We offer several topics for bachelor and master theses within the framework of our research projects. Examples are: tests of new photosensors in liquid xenon and argon at UZH; material screening with a high-purity Ge detector (Gator) LNGS; data analysis of XENONnT and LEGEND-200 data; MC simulations for the DARWIN demonstrator, for XENONnT and for LEGEND; hardware and computing projects in the framework of Xenoscope, a full-scale vertical DARWIN demonstrator at UZH.

Please have a look at our research page and contact one of us for details and the timescales of possible projects.

 

Master thesis project: A new method for calibrating photosensor responses in direct dark matter searches

Xenon-based dark matter detectors such as XENONnT aim to detect the faint signals from dark matter particles interacting with xenon atom. The light released in such interactions is registered by photomultiplier tubes (PMTs) that can detect single photons by converting them to millions of electrons that can be registered as an electrical current. The photon to electron conversion factor is called gain and needs to be known precisely for data analysis in the experiments. Traditionally, the gain is determined using a faint artificial light source in a detector such as an LED. Since this calibration requires pausing the dark matter search, it is only carried out on the timescale of weeks. Short-time variations in gain cannot be monitored in this way. This master thesis looks at a new method for continuous gain calibration that uses thermally-induced signals in the PMTs as well as background-photons. As these are always present in the detector, they can augment the dedicated gain calibrations and provide more precise gain estimates for the world’s most sensitive dark matter detectors. The thesis work will allow the student to get an in-depth look at data analysis in the XENONnT dark matter experiment. It entails data-analysis, statistical inference of PMT parameters and simulations.

Contact Dr. Christian Wittweg

 

Master thesis project: Shining light on trace impurities in liquid xenon

Liquid xenon detectors located deep underground are on the forefront of our ongoing effort to detect dark matter particles. They rely on the detection of very faint light signals which are emitted in the interaction of the dark matter particles in our detector. Since certain impurities such as water can attenuate this light, an exceptional purity level of the liquid xenon is required. Traces of water in gaseous xenon can be detected using cavity ring-down spectrometry (CRDS). This technique works by bouncing a laser beam back and forth inside a cavity filled with the test gas and measuring its attenuation. In this work, you will be responsible for the integration of a commercial CRDS device (HALO KA - M7500-S) into our local large-scale liquid xenon detector (Xenoscope). The skills you will acquire during this work are widely applicable inside, as well as outside of academia. Among others, you will gain knowledge in operation and maintenance of a high-flow gas handling system, integration of hardware components into automated process control frameworks as well as trace impurity analysis of ultrapure gases.

Contact Dr. Florian Jörg