| Thema und Kurzbeschreibung | Kommentar |
|---|---|
| Calibration of a GERDA prototype detector in the UZH GERDA test facility GERDA is an experiment to look for the double beta decay in enriched 76Ge detectors immersed in liquid argon, which serves both as a shield and as the detector cooling medium. It is currently under construction at LNGS in Italy and will start taking science data in fall 2009. In our laboratory at UZH we are operating a small LAr cryostat to test prototype, segmented and broad-energy HPGe detectors for GERDA Phase-II. These will be calibrated with standard gamma sources to determine their energy resolution, as well as the discrimination of multiple- versus single-site events (since the expected bb-decays can be characterized as single-site events). Before operating GERDA prototypes, we are testing our liquid argon setup with a small, non-enriched and non-segmented HPGe detector. This work will involve the full characterization of a HPGe detector, including Monte Carlo simulations of the expected signal and comparison with actual data. |
offen BetreuerIn: Michael Tarka |
| Monte Carlo simulations of GERDA calibration sources and comparison with real data The GERDA enriched 76Ge detectors will be calibrated with custom-made, low-neutron 228Th gamma sources. The different calibration source positions will be simulated based on the Geant4 Monte Carlo simulation code (the geometry already exists), and the results will be compared to data taken at the Gran Sasso Laboratory. The goal will be to determine the energy scale and resolution, their stability in time (with weekly calibration runs) as well as the efficiency of a pulse shape analysis method used to distinguish between single and multiple hits in Phase-I detectors. |
offen BetreuerIn: Francis Froborg |
| Monte Carlo simulations of an active LAr shield for GERDA Phase-II In GERDA Phase-I, the ~100 tons of liquid argon surrounding the HPGe crustals are used as a cooling medium for the detectors, and as a passive shield against the natural radioactivity coming from the cryostat and the surroundings. For Phase II, it is planned to instrument the liquid argon with photomultipliers and detect UV light emitted when particles interact in the argon volume. In this work, the effect of such an active argon shield on the overal background in the GERDA HPGe detector array, as a function of the energy threshold in the argon, will be determined by using Monte Carlo simulations based on Geant4. |
offen BetreuerIn: Roberto Santorelli |
| Thema und Kurzbeschreibung | Kommentar |
|---|---|
| Electric field and light collection simulations of a liquid xenon time projection chamber A small (3 kg) liquid xenon time projection chamber (TPC) has been designed and built at UZH. It is used to study the response of liquid xenon to low-energy particle interactions, applicable to dark matter searches. In liquid xenon, such particles produce VUV scintillation photons and free electrons. The former are detected with photomultiplier tubes, while the latter are drifted with an applied electric field and collected on an electrode. It is thus important to understand (1) the efficiency of the chamber for collecting photons, (2) the geometry of the applied electric field, and (3) the expected trajectories of drifting electrons in response to such fields. The project will entail using various simulation packages, including Geant4 and COMSOL. The student will also be involved in the operation of the actual TPC and of the electronics, and will compare simulation results to actual data taken with various calibration sources. |
offen BetreuerIn: Teresa Marrodan Undagoitia |
| Characterization of two QUPID sensors QUPIDs (QUartz Photon Intensifying Detectors) are an interesting alternative to classical PMTs for reading out the UV light signal in a xenon TPC. These devices are made of an avalanche photo-diode (APD) and a photocathode deposited on a quartz window. The electrons, which are created by UV photons hitting the photocathode, are accelerated towards the APD in a focussing electrical field, the voltage difference between cathode and APD being 6 kV. In this work, two QUPID sensors will be characterized: first, at room-temeprature, in a black-box equiped with LEDs and second, in a small LXe-TPC, in order to test their characteristics at liquid xenon temperatures and pressures. |
offen BetreuerIn: Annika Behrens |
| Material screening with a high-purity Ge (HPGe) spectrometer at the Gran Sasso Laboratory (LNGS) Samples from the XENON100 and for the future XENON1t experiments will be screened in the low-background facility operated by our group at LNGS in Italy. To determine the amount of activity from the 238-U, 228-Th chains, as well as from 60-Co, 137-Cs and 40-K, the efficiency of the detector-sample setup is evaluated in a Monte Carlo simulation based on Geant4 (the geometry of the HPGe detector and its shield already exists). Folding in the efficiencies for the various gamma peaks to the acquired spectral data from the samples will allow, after subtraction of the measured intrinsic background, a precise determination of radio-activity of the sample. |
offen BetreuerIn: Ali Askin |
| Analysis of the gamma and alpha backgrounds of the XENON100 dark matter search experiment from the liquid xenon by a time-correlation analysis In order to accurately predict the background of electromagnetic origin in the signal region (given by nuclear-recoils as expected for dark matter particles) of the XENON100 experiment, an understanding of the background intrinsic to the liquid xenon is crucial. It can be determined in situ by a time-correlation study of decays from the 238-U, 232-Th chains and from 85-Kr. |
offen BetreuerIn: Alexander Kish |
| Light calibration and calibration data analysis of the XENON100 detector The XENON100 detector is equipped with 242 photomultiplier tubes (PMTs) to detect the tiny light signal produced by interactions in liquid xenon. The detector's calibration is the first step in the data analysis, thus a precise light calibration of the PMTs is crucial. An optical system based on optic fibers and LEDs has been realized in order to measure all the parameters necessary to characterize the PMTs performance and to monitor their stability during the dark matter data taking. This project will allow both hardware work on the optimization of the calibration procedure (developing new procedures for some PMTs if necessary) and software work to analyze the calibration data (with ROOT) and to write the results to an existing (MySQL) database for the XENON analysis software. |
offen BetreuerIn: Alfredo Ferella |
| Monte Carlo simulation of the light propagation and light pattern analysis
through Neural Network techniques in XENON100 The MonteCarlo (MC) simulation of the light propagation in XENON100 is important for a good understanding of the detector performance and for extracting physical quantities from the data. The first step is the development/optimization of the XENON100 GEANT4 code and the tuning of the MC parameters through comparison of MC results with acquired data. Once the MC simulation has been optimized, several software algorithms can be developed to infer the physical parameters to be used in the dark matter data analysis. This project foresees the development of different algorithms based on Neural Network techniques in order to determine event position reconstruction and to perform a light pattern analysis of the data from the dark matter search run. |
offen BetreuerIn: Roberto Santorelli |
| Thema und Kurzbeschreibung | Kommentar |
|---|---|
| Analysis of R125-R128 data from the Germanium and Silicon Detectors The CDMS Experiment operates 30 Ge and Si detectors maintained below 50 mK at the Soudan Lab in Northern Minnesota. It currently set the world's most stringent limits on spin-independent WIMP-nucleon cross sections for WIMP masses above MZ/2. While results from the Runs 123 and 124 have recently been published, the data from Runs 125-128 is currently being analyzed. The Ba/Ma thesis work would involve the development, testing and efficiency estimation of various physics cuts, based on gamma- and neutron calibration data. |
offen BetreuerIn: Tobias Bruch |
| Analysis of the CDMS data for dark matter particle candidates and solar axions The CDMS Experiment operates 30 Ge and Si detectors maintained below 50 mK at the Soudan Lab in Northern Minnesota. The data from Runs 125-128 is currently under analysis. In this analysis the sensitivity of CDMS to neutralinos (the lightest SUSY particle), to the lightest Kaluza-Klein particle (KK-partner of the photon, for instance) and to super-heavy dark matter candidates (for example SIMPzillas) will be evaluated, both for spin-independent and spin-dependent interactions. In addition, the sensitivity to solar axions will be investigated |
offen BetreuerIn: Sebastian Arrenberg |