Prof. Dr. Ulrich Stroth

Photo von Prof. Ulrich Stroth.
Telefon
49 89 3299 2141
Raum
Physik I: 2248
E-Mail
ulrich.stroth@tum.de
Links
Homepage
E2M am IPP
Visitenkarte in TUMonline
Arbeitsgruppe
Plasmarand- und Divertorphysik
Funktion
Professur für Plasmarand- und Divertorphysik
Sprechstunde
nach Vereinbarung

Lehrveranstaltungen und Termine

Ausgeschriebene Angebote für Abschlussarbeiten

Characterization of limit-cycle oscillations with small amplitudes in ASDEX Upgrade plasmas

In the edge of magnetized fusion plasmas, self-generated transport barriers occur which lead to desired confinement improvements if a critical heating power is exceeded. Slightly below the critical heating power threshold, a plasma state is observed featuring limit-cycle oscillations with small amplitudes in magnetic signals. In order to identify the physical origin of this quasi-oscillatory state and the relation to improved confinement regimes, a characterization by means of different plasma diagnostics has to be performed. This work includes participation in new experiments at the ASDEX Upgrade Tokamak located at the Max Planck Institute for Plasma Physics and software development for data analysis in Python.

Contact: Dr. Gregor Birkenmeier

geeignet als
  • Masterarbeit Kern-, Teilchen- und Astrophysik
  • Masterarbeit Applied and Engineering Physics
Themensteller(in): Ulrich Stroth
Development and implementation of an average Zeff measurement for ASDEX Upgrade plasmas

In fusion plasmas the parameter “Zeff” is the average ion charge and a measure of the cleanliness of the plasma. Although it is a quantity of interest to almost all physics analyses, it is often not well known and, at the ASDEX Upgrade (AUG) tokamak, there is no routine measurement of Zeff available. There are two standard approaches to determining Zeff. First, the densities of dominant impurities in the plasma can be individually measured and then combined to calculate Zeff. And second, the background Bremstrahlung radiation of the plasma, in combination with the measured electron temperature and density profiles, can be used to gain information on Zeff. The objective of this Master’s work is to first identify measurements of the background plasma radiation that are dominated by Bremstrahlung emission and to use these to provide a routine measurement of the average Zeff value in AUG. These values are to be benchmarked against the Zeff values obtained by directly measuring the impurity densities in the plasma and are to be incorporated into standard analysis routines used at AUG.

Contact: Dr. Athina Kappatou

geeignet als
  • Masterarbeit Kern-, Teilchen- und Astrophysik
  • Masterarbeit Applied and Engineering Physics
Themensteller(in): Ulrich Stroth
Investigation of the detached divertor operation at the ASDEX Upgrade tokamak

The operation of future fusion reactors requires a significant reduction of the power flux from the hot plasma to the material components in the divertor. In a tokamak the magnetically confined plasma is separated from the region of plasma wall contact. With sufficient power dissipation, e.g. by atomic line radiation, the plasma in this region can be cooled down leading to a so-called detached condition, where the power flux to the wall is significantly reduced. In the thesis, the temporal behavior and stability of the detached state will be analyzed in order to understand its impact on the main plasma and plasma-wall interaction in future devices. Detachment will be characterized by analyzing experimental measurements and by comparison to simplified models. During the thesis one learns about divertor plasmas, various plasma diagnostics, and how to develop analysis tools for the interpretation of the experimental data.

Contact: Dr. Matthias Bernert

geeignet als
  • Masterarbeit Kern-, Teilchen- und Astrophysik
  • Masterarbeit Applied and Engineering Physics
Themensteller(in): Ulrich Stroth
Investigations into the physics of dipole magnetic field drift injection

The goal of the APEX/PAX group is the experimental study of magnetically confined electron/positron plasmas, which are predicted to exhibit highly atypical plasma physics properties (as compared to standard, electron/ion plasmas, in which the masses of the two species differ by more than three orders of magnitude). These ''pair plasmas'' have been the topic of a great deal of theoretical and computational work, and testing these predictions about them would significantly broaden our understanding of plasmas in general, but they have not yet been created in the laboratory. To accomplish this, our group is working on three interrelated challenges: A.) building the confinement device for the plasma, B.) getting enough positrons to ''fill'' the device, and C.) high-efficiency, highly-tuned transfer of positrons and electrons into the magnetic confiment region. This Master's project will focus on C. In a paper published last year, our group reported on the successful use of strategically applied electric fields, generating an ExB drift that moves positrons from the magnetic field of the beam line into the confinement region of a dipole magnet (Saitoh et al., New Journal of Physics 17, 103038 (2015)). More recently, we have improved the injection efficiency from 38% to >90%, using significantly different parameters. The goal of this master's project is an enhanced understanding of the physical mechanisms by which injection and subsequent behavior in the confinement region occur; these findings will essential for being able to reliably and predictably create the pair plasmas. The work will be done using both experimental and computational methods. Experiments will involve particle trajectory visualization using an electron gun and a background gas. Single-particle trajectory simuations will be performed and compared to the experimental results.

Contact: Dr. Eve Stenson

geeignet als
  • Masterarbeit Kern-, Teilchen- und Astrophysik
  • Masterarbeit Applied and Engineering Physics
Themensteller(in): Ulrich Stroth
Non-local turbulent plasma transport in fusion plasmas

The understanding of particle and energy transport in magnetically confined plasmas is one of the key topics in fusion research. In general both collisional and turbulent transport are described in terms of Fick’s law through a diffusion coefficient and a local temperature or density gradient. There exist observations, however, where transport at one location depends on the gradients at a different position. Such a non-local description would dramatically change our physical understanding of transport in fusion plasmas. In this thesis, turbulence measurements from different microwave diagnostics on the ASDEX Upgrade tokamak will be analyzed and changes in the fluctuation characteristics will be correlated with profile changes. The objective of the thesis is to search for non-local phenomena in the ASDEX Upgrade plasma.

Contact: Prof. Ulrich Stroth

geeignet als
  • Masterarbeit Kern-, Teilchen- und Astrophysik
  • Masterarbeit Applied and Engineering Physics
Themensteller(in): Ulrich Stroth
Phase velocities of turbulent fluctuations in the plasma edge

The turbulent phase velocity is the propagation velocity of turbulent fluctuations and is one of the main features to determine the underlying instability. Turbulence measurements by reflectometry on the ASDEX Upgrade tokamak yield rather small phase velocities compared to theoretical expectations. In this thesis a detailed survey of phase velocities is to be carried out based on turbulence simulations at different plasma parameters. To characterize the different turbulent regimes, different techniques to estimate the phase velocity are applied and results will be compared with experiment. The outcome of this thesis will help to experimentally identify different instabilities in the edge plasma of ASDEX Upgrade.

Contact: Dr. Peter Manz

geeignet als
  • Masterarbeit Kern-, Teilchen- und Astrophysik
  • Masterarbeit Applied and Engineering Physics
Themensteller(in): Ulrich Stroth
X-point Effect on Plasma Filament Dynamics

Turbulence in the region between the confined plasma and the material walls, called scape-off layer, is dominated by filamentary structures. The propagation of these structures is rather well understood in simple geometry. In diverted magnetic geometries like in the experiment ASDEX Upgrade a significant fraction of the exhaust power to the material surfaces is channeled through a point of null poloidal magnetic field called the X-point. In this work, the influence of the X-point on the dynamics of filamentary structures is studied with numerical simulations. Special emphasis is given to rarely studied regions of the diverted plasma as the high field side or the private flux region. This work is possible due to the recent development of a flux-coordinate independent code called GRILLIX.

Contact: Dr. Peter Manz

geeignet als
  • Masterarbeit Kern-, Teilchen- und Astrophysik
  • Masterarbeit Applied and Engineering Physics
Themensteller(in): Ulrich Stroth

Kondensierte Materie

Wenn Atome sich zusammen tun, wird es interessant: Grundlagenforschung an Festkörperelementen, Nanostrukturen und neuen Materialien mit überraschenden Eigenschaften treffen auf innovative Anwendungen.

Kern-, Teilchen-, Astrophysik

Ziel der Forschung ist das Verständnis unserer Welt auf subatomarem Niveau, von den Atomkernen im Zentrum der Atome bis hin zu den elementarsten Bausteinen unserer Welt.

Biophysik

Biologische Systeme, vom Protein bis hin zu lebenden Zellen und deren Verbänden, gehorchen physikalischen Prinzipien. Unser Forschungsbereich Biophysik ist deutschlandweit einer der größten Zusammenschlüsse in diesem Bereich.