquid xenon from low-energy electronic and nuclear recoils. Two signals are measured: The primary signal S1 originates from prompt scintillation after the scattering interaction. The secondary signal S2 is the charge signal created in the gas phase. It is proportional to the number of extracted electrons. The MainzTPC also provides a 3D position reconstruction which allows the definition of a fiducialized volume inside the TPC. The charge-to-light ratio for electronic recoils generally is larger than for nuclear recoils which leads to a discrimination method for background events undergoing interactions with the electronic shell of the xenon atoms, such as gamma-rays or electrons. Like neutrons, Dark Matter is expected to scatter on a xenon nucleus. For the low-energy region, this distinction becomes less reliable. The measurement of light and charge yields for liquid xenon for energy deposits down to only a few keV is necessary to improve on this discrimination tool. The experimental part of this dissertation describes the MainzTPC detector as well as its surrounding subsystems which are necessary for operation. The emphasis is set on the data acquisition system, which was developed in the course of this thesis and was used to record the data from Compton scattering as well as neutron scattering. The data presented here are Compton measurements conducted at the nELBE facility at the HZDR. In the analysis part the MainzTPC as a prototype is characterized and examined for its various properties, such as the 3D position reconstruction employing avalanche photodiodes, the determination of the liquid level inside the TPC, signal corrections for S1 and S2 as well as several other parameters (electron drift velocity, electric field strengths in the gas phase, and so on). The light and charge yields of the MainzTPC were measured and show qualitatively similar results as simulations from [1] and previous measurements from [2]. The performance of the MainzTPC is limited by a series of factors, which are described in detail in the analysis part. Examples are a high noise level on the photomultipliers limiting the low-signal detection and the non-feasible TPC calibration data. For future measurements, necessary improvements are discussed.» weiterlesen» einklappen

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DDC Sachgruppe:
Physik