Bachelor’s Thesis in Physics

Pattern formation in cell layers is experimentally studied in both biological and synthetic systems. For instance, in developmental biology, the correct relative positioning of different cell types is essential to ensure that the organism functions correctly. This project will explore some of the underlying physical concepts with a theoretical approach. Whilst many models for pattern formation exist, the focus here is on cellularized systems with interactions only between neighboring cells. This form of communication has previously received less attention from theoretical research than e.g. long-range diffusible signals as a means of communication. Our goal is to explore fundamental limits and patterning concepts with a simple top-down model based on cellular automata. Building on previous work, the project will concentrate on exploring mechanisms of pattern formation with the goal of investigating how cell division and cell death can influence pattern formation in tissues and how tissue regeneration following damage can be achieved. Successful work on this project requires some background in the concepts and methods of statistical physics, as well as skills in computational problem solving.

Lithium ion microbattery is the type of battery where all components (electrodes, membrane, and packaging) are in the thin film format. The need for such types of batteries is to provide light-weight and shape flexible solid-state energy sources for some miniature medical devices, such as implantable pumps, biosensors, and wireless capsule endoscopes. Membrane based on mixing both lithium slat and polyelectrolyte block copolymers will be prepared and investigated using small-angle X-ray scattering and impedance spectroscopy. The effect of a third component such as inorganic SiO₂ nanoparticles on the morphology and conductivity of the prepared thin film membranes will be studied. The best performing membrane will be assembled between two electrodes to probe the performance of a complete assembly of a solid-state lithium battery. The project will involve a literature review, sample preparation, x-ray scattering and impedance spectroscopy.

You will develop novel integration algorithms in high-dimensional spaces.  Possibilities include various forms of importance sampling algorithms and the further development of the Adaptive Harmonic Mean Integration algorithm using differently chosen volumes for integration.  Test problems will be chosen from physics projects to validate the algorithm.  Good programming skills and knowledge of linear algebra are a pre-requisite for the project.

Josephson junctions (JJs) represent a fundamental building block of modern quantum circuits such as superconducting qubits or Josephson parametric amplifiers. The JJs are conventionally fabricated with Al while the surrounding quantum circuits are often made of Nb. Henceforth, there is a need of galvanic connection between them which includes removing Nb oxide via ion milling.  As a consequence, one needs to develop a careful milling and fabrication technique in order to preserve a low-loss microwave environment in the close vicinity of JJs. This task is of paramount importance for achieving high coherence times of the related quantum devices.

The goal of this Master project is to develop a fabrication technique for Al/Nb superconducting circuits which will include Ar/O2 milling. This also includes cryogenic microwave studies of fabricated superconducting circuits (such as Josephson parametric amplifiers and transmon qubits) and participation in experiments towards quantum information processing with superconducting devices.

Planar superconducting microwave resonators are key for the ultra-sensitive detection of spin properties. We employ planar microwave resonators fabricated from various superconducting materials like Nb, NbN and NbTiN and test their performance with respect to field and temperature stability. With your help, we aim to improve our existing variable temperature setup operating between 1.5 and 300K. In detail, you shall assemble a new measurement inset including a cryogenic microwave amplifier, and asses the overall performance of the setup using electron spin resonance. Moreover, you shall further optimize microwave resonators to improve their quality factors.

Your bachelor thesis will bring you in touch with state-of-the-art microwave spectroscopy tools like vector network analyzers, as well as cryogenic measurement environments. In addition, you will fabricate and optimize microwave resonators and perform the microwave spectroscopy measurements. Moreover, the careful data analysis of the magnetic field dependent datasets will put you in the position, to make a meaningful impact on microwave resonator technology

The extreme environment in a fusion plasma reactor, especially the heavy load with hydrogen, leads to various unexpected effects. The Plasma Component Interaction research group at the Max Planck Institute for Plasma Physics (IPP) investigates these effects. One material system of interest is the Fe-W system, which exhibits tungsten enrichment on the surface under hydrogen bombardment. In order to separate the underlying mechanisms and their contribution, well-characterised model samples will be prepared and treated (annealed, ion beam bombarded) and their response to these treatments will be analysed by ion beam analyses and scanning electron microscopy. This thesis should contribute to answering the question: Does ion- and/or hydrogen-enhanced segregation exist in the system Fe-W?

Contact: Dr. Martin Balden

NEPOMUC provides the world’s most intense positron beam. The positron is a applied as unique probe for material defect studies, surface investigation and fundamental research in quantum physics.
For the experiments we typically use electrostatic acceleration to implant the positrons in the material, with the sample holder being charged to tens of kilovolts with respect to ground. In these conditions it is extremely difficult to subject the sample to electric currents or potentials during the measurement, which limits the use of e+ for novel in-operando studies relevant for the construction of batteries, solar panels and integrated electronics.
At NEPOMUC we are now developing an active sample holder which makes use of light to
both power its onboard instrumentation and to communicate with the control system.
As an applicant you will be tasked, with the support of the NEPOMUC team and the TUM
facilities, to build a prototype of such sample holder, test it and program its onboard MCU.
The work will involve the following tasks:

1. Progressive assembling of the sample holder, performing electrical tests to ensure functionality after every assembling step.
2. Programing the onboard MCU and running all of the subsystems of the sample holder in a test environment.
3. Designing a control protocol to be run over an IRDA optical bridge and implement it.
4. esting the autonomous functioning of the sample holder, with the system being powered through light and communicating through an optical bridge.
5. Testing the system in UHV conditions with a 30 kV bias applied.

As an applicant you will be given the opportunity to experience first hand the development of
highly specialized scientific equipment. We attach particular importance to the training aspect
during the internship; as such you are not required to be able to carry out the entire task by
yourself, but you will be helped and tutored by our team. This said a certain level of autonomy
is expected from you.

Porennetzwerk in porösen Medien sind integraler Baustein von Reaktionszellen, die den Kern für Photokatalyse, Gassensorik und Lithium-Ionen-Batterien in Brennstoffzellen bilden. Der Transport durch ungeordneten porösen Medien wird durch die exponentielle Verteilung von Strömungsgeschwindigkeiten grundlegend eingeschränkt, da in großen Bereichen nur geringe Strömungsgeschwindigkeit vorliegt. Mit dem Ziel gezielt Strömung durch poröse Medien zu verbessern soll hier ein geometrisches Mass für die  Unordnung in porösen Medien gefunden werden. Dazu werden Sie laminier Strömungen in porösen Medien mit einfachen Matlab Programmen simulieren und quantifizieren, wie sich Änderungen im Porennetzwerk auf Strömungen auswirken. Einfache analytische Modelle zu Strömungen in Porennetzwerken werden Ihnen dabei helfen ein Mass für die Unordnung in porösen Medien zu finden.

Pore networks in porous media are integral components of reaction cells, which form the core for photocatalysis, gas sensor technology and lithium-ion batteries in fuel cells. The transport through disordered porous media is fundamentally restricted by the exponential distribution of flow velocities, since only low flow velocity is present in large areas. With the aim of improving the flow through porous media, a geometric measure for the disorder in porous media is to be found here. For this purpose you will simulate laminated flows in porous media with simple Matlab programs and quantify how changes in the pore network affect flows. Simple analytical models of flows in pore networks will help you to find a measure for the disorder in porous media.

Pattern formation in cell layers is experimentally studied in both biological and synthetic systems. For instance, in developmental biology, the correct relative positioning of different cell types is essential to ensure that the organism functions correctly. This project will explore some of the underlying physical concepts with a theoretical approach. Whilst many models for pattern formation exist, the focus here is on cellularized systems with interactions only between neighboring cells. This form of communication has previously received less attention from theoretical research than e.g. long-range diffusible signals as a means of communication. Our goal is to explore fundamental limits and patterning concepts with a simple top-down model based on cellular automata. Building on previous work, the project will concentrate on investigating how the interaction range between cells can influence the ability to realiably create typical biological patterns such as a heterogeneous stripe-pattern. Successful work on this project requires some background in the concepts and methods of statistical physics, as well as skills in computational problem solving.

Find the best strategy to measure the width difference ΔΓ between even and odd CP eigenstates of the B⁰_d comparing various analyses methods, e.g. :

Two component fit, weighting, moments, multi-parameter log-likelihood fit, etc.

The major component of conventional paper are cellulose fibers. With cellulose nanocrystals or microfibrils the manufacturing of thin transparent layers is possible. These layers serve as sustainable substrates in flexible applications. We aim for functional films which reversibly change the color with irradiation of UV-light. Composite films of cellulose and inorganic nanoparticles will be prepared by advanced deposition methods including spray deposition and slot die coating. The project will involve a literature review, sample preparation, x-ray diffraction studies and UVvis spectroscopy.

Am Positronenexperimente zur Defektsusheilung in Kristallen bei hohen Temperaturen mittels eines neuartigen LED-Heizers FRM II existiert mit NEPOMUC(Neutron-induced Positron source Munich) die Anlage mit dem weltweit intensivsten Positronenstrahl. Um mit diesem Strahl insbesondere Kristalldefekte und deren Ausheilung zu untersuchen  ist ein heizbarer Probenhalter notwendig. Da mittlerweile kostengünstige LEDs mit hoher Lichtstrom (> 1.1 × 10
4lm bei 100 W Leistungsaufnahme) verfügbar sind, soll ein neuer Probenhalter gebaut werden, um Temperaturen von mehr als 1300 K zu ermöglichen. Nach erfolgreichem Aufbau soll das Ausheilverhalten verschiedener Metallproben mit in-situ Positronenannihilationsspektroskopie gemessen werden.

Die Arbeit gliedert sich in folgende Abschnitte:

1. Konstruktion eines Hochvakuums-, Hochspannungs- und Hochtemperaturfähigen Aufbaus
   
2. Einbau und Inbetriebnahme am Spektrometer vor Ort
3. Messung des Ausheilverhalten von Kristalldefekten in Metalleinkristallen

Perovskite solar cells have dramatically progressed within the last 2 years. Meanwhile championship perovskite solar cells have demonstrated efficiencies above 25%. The general intent of this work is to optimize printed perovskite thin-films for high-quality photovoltaic devices. This will include material and solution preparation, optimizing the printing process and analysis of printed films and/or devices. Analytical methods will focus on film morphology, spectroscopic material properties, crystal structure analysis and current-voltage measurements of self-built solar cells. The thesis also includes a brief literature review.

Amphiphilic block copolymers having a permanently hydrophobic block and a thermo-responsive block form nanoparticles, or rather core-shell micelles, in aqueous solution. The structure of these micelles is controllable by changing the temperature or the ratio between the hydrophobic and the hydrophilic block. These properties enable amphiphilic block copolymers as candidates for a wide variety of applications, such as drug delivery. The main goal of this thesis is to investigate above which polymer concentration micelles form and to characterize the size of the micelles by fluorescence correlation spectroscopy.  For more information, please contact Prof. Christine Papadakis, papadakis@tum.de.

In nature, quarks and gluons cannot exist as free particles. They are always confined into hadrons. Unfortunately, the equations of the strong interaction that governs the behavior of quarks and gluons cannot be directly solved at energy scales where hadrons form. Hence theoretical predictions of hadron properties such as their masses and decay modes are very difficult. This is in particular true for hadrons that are made of the three lightest quarks: „up“, „down“, and „strange“. Also on the experimental side much confusion exists on what concerns masses, decay widths, and the assignment of quantum numbers of some observed hadrons, let alone the interpretation of their internal structure.

Our group participates in the COMPASS experiment at CERN, where we study the production of mesons (hadrons with integer spin) in the scattering of a 190 GeV pion beam off a stationary proton target. The produced highly excited mesons have extremely short life times of the order of 10^-24 seconds and can hence be measured only via their decay products. Our group employs and develops mathematically involved statistical analysis tools in order to identify the produced mesons with high sensitivity and to measure their properties with high precision. We have recently found a new meson with surprising properties and also did groundbreaking work on precision measurements of the properties of the pion. This science addresses one of the last open questions of the Standard Model of particle physics, which is the understanding of the strong force at large distances and low energies.

We offer thesis topics, which cover a wide range of subjects in strong-interaction physics, statistics, and/or computer science. The thesis work can start at different levels within the analysis chain: from the selection of a reaction process itself up to the final fitting process leading to scientific publications. The topic can be chosen according to personal preference and interest.

Experience in computer programming is helpful, but not required.

Contact: Boris Grube bgrube@tum.de, room PH1 3574, Tel. 089 289 12588

Outline, calculation and design of a purification cryostat to produce isotopically pure He-4 out of natural helium in a continuous manner based on the superfluid heat flush principle.

The FRM II is presently testing and will subsequently install a source to produce ultra-cold neutrons (UCN) in the reactor. In the central section of this UCN source, helium is used for cooling. By passing through, the cooling agent helium will be irradiated by neutrons, which create radioactive tritium out of the He-3 portion. This negative side effect can be avoided respectively reduced to a permissible level if isotopically purified He-4 with no traceable He-3 content is used.

Sources for isotopically pure He-4 are scarce and availability varies with market demand. In order to ensure continuous operation of the UCN source the availability must be secured. For this reason such an isotopic purifier shall be build.

In this thesis the thermodynamical properties of the purifier shall be simulated with COMSOL.

Contact / Supervisor:

Dr. Andreas Frei, Tel. 089 289 14260, andreas.frei@tum.de

Magnetic Weyl semi-metals combine magnetic order and a topological electronic band structure. It is expected that mutual spin-to-charge conversion is particularly efficient in these materials. We will study mutual spin-to-charge conversion using methods of ferromagnetic resonance.

Gamma-ray bursts (GRBs) are flashes of gamma-rays resulting from the death of massive stars or the merger of neutron stars. The latter also produce gravitational waves. The presently most prolific GRB detector is the "Gamma-Ray Burst Monitor" (GBM) on the Fermi satellite, containing 12 NaI scintillation detectors. The position is derived by comparing the relative count rates in the differently oriented scintillator planes.

This thesis shall use existing flight data of the brightest gamma-ray source on the sky (the Crab nebula) and improve the spatial resolution of the response matrix of selected detectors. The result shall be tested by localizing selected GRBs with GBM, and comparison against known positions of these GRBs from other satellites (e.g. Swift).

Technically, this thesis involves learning of (i) learning the basics of GRBs, (ii) data analysis of non-imaging gamma-ray detectors, (iii) understanding and correcting detector effects, (iv) fitting light curves with different count statistics, and (v) analyzing and combining large amounts of individual constraints into a coherent picture.

Some background in astrophysics is advantegeous. Python knowledge is required, and good programming skills. Joy in data analysis is required.

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

In 2011, a new solid lithium electrolyte was reported, featuring liquid-like Li-ion conduction in a crystalline solid matrix. The ultrafast room temperature transport of tetragonal Li10GeP2S12 (LGPS) with a conductivity of several mS/cm exceeds the values of most crystalline Li conductors by one order of magnitude. Accordingly, there has been a strong search in realizing LGPS-type materials based on the homologous elements Si and Sn. LXPS (X=Ge,Sn,Si) electrolytes appear in a tetragonal and orthorhombic modification. While the orthorhombic phase is an undesired inpurity in the LGPS electrolyte, orthorhombic LSPS leads to an enhancement of the conductivity. A possible explanation of the increased conductivity,
is an interplay of orthorombic and tetragonal LSPS, which distorts tetragonal LSPS. This distortion may lead to a favorable opening of Li-channels. The aim of this work is to investigate the effect of distortion on the materials conductivity for tetragonal LSPS. To do so a machine-learned force-field will be provided. The project will start with the construction of distorted LSPS structures and will then focus on Molecular Dynamics (MD) calculations for appropriate LSPS ensembles at finite temperatures. Finally, the conductivities will be calculated via the Nernst-Einstein relation.

Das LEGEND Experiment wird z.Zt. zur Suche nach nutrinolosem
Doppelbetazerfall mit Hilfe von Germaniumdetektoren augfgebaut.
Die LEGEND Gruppe am MPI untersucht in Muenchen zur Vorbereitung
der Analysen in speziell konzipierten Teststaenden
die fundamentalen Eigenschaften der Ladungstraeger in Germanium.
Zur Simulation von Halbleiterdetektoren hat die Gruppe u.a.
das open-source Programmpaket SSD.jl entwickelt.
Bachelorarbeiten koennen vergeben werden fuer
 -- spezialisierte Datennahme und Qualitaetskontrolle,
 -- Simulation von bestimmten Detektorkonfigurationen,
 -- Arbeiten am SSD.jl Paket [incl. Einarbeitung in die Sprache Julia],
 -- Simulationen fuer die Physik von LEGEND.
Interessenten moechten bitte Dr. Iris Abt [isa"at"mpp.mpg.de] und
Dr. Oliver Schulz[oschulz"at"mpp.mpg.de] kontaktieren.

The combination of quantum mechanical calculations and machine-learning techniques has led to massive advances in the high-throughput computational screening of materials and molecules. Here, it is frequently stated that training data obtained from quantum mechanical simulations (e.g. using density functional theory) is 'noise-free', because the calculations can be numerically converged to very high precision. However, this assumes that the self-consistent algorithm used to calculate the Kohn-Sham determinant always converges to the correct ground-state solution, which is by no means guaranteed. The goal of this project is to quantify the noise introduced into DFT data by different choices of intital guess and convergence acceleration. To this end, the true ground-state solutions for a representative set of molecules will be determined using wavefunction stability analysis. This benchmark will allow the development of an effective 'black-box' method for obtaining well-converged training data. Furthermore, the effect of noise on quantum mechanical machine-learning applications will be studied.

The candidate should be interested learning the fundamentals of density functional theory and supervised machine learning. The project will require the development of automated workflows for high-throughput electronic structure calculations and data analysis. Experience with a scripting language (e.g. Python) and UNIX operating systems is advantageous but not mandatory.

Questions about the project can be directed to johannes.margraf@ch.tum.de.