Bachelor’s Thesis in Physics

Optomechanics is an extremely exciting field where the tiniest motions of mechanical resonators are measured with the help of laser light. So far, most of these experiments have been done with beams and cantilevers, in other words with one-dimensional structures. In the Quantum Technologies Lab we have just build a new setup, where we can measure the vibrations of 2D mechanical systems.

The goal of this project is to explore the world of 2D optomechanics. For this, we have two kinds of samples in mind: one is made from silicon nitride, which is a material with extremely high quality factors. This material is not only used in the manufacturing process of chips, but is also a great material to do optomechanics with. The other direction is to use materials that are just a few atoms thick: This includes graphene, boron nitride, and sandwiches of these true 2D materials. For this, we collaborate with the Karlsruhe Institute of Technology.

We will make the samples for you in the cleanroom, and it will be your goal to measure them with our new setup. This includes their optical characterization, as well as electrical measurements in the time domain (oscilloscope) and in the frequency domain (network- and spectrum analyzer). For the measurement and data processing, we already have a range of computer programs available in our group, so that you can start measuring right away. Depending on your preferences, the project could be completely experimental, or also contain a modelling component.

The project is envisioned with students in Applied and Engineering Physics (AEP) and Condensed Matter Physics (KM) in mind, but if you follow another track we are still interested to hear from you. Being curious and wanting to get a feeling for what doing real research is about, is the most important factor. There are no formal requirements on courses taken.

The measurement of concentration profiles of elements as function of depth is important in many fields of materials science and physics. An important and often employed class of depth profiling methods uses sputter depth profiling, i.e. a beam of (typically heavy) energetic ions ejects particles from the sample and proceeds into depth by removal of material. The ejected particles can be detected by various methods, for example by secondary ion mass spectrometry (SIMS) or glow discharge optical emission spectroscopy (GDOES). While these methods are well established for smooth surfaces, their applicability on rough surfaces or multi-phase materials is more questionable and matter of debate since years. The increase of computing power during the last years enables the dynamic simulation of sputter depth profiling methods on three-dimensional surfaces using the existing code SDTrimSP-3D. This code will be used to model depth profiling on rough surfaces. The modeled results will be compared to existing experimental data.

Contact: Dr. Matej Mayer

The CRESST (Cryogenic Rare-Event Search with Superconducting Thermometers) experiment operated at the Gran Sasso underground laboratory employs highly sensitive cryogenic detectors to the search for signals of the elusive dark matter particles, a main ingredient of the Universe whose nature is still unknown. 

The energy thresholds reached in CRESST-III are the lowest in the field, making CRESST the most sensitive experiment to light dark matter. Optimisation of the tungsten thin-film thermometers and of the techniques for data analysis promise still improvement in energy threshold, which could significantly boost the physics reach of the experiment.

Scientific topics

A student can contribute to:

- design, production and prototyping of new CRESST detectors in Munich 

- development of high purity crystals 

- development of new software tools for data analysis

- dark matter data analysis

and, if interested, can participate in the operation of the main experiment at Gran Sasso. 

Thesis can be carried out at the Max-Planck-Institute for Physics (MPP) und supervision of Dr. Federica Petricca (petricca@mpp.mpg.de) and/or at the Physics Department.

In Garching wird das Großexperiment ASDEX Upgrade betrieben. In diesem Tokamak Experiment werden heiße Plasmen mit starken magnetischen Feldern eingeschlossen. Um die Dichte des Plasmas zu kontrollieren, ist die Bestimmung des Neutralgasdrucks in der Maschine von entscheidender Bedeutung. Hierfür werden sogenannten ASDEX Ionisationsmanometer eingesetzt. Für die genaue Bestimmung der Teilchendichte aus den Messsignalen ist eine Kalibration erforderlich, welche die zentrale Aufgabe dieser Bachelorarbeit darstellt. Die Kalibration erfolgt direkt mit den in ASDEX Upgrade eingebauten Manometern. Zur Aufgabenstellung gehören die Automatisierung des Kalibrationsprozesses, die Begleitung der Kalibrationsexperimente an ASDEX Upgrade und die Auswertung der Daten. Wir erwarten eine ausführliche und wissenschaftlich exakte Dokumentation der Forschungsergebnisse sowie die Bereitschaft sich mit komplexen Fragestellungen auseinanderzusetzen. Programmiererfahrung (v.a. in Python) wäre vorteilhaft.

Contact: Dr. Michael Griener

The COMPTEL instrument measured the 0.7-30 MeV emission of the sky for nearly 10 years in the 90ies. This energy range includes interesting nuclear lines from elements which are produced in the winds of massive stars, or in supernova explosions. In addition, the instrument is a perfect polarimeter - and X-/gamma-ray polarimetry is still considered the holy grail of astrophysics. Even now, 20 years later, its data are unique, and no future mission is on the horizon for the next 20 years. However, our computational tools have drastically improved, allowing analysis types which were completely impractical at the time COMPTEL was operated.

This thesis shall take our mass model and perform GEANT4 simulations for two cases: (i) line emission from stellar gamma-ray sources, and (ii) polarized continuums emission. Based on the simulated data, new cuts in the multi-dimentional data space should be found which separate background photons from source photons. Finally, these cuts should be applied to a test data set of COMPTEL in order to evaluate the improvement in the performance.

Technically, this thesis involves learning about (i) data analysis of Compton gamma-ray detectors, (ii) understanding detector effects, (iii) simulating an observation with different levels of statistics, and (iv) characterizing a multi-dimentional parameter space using e.g. principal component analysis.

Some background in astrophysics is advantegeous, and experience with GEANT4 would be perfect. Some Python knowledge is required. Joy in data analysis is required.

Contact: Jochen Greiner, jcg@mpe.mpg.de, MPE Room 1.3.13, Tel. 30000-3847

Next step fusion devices, such as the currently built major experiment ITER in France, will face a new challenge by exhausting the generated alpha-particle fusion power through the so-called diverter target tiles. Two of the key parameters to characterize this divertor heat load in improved confinement modes are the inter-ELM decay length and the ELM induced energy fluency. The heating method of today’s devices and the burning plasma in ITER are different in many respects. For this reason, it is envisaged to characterize the two key quantities with different heating mixes in ASDEX Upgrade to investigate to which extent the heating method by itself causes variations. Corresponding discharges are executed in IPP’s fusion device ASDEX Upgrade already, optimized for this kind of analysis, and shall be analyzed using infra-red measurements.

Contact: Dr. Thomas Eich

Rare event searches looking for neutrino and dark matter interactions are performed with highly sensitive detector systems, often relying on scintillators, especially liquid noble gases, to detect particle interactions. Detectors consist of structural materials that are assumed to be optically passive, and wavelength-shifting materials that absorb photons and re-emit them at wavelengths where their detection is more easy or efficient. MSc theses are available related to measuring the wavelength shifting efficiency of a number of materials that might be used in future detectors. Furthermore, measurements to ensure that presumably passive materials do not re-emit photons, at the low level relevant to the detectors, can be done. Part of the thesis work can include Monte Carlo simulations and data analysis for current and upcoming dark matter detectors, to study the effect of different levels of desired and nuisance wavelength shifting. In this project, students will acquire skills in photon detection, wavelength shifting technologies, vacuum systems, UV and extreme-UV optics, detector design, and optionally in C++ programming, data analysis, and Monte Carlo techniques.
The work will be done in the context of the DarkSide-20k/DEAP-3600 and LEGEND nternational collaborations. This work is done in close collaboration with institutions in Canada, Poland and in Italy with the option of visiting the collaborating institutions. Students have the chance to practice communicating physics results to other students and experts from many different institutions by presenting their work in bi-weekly project-wide phone-conferences.

Der Large Hadron Collider (LHC) bietet eine einzigartige Gelegenheit, nach Teilchen der Dunklen Materie zu suchen. Sie machen sich im Detektor durch sogenannte fehlende Energie bemerkbar. Zusaetzlich muessen jedoch bekannte Teilchen als Signal erzeugt werden. Dafuer eignen sich besonders gut Hadronjets, die durch Gluonabstrahlung im Anfangszustand haeufig erzeugt werden, aber auch Eichbosonen und sogar das Higgs-Boson. Die Auswahlkriterien fuer solche Ereignisse werden mit Hilfe simulierter Daten optimiert.

Quantum communication promises secure communication and, in combination with quantum computing, eventually a quantum internet. The tremendous success of superconducting circuits for quantum computing has triggered the exploration of quantum microwaves for communication and illumination applications. In this Bachelor’s thesis, you will explore the potential of commercial superconducting cables for the transmission of quantum information over longer distances. In particular, you will characterize cables and low-loss connection techniques with respect to their suitability for quantum teleportation and quantum state transfer.

Keywords: Quantum communication, quantum microwaves, quantum teleportation

Disorder has a drastic influence on transport properties. In the presence of a random potential, a system of electrons can become insulating; a phenomenon known as many-body localization (MBL) that has been envisioned by the Nobel laureate Phil Anderson. However, even beyond the vanishing transport such systems have very intriguing properties. For example, many-body localization describes an exotic state of matter, in which fundamental concepts of statistical mechanics break down. In this project we will explore these exciting aspects of many-body localization.