Analysis of beam test data by global optimization methods
Successful track reconstruction in a silicon tracking device depends on the quality of the alignment, on the knowledge of the sensor resolution, and on the knowledge of the amount of material traversed by the particles. We describe algorithms for the concurrent estimation of alignment parameters, sensor resolutions and material thickness in the context of a beam test setup. They are based on a global optimization approach and are designed to work both with and without prior information from a reference telescope. We present results from simulated and real beam test data.
Performance studies on the ohmic side of silicon microstrip sensors
High precision collider experiments at high energy accelerators and B-factories need accurate position resolution while preserving a low material budget for precise particle tracking. Thin double-sided silicon detectors (DSSDs) fulfill both requirements, if a careful sensor design is applied to maintain a high charge collection efficiency. In this continuation of a previous study we investigate the p-stop and the p-spray blocking methods for strip isolation on the n-side (ohmic side) of DSSDs with n-type bulk. We compare three different p-stop patterns: the common p-stop pattern, the atoll p-stop pattern and a combination of these patterns, and for every pattern four different geometric layouts are considered. Moreover we investigate the effect of the strip isolation on sensors with one intermediate strip. Sensors featuring these p-stop patterns and the p-spray blocking method were tested in a 120 GeV/c hadron beam at the SPS at CERN, gamma-irradiated to 100 kGy at SCK-CEN (Mol, Belgium), and immediately afterwards tested again at CERN in the same setup as before. The results of these tests are used to optimize the design of DSSDs for the Belle II experiment at KEK (Tsukuba, Japan).
Strahltest und Bestrahlung von Silizium Teilchendetektor-Prototypen
In this diploma thesis the usability of particle detectors for their use in a large particle physics experiment is verified. For this verification they are used during a beamtest at the super proton synchrotron at CERN. First there is a description of the mode of operation and interactions of particles with the detectors, the readout system as well as the experiment and the characeristic damages of silicon particle detectors under irradiation. To analyze the data, software will be extended by fitting modules, calculation modules for signal to noise (SNR) ratio and new reporting modules. Additionally existing components will be modified to be able to analyze the data. Because there has been a speculation about errors accounted for by the fabrication process and because the behaviour of the detectors after irradiation is essential for characterisation of particle detectors, the detectors have been irradiated at an Co60 gamma source. This irradiation was followed by another beamtest. At the end there is an interpretation of the results according to the performance and effects of the irradiation as well as an interpretation according to the suspected manufactoring errors. Results also will be compared to electrical measurements that have been performed parallel to this thesis.
Discrimination of coherent and incoherent cathodoluminescence using temporal photon correlations
We present a method to separate coherent and incoherent contributions of cathodoluminescence (CL) by using a time-resolved coincidence detection scheme. For a proof-of-concept experiment, we generate CL by irradiating an optical multimode fiber with relativistic electrons in a transmission electron microscope. A temporal analysis of the CL reveals a large peak in coincidence counts for small time delays, also known as photon bunching. Additional measurements allow us to attribute the bunching peak to the temporal correlations of coherent CL (Cherenkov radiation) created by individual electrons. Thereby, we show that coincidence measurements can be employed to discriminate coherent from incoherent CL and to quantify their contribution to the detected CL signal. This method provides additional information for the correct interpretation of CL, which is essential for material characterization. Furthermore, it might facilitate the study of coherent electron-matter interaction.
Discrimination of coherent and incoherent cathodoluminescence using temporal photon correlations
We present a method to separate coherent and incoherent contributions of cathodoluminescence (CL) by using a time-resolved coincidence detection scheme. For a proof-of-concept experiment, we generate CL by irradiating an optical multimode fiber with relativistic electrons in a transmission electron microscope. A temporal analysis of the CL reveals a large peak in coincidence counts for small time delays, also known as photon bunching. Additional measurements allow us to attribute the bunching peak to the temporal correlations of coherent CL (Cherenkov radiation) created by individual electrons. Thereby, we show that coincidence measurements can be employed to discriminate coherent from incoherent CL and to quantify their contribution to the detected CL signal. This method provides additional information for the correct interpretation of CL, which is essential for material characterization. Furthermore, it might facilitate the study of coherent electron-matter interaction.
Temporal correlation in coherent cathodoluminescence
Published at the 16th Multinational Congress on Microscopy (16 MCM)
Towards a levitated atom interferometer with potassium
Published at the Terrestrial Very-Long-Baseline Atom Interferometry Workshop at CERN
We develop a setup suitable for cavity-enhanced levitated atom interferometry, which is capable of very long interaction times. By holding atoms in a lattice, short- ranging potentials can be measured, enabling high precision experiments allowing to search for new physics and light induced interactions. The small hyperfine splittings simplify the generation of laser frequencies needed for cooling the bosonic isotopes 39K and 41K from a single laser using acousto-optic modulators. The experiment consists of a transfer chamber separated by a valve to a science chamber, which facilitates the insertion of samples, e.g. test masses to measure their effect on the potassium atoms, but also allows for inserting electron sources to perform experiments to realize coherent interactions between atoms and electrons.
Towards Driving Quantum Systems in Cryogenic Environments with the Near-Field of Modulated Electron Beams
Published at the 13th ASEM (Austrian Society for Electron Microscopy) Workshop
Coherent electro-magnetic control of quantum systems is usually done by electro-magnetic radiation - which limits addressing single selected quantum systems, especially in the microwave range. In our proof of concept experiment we want to couple for the first time the non-radiative electro-magnetic near-field of a spatially modulated electron beam to a quantum system in a coherent way. As the quantum system we use the unpaired electron spins of a free radical organic sample (Koelsch radical - α, γ-Bisdiphenylene-β-phenylallyl) that is excited via the near-field of the modulated electron beam. The readout of the spin excitation resembles a standard continuous wave electron spin resonance experiment and is done inductively via a microcoil using a lock-in amplifier. In the long term this experiment should demonstrate the feasability of coherent driving and probing of quantum systems far below the diffraction limit of electro-magnetic radiation by exploiting the high spatial resolution of an electron beam.
