Bachelor’s Thesis in Physics

The analysis of experimental impurity densities in fusion plasmas via charge exchange recombination spectroscopy requires an accurate knowledge of the neutral density populations in the plasma. At the ASDEX Upgrade tokamak there are several codes available to calculate these neutral densities, each of which approaches the problem differently. Generally, the neutral densities produced by the codes agree quite well. However, in certain parameter ranges discrepancies have been observed. The objective of this Bachelor’s work is to explore and compare the parameter dependencies of the neutral densities calculated via the different codes. The observed differences are to be quantified and documented and the resultant effect on the calculated impurity densities evaluated.

Contact: Dr. Rachael McDermott

Massive stars occur in groups. Stellar evolution reflects how these stars evolve, change their luminosity, shed winds, ionize their environment, and finally explode as supernovae.

Our population synthesis code implements a small set of classical stellar evolution models, and calculates the time histories of stellar luminosities, mass ejections, and nucleosynthesis ejecta.

The thesis task is to implement new/recent stellar evolution models into this code, and evaluate the impact of the different stellar evolution models, comparing these different time histories.

Die Arbeit wird bei TOPTICA-Photonics in Gräfelfing durchgeführt

Pre-clinical biomedical research often uses small-animal mouse models to study diseases or disease progression. Mostly these animals are then investigated by conventional histopathology. As an alternative, this project will investigate a new microCT imaging protocol for contrast-enhanced (ex-vivo) small-animal imaging, which would yield high-resolution and 3D images of the whole mouse model.  

Character of thesis work: mainly experimental

For more information, please contact: Julia Herzen (julia.herzen@mytum.de, +49 89 289 12550) or Franz Pfeiffer (franz.pfeiffer@tum.de, +49 89 289 12551)

Betreuung: Florian Siegrist, MPQ (für MPQ Notenschnitt von <= 2,0 erforderlich)

Supernova explosions are disruptions of stars, and large amounts of gas are ejected into interstellar space. The explosion itself is characterized by matter at high energies characteristic for nuclear fusion, i.e. MeV energies or GK temperatures. The rapid expansion and cooling leaves behind matter that gradually recombines from the original plasma state. Observations across the electromagnetic range thus show matter at different ionization states in characteristic lines, as well as radioactive decay lines.

  The goal of the thesis is to assemble a multi-wavelength picture of the observational constraints on supernova kinematics for the case of SN2014J, a recent and nearby SN of type Ia.

Die neuesten Entwicklungen in der MPGD Technologie fokussieren sich auf die so genannten `COBRA GEMs`.

Eine COBRA GEM ist eine GEM mit einer strukturierten Elektrode an der Oberfläche, die hilft, den Ionen-Rückfluss sehr effektiv zu Unterdrücken.

Um die Eigenschaften dieser COBRA GEMs in einer TPC-Anwendung zu charakterisieren soll eine umfassende R\&D Studie durchgeführt werden.

Das Ziel dieser Arbeit ist der Bau eines speziellen Detektors, der auf der COBRA-Technologie basiert und das Bestimmen dessen signifikanten Eigenschaften: Energie-Auflösung,

Ionen-Rückfluss Unterdrückung, Entladungs- und Verstärkungs-Stabilität.

Organic light emitting diodes (OLEDs) have received high attention in research and industry due to their broad range of potential applications. With their small film thickness, easy processibility and high image quality, they are already used in flat panel displays and lighting elements.  However, their efficiency and lifetime could still be increased. For this purpose, the properties of the materials used in OLED devices need to be better understood.

This experimental work comprises the fabrication and analysis of additional layers applied for enhancing the performance of OLEDs. Special attention is set to the application of a rough, mesoporous and transparent metal oxide film, which serves as a scattering layer to increase the photon extraction and thereby the efficiency. In an OLED device, it shares an interface with the semitransparent, conducting polymer electrode needed to introduce charge carriers into the photoactive material.  The structure of the scattering layer as well as this interface are of particular interest, as they have a pronounced influence on the performance of the OLED. Characterization techniques include electron and atomic force microscopy, electronic measurements and spectroscopic methods of OLED devices and their components. The light scattering ability of the applied metal oxide interlayer is particularly investigated using angle dependent transmission spectroscopy.

SUPERVISOR: Dr. Michele Burrello, MPI of Quantum Optics, Garching

The geometrical phases and the Berry connection are at the core of our understanding of many phenomena in condensed matter and in the study of topological models.

For example, non-Abelian Berry connections have non-trivial effects on the dynamics of ultracold atoms subject to optically induced potentials and can be exploited to reproduce spin-orbit effects.
Furthermore recent experiments in optical lattices allowed us for the first time to measure Berry connections in momentum space.

In this thesis I propose to study the role of Berry connection and geometrical phases in the engineering of ultracold atom setups and to investigate the possibilities offered by the recent experimental results applied to simple lattice models.

Higher alcohols are attractive fuel additives since they can be blended directly into gasoline. At present, the sustainable production of ethanol from biomass occurs primarily via fermentation. The synthesis of higher alcohols from biomass-derived syngas (mainly CO and H2) represents an interesting alternative, since it allows for the use of a wider range of biomass sources. Still, the lack of efficient catalysts limits the industrial use of this approach.

The focus of the present project is on the catalytic properties of extended metal surfaces for ethanol synthesis. Experimentally, Rh catalysts show some selectivity and activity towards higher alcohol synthesis, though often in modified forms. With the use of computational modeling we aim for an improved understanding of the reaction mechanism on this type of catalysts. In the proposed B.Sc. project, the student will use density functional theory (DFT) to investigate key reaction steps such as C-C coupling steps on different metal surfaces and at different active sites. Also the effect of the local environment in terms of adsorbate-adsorbate interactions will be investigated. The obtained DFT calculations will be used to establish energetic trends in the form of scaling relations and in the end provide the input for microkinetic models such as mean-field and kinetic Monte Carlo simulations. Prior experience with UNIX based operating systems and a scripting language (e.g. Python) is advantageous, but not a prerequisite.

It is well known that light can carry spin angular momentum (SAM), for example via its state of circular polarization. However, it is less widely known that an optical beam can also carry an orbital angular momentum (OAM) via the spatial distribution of the field and the phase across the wavefront. In this case, the wavefront of an optical beam does not only have a phase evolution perpendicular to the propagation direction but can be shaped along the propagation axis into so-called helical, or chiral modes. Such helical beams carry optical angular momentum of mħ, where m is an integer denoting the chirality of the light. The goal of this Bachelor thesis is to use a spatial light modulator which is capable of controlling the phase across the wavefront of a laser beam in order to create beams with different orbital angular momentum. In future experiments, these beams will be used for optical spectroscopy of semiconductor nanostructures.

The Large Hadron Collider in Geneva has restarted its operation at a center of mass energy of 13 TeV. The main purpose for building the LHC is to discover new interactions beyond those of the Standard Model. So far, no new particles - aside from the Higgs boson - have been found. But there is a long future during which the LHC will accumulate a data set about 100 times larger than the current one.

In this thesis, the methods used to search for new particles will be developed using a couple of illustrative examples. Of particular theoretical interest are the implications of existing experimental searches on extensions of the Standard Model of particle physics. Optionally, an existing experimental analysis will be implemented and recast in a new physics model like supersymmetry.

Prerequisites: basic relativistic kinematics, basic knowledge of the Standard Model of particle physics, some affinity with computer programming (e.g. c, c++, python).

Heuslerlegierungen sind eine prominente Klasse funktioneller Materialien mit einem weiten Anwendungsbereich, z.B. als magnetische Formgedächtnislegierungen, magnetokalorische Materialien oder Halbmetalle für Spintronik-Anwendungen. Aspekte ihrer Funktionalität wie z.B. die Arbeitstemperatur hängen empfindlich von der eingestellten atomaren Ordnung ab. In unserer Gruppe beschäftigen wir uns mit der Messung und Beschreibung der damit zusammenhängenden Phänomene und verwenden dabei kalorimetrische Methoden wie auch Neutronen- und Röntgenstreuung. Die theoretisch vorhergesagten Halbmetalle NiCoMnGa und NiCoMnAl sowie das magnetische Formgedächtnissystem Ni2MnAl sind die Systeme, an denen wir im Moment am meisten interessiert sind.

Der Schwerpunkt der angebotenen Bachelorarbeit liegt in der Untersuchung der Ordnungskinetik eines spezifischen Heuslersystems v.a. mittels Differential Scanning Calorimetry (DSC). Während im Fall von NiCoMn(Ga/Al) das Ziel in der möglichen Ordnungseinstellung am B2-L2_1-Übergang liegt, ist es im Fall von Ni2MnAl der Einfluss der Ordnung auf den martensitischen Übergang, wobei auch die Untersuchung verwandter Systeme denkbar ist. Dies ist eine genuin wissenschaftliche Fragestellung, von der Publikation der gewonnenen Erkenntnisse unter Mitwirkung der/des Bachelorkandidaten ist auszugehen.

Kontakt: Michael Leitner michael.leitner@frm2.tum.de, Pascal Neibecker pascal.neibecker@frm2.tum.de

Among other things humanity is facing two problems in the not too far future, global warming due to an overabundance of greenhouse gasses such as CO2 in the atmosphere and the need to transition away from finite fossil fuels to renewable energies. A way to tackle both these problems presents itself in the form of photochemical carbon dioxide reduction, where sunlight is harnessed to convert CO2 to higher energy products such as methanol. Unfortunately, currently available CO2 photo-reduction catalysts all suffer from very low turnover rates and are therefore not suitable for large scale industrial application. In the proposed Bachelor's project, candidates will employ state of the art computational---such as embedded density functional theory/classical mechanics simulations---and theoretical methods developed in the Reuter group to identify efficiency limiting steps and search for more effective photo-catalysts. Existing knowledge of UNIX based operating systems and programming is desirable, but not a necessity.

Physical properties of quantum many-body systems and quantum complexity theory

In quantum complexity theory, an central problem is to determine the ground state energy of a given many-body Hamiltonian up to a certain precision, known as the "local Hamiltonian problem". The goal of this project is to relate the local Hamiltonian problem to physically more relevant questions about many-body systems, such as the behavior of observables, the scaling of correlation functions, or the entanglement entropy of the system. A central tool in this project will be the use of refined perturbative expansions which allow for rigorous error bounds on the perturbative corrections, and which will allow to relate the ground state energy to other physical quantities of interest.

This project is supervised by Dr. Norbert Schuch

(contact: norbert.schuch@mpq.mpg.de)

Ongoing experiments at the Large Hadron Collider (LHC) at CERN explore
heavy ion collisions in an unprecedented energy window, with lead nuclei
colliding now at a centre-of-mass energy of 2.76 TeV per colliding nucleon
pair. The aim of these experimental investigations is the formation of the
Quark Gluon Plasma (QGP), a new state of matter that should originate when
nuclear matter undergoes a phase transition from its normal hadronic state
to a deconfined partonic phase. This transition is predicted by QCD, the
theory of strong interactions, at a temperature of about 170 MeV. Such
studies have important cosmological and astrophysical implications, given
that we believe that the QGP was existing in the early universe, filling
all space a few microseconds after the Big-Bang.
Heavy quarkonium dissociation is one of the phenomena used to obtain
information about the quark-gluon plasma formation in heavy-ion
collisions. Recent theory results based on effective field theories gives
a description of this phenomenon inside a Schrödinger equation with a
complex potential. The aim of this thesis is to study the correct way of
defining the eigenfunctions and eigenvalues for this problem and write a
computer program able to find them numerically at different temperatures.

Für den Betrieb des ATLAS-Detektors am LHC bei hohen Strahlintensitäten wird ein neues Myontriggerkonzept für die erste Triggerstufe entwickelt und erprobt. Die Bachelor- und Masterarbeiten befassen sich mit der Computersimulation des Trigggerschemas und mit der Auswertung von Testdaten.

In der BSc-Arbeizt sollen Studien zur Abhängigkeit der Energie- und Ortsrekonstruktion einzelner Ereignisse im solaren Neutrinodetektor Borexino angefertigt werden. Dazu werden eindeutig zuzuordnende Signale aus Beta- und Alphazerfällen sowie die Einfangsprozesse von Neutronen analysiert. Insbesondere soll der Einfluss der Winston-Cones die vor den ca. 2000 Photomultipliern des Detektors plaziert sind untersucht werden.

Die Arbeit ist Teil des Borexino-Analyse Programms am Lehrstuhl E15. Der/die Kandidat/in wird in der Gruppe integriert sein und von L. Oberauer (Supervisor), S. Appel, D. Jeschke und B. Neumair betreut werden. Vorkenntnisse in C++ bzw. Root sind willkommen aber nicht notwendig. Engagement und Freude am Analysieren von realen Daten eines der besten Neutrinoexperimente weltweit aber schon...

Eines der vorrangigen Ziele des sich im Aufbau befindenden JUNO Experiments in China ist die Bestimmung der Neutrinomassenhierarchie mittels einer präzisen Spektroskopie von Reaktorneutrinos. In der angebotenen Bachelorarbeit sollen systematische Unsicherheiten bei diesem Experiment untersucht werden und deren Einfluß auf die Genauigkeit der Bestimmung der Massenhierarchie quantifiziert werden. Insbesondere sollen die Abhängigkeiten der Messgröße von den Unsicherheiten der bisher bekannten Oszillationsparameter diskutiert werden.

Eines der wichtigsten ungelösten Probleme der Physik ist die Frage nach der Beschaffenheit der dunklen Materie.
Die Peccei-Quinn Symmetrie, die eingeführt wurde, um das sog. starke CP Problem zu lösen (keine CP Verletzung im
starken Sektor beobachtet), liefert einen natürlichen Teilchenkandidaten, der die dunkle Materie erklären
könnte: das Axion. Dieses sollte an Photonen (im GHz Bereich) koppeln können.
Da die Wechselwirkungswahrscheinlichkeit der hypothetischen Axionen extrem gering ist, bedarf es besonderer
experimenteller Anordnungen, um das Teilchen nachweisen zu können.
Ein neues Projekt, das momentam am MPI für Physik entwickelt wird, nutzt
die Idee, mehrere Platten mit hoher Dielektrizitätskonstante vor einer
metallischen Platte in einem straken Magnetfeld anzuordnen. Diese Konfiguration erlaubt es, die Axionen-Photonen-Kopplung
über einen Frequenzbereich von mehreren 10MHz resonant um einen Faktor bis zu ca. 10.000 zu erhöhen.
Dadurch kann eine Axion-Photon Konversionsrate erzeugt werden, die mit Verstärkern der jüngsten Generation nachweisbar sein sollte.
Der genaue Frequenzbereich hängt hierbei von der Positionierung der Platten ab.
Am MPI für Physik wird derzeit ein erstes Vorexperiment installiert, mit demgezeogt werden soll, dass die nötige
Empfindlichkeit erreicht werden kann.


Es werden mehrere Bachelorarbeiten angeboten:
- Transmissionsmessungen für verschiedene Plattenkonstelationen, um zu ermitteln, mit welcher Genauigkeit
die Positionierung der Platten vorgenommen werden muss
- Messung des Vorverstärkerrauschpegels als Funktion der Temperatur 8Raumtemperatur bis ca. 10K)

Am FRM II befindet sich die weltweit stärkste Quelle für monoenergetische Positronen – NEPOMUC.. Die kinetische Energie des sogenannten remoderierten Positronenstrahls lässt sich für Oberflächenuntersuchungen variieren, um die Reemission gekühlter Positronen zu detektieren. Im Rahmen der Bachelorarbeit soll an verschiedenen Einkristallen die Emissionscharakteristik von thermalisierten Positronen gemessen werden.

Für die Myondetektoren des ATLAS-Experiment am LHC bei hohen Protonstrahlintensitäten und damit Untergrundzählraten wird neue schnelle Ausleseelektronikentwickelt. Diese wird im Labor und unter intensiver Gammabestrahlung am CERN getestet. Die Bachelor- und Masterarbeit befasst sich mit Durchführung und Auswertung dieser Testmessungen.

Recent conceptional and technical progress makes it possible to prepare and explore strongly-correlated non-equilibrium quantum states of matter. Such states can be very well controlled in synthetic quantum matter, such as ultracold atoms, trapped ions, or quantum dots. However, theoretically many facets of non-equilibrium states are not well understood. Among them are thermalization in closed quantum systems, dynamic phase transitions, and intertwined order far from equilibrium. In this project we will explore state of the art questions of the field of nonequilibrium quantum dynamics that are also of direct relevance to current experiments.

The electromagnetic interaction between two neutral systems is the
so-called Van der Waals force. Van der Waals interactions are the result
of the interaction between instantaneous dipole moments in the atoms. Two
different regimes have been known for a long time. The short range regime
appears when the momentum transfer between the two neutral atoms is larger
than the excitation energy of the instantaneous dipole. This case is known
as the London force, who was the first to develop it in the 1930. The
London force is characterized by a dependence of R^6, where R is the
distance between the neutral atoms. The long range regime appears in the
opposite conditions, that is, when the momentum transfer between the atoms
is much smaller than the excitation energy of the instantaneous dipole.
These is usually referred as the Casimir-Polder force, who developed it in
the 1948. The Casimir-Polder force depends on the distance like R^7.

An unified description of the different regimes of Van der Waals forces
stemming from first principles can be obtained by employing effective
field theory techniques. The basic idea of effective field theories is
that the dynamics at low-energies do not depend on the high energy
dynamics. Furthermore the effective field theory description allows for a
theoretical description of the polarization factors previously
unavailable. The polarizations are given in terms of a series of the
expected values of the position and spin between the atomic wave functions
of initial state and the instantaneous exited states over all the exited
states. The aim of this thesis is to compute the instantaneous
polarizations of the hydrogen atom and to study the variation for initial
states with different angular momentum as well as to determine if there is
a dominant contribution corresponding to a determinate excited state.
Applications of these findings ranging from strong interaction to dark
matter will be discussed.