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; measurements of fundamental properties of liquid xenon as a radiation detection material with small detectors in our lab; material radioassay with a high-purity Ge detector (Gator) LNGS; hardware, MC simulations and data analysis for Qrocodile, an SNSPD-based dark matter experiment; data analysis of XENONnT and LEGEND-200 data; hardware, MC simulation and analysis projects for Xenoscope, a liquid xenon platform in our laboratory.

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

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

SNSPD characterisation for dark matter searches with QROCODILE

Our group is involved in low mass dark matter searches with superconducting nanowire single-photon detectors (SNSPDs). When a particle interacts in the wire or the substrate it creates a resistive hotspot that increases the critical current, detected as a pulse by the readout. We operate the sensor at very low temperature (~100 mK) in the superconductive region, using a dilution cryostat here at UZH. Join us in characterising a new chip of nanowires; you will participate in the cryostat operations, in the characterisation of the sensor with an Fe55 source and a laser and in the subsequent dark matter run!

You can find more info on the QROCODILE (Quantum Resolution-Optimized Cryogenic Observatory for Dark matter Incident at Low Energy) experiment and SNSPD on thewebsite

Contact: chiara.capelli@physik.uzh.ch

Shine bright like a diamond

Dual-phase liquid xenon time projection chambers (TPCs) are at the forefront of particle detectors used to search for the enigmatic dark matter in our universe. To detect a dark matter interaction inside these cryogenic detectors, they rely on the propagation of electrons liberated by particle interactions. This requires the application of an electric drift field. To ensure proper reconstruction of interactions in the detector, the homogeneity of this field needs to be ensured. Traditionally, this is achieved with a field-cage made of individual field-shaping rings. However, we are pioneering a novel approach of using a low-conductivity surface coating on insulating materials such as PTFE. An ideal candidate for such a coating is diamond-like carbon (DLC), which is a very fascinating and versatile material. Your task will include conceptual design, electric field simulation using COMSOL Multiphysics, and testing the sheet resistivity and adhesion of DLC coatings at cold temperatures. If time allows, we will study the reflectivity of such a coating to the light produced by particle interactions in the liquid xenon.

ContactDr. Florian Jörg

Radiogenic Background Simulations for XENONnT & XLZD

Experiments using liquid xenon are at the forefront of direct dark-matter searches. To reach their sensitivity, they require a precise understanding of radiogenic backgrounds originating from detector materials and the experimental environment (rock, concrete, infrastructure). Monte Carlo simulations are essential to quantify these backgrounds and to guide design and material selection.

Project overview: You will develop and run Geant4-based simulations to model radiogenic backgrounds for the XENONnT detector and the proposed next-generation XLZD observatory. The work will benchmark and integrate existing software tools into our Geant4 framework, validate the model against assay data and calibration runs, and produce background budgets relevant for dark matter and related physics channels.

What you will learn: Geant4 for rare-event detector simulations; best practices for low-background modeling; data analysis in Python/ROOT; how background predictions inform detector design and sensitivity.

Contact Dr. Jose Cuenca

Modeling Charge Drift and Diffusion Effects on Pulse Shapes in LEGEND-200 HPGe Detectors

This project will investigate charge drift, diffusion, and self-repulsion effects on pulse shapes within LEGEND-200's germanium detectors. You will use SolidStateDetectors.jl to simulate charge carrier drift paths, integrating models for temperature-dependent mobility and anisotropic drift in germanium. The project will explore the influence of charge diffusion and self-repulsion on pulse formation, aiming to refine signal generation accuracy.
Objectives:

• Develop simulations of electron and hole drift under various electric field strengths
• Quantify the impact of diffusion and self-repulsion on pulse shape accuracy
• Validate the simulations with experimental data to improve model reliability

Contact: Dr. Marta Babicz