Academic publications are usually linked to my ORCID 0009-0002-0979-7880
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.
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).
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.
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.
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.
Published at the 16th Multinational Congress on Microscopy (16 MCM)
Presented at the DPG-Frühjahrstagung der Sektion Atome, Moleküle, Quantenoptik und Photonik (SAMOP 2023)
Coherent manipulation of quantum systems generally relies on electromagnetic radiation as produced by lasers or microwave sources. In the experiment presented here we attempt a novel approach to drive quantum systems, as it was recently proposed (D. Rätzel, D. Hartley, O. Schwartz, P. Haslinger, A Quantum Klystron - Controlling Quantum Systems with Modulated Electron Beams. Phys. Rev. Research 3, 023247, 2021). This method utilizes the non-radiating near-field of a modulated electron beam to coherently drive quantum systems, leading to new possibilities for controlling quantum states. For instance, one can locally address subsystems far below the diffraction limit of electromagnetic radiation or paint potentials at atomic scales. In this proof of concept experiment, we want to couple the oscillating near-field of a spatially modulated electron beam to the unpaired spins of a solid, organic radical sample (BDPA) or the hyperfine levels of laser cooled Potassium atoms. The electron beam is generated with a cathodic ray tube from a fast analog oscilloscope.
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.
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.
Presented at the 54th Annual Meeting of the APS Division of Atomic, Molecular and Optical Physics
Coherent manipulation of quantum systems with precisely controlled electromagnetic fields is one of the key elements of quantum optics and quantum technologies. Here, I will give an overview of our recent work, which theoretically demonstrates that the non-radiative electromagnetic near-field of a temporally modulated free-space electron beam can be utilized for coherent control (even on the nanoscale e.g. in an electron microscope) of quantum systems. I show that such manipulation can be performed with only classical control over the electron beam itself and that potential challenges like shot noise and decoherence through back action on the electrons are for certain parameter ranges insignificant for our approach. I will present possible experimental realizations using laser cooled, state-selected potassium atoms or unpaired electron spins in a solid state sample such as BDPA and point out interesting applications for example painted potentials, which could be realized using a spatially modulated electron beam.
Presented at the seminar at Atominstitut der Technischen Universität Wien
Electron spin resonance is a widely used analytical tool in medicine, biology and material sciences. Spin systems have many applications in quantum physics - for example in quantum computing and sensing. Traditionally such spin systems are driven with microwaves which offer only limited spatial resolution. We are currently in the process of developing and building experiments with the aim to coherently drive electron spin systems with high spatial resolution using the collective effect of the non radiative near field of modulated electron beams. Since electron microscopes offer a well established and highly capable platform for electron beam experiments we want to integrate our experimental setup in a scanning electron microscope. This also opens up future possibilities to perform in-situ electron spin analysis in scanning electron microscopes. In this talk I'm going to give a quick introduction to electron spin resonance and it's applications, our approach and our existing experimental setups as well as our current efforts and characterization measurements that have been performed to introduce this novel approach to interact with spin systems into an scanning electron
Presented at the 14th ASEM (Austrian Society for Electron Microscopy) workshop
In recent years, fast electron microscopy has garnered increased interest within the scientific community. Particularly, temporal correlation measurements have proven to dramatically enhance the useful signal by suppressing background noise. Here, we introduce a new method of imaging at the intersection of quantum optics and electron microscopy. Ghost imaging, also known as coincidence imaging, of an object is a method in classical and quantum physics that involves constructing an image by gathering information from past correlation measurements. We perform coincidence measurements using electron-photon pairs which are correlated in momentum and position. To produce correlated electron-photon pairs we use a transmission electron microscope (TEM) working at an acceleration voltage of 200 keV to illuminate a thin monocrystalline silicon membrane of 100 nm thickness. Primary electrons scatter inelastically inside the membrane and undergo a small momentum deflection, simultaneously emitting coherent photon emission through a process known as cathodoluminescence (CL). As a result, the emitted photons are correlated in momentum and position with the transmitted electrons. We guide correlated photons through an object, which we are interested in imaging, and detect electrons directly with a pixelated camera. Despite electrons never directly interacting with the object, we are able to perform ghost imaging of the object through correlated electron-photon pairs.
Presented at the 14th ASEM (Austrian Society for Electron Microscopy) workshop
Electron spin resonance is a widely used analytical tool in medicine, biology and material sciences. Traditionally, electron spin systems are driven by microwaves, which offers only limited spatial resolution due to the long wavelength of microwaves, which can be optimized by sophisticated techniques such as the use of magnetic field gradients. We propose a different way of driving spin systems using the non-radiative near-field of a modulated electron beam in a scanning electron microscope by tuning the microscopes to higher beam currents and using additional beam modulation mechanisms. Driving systems with higher harmonics of the modulated beam opens up future possibilities to perform in-situ electron spin resonance analysis with high spatial resolution down to the nanoscale. To perform our experiments we modified an Philips XL30 ESEM to allow for high frequency beam modulation, cryogenic cooling of our samples and microwave frequency readout of our spin systems.
Dipl.-Ing. Thomas Spielauer, Wien (webcomplains389t48957@tspi.at)
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