Thesis Topics

Available Bachelor and Master thesis topics in the group Plasma Dynamics and Diagnostics

Thesis Topics

  1. (PhD) Development of a helicon plasma cell for particle-driven wakefield accelerators

    Plasma wakefield accelerators provide electric field gradients several orders of magnitude higher than conventional linear particle accelerators significantly reducing their size, thereby promising affordable and compact accelerators for various applications. High electric fields require high plasma densities. Helicon discharges are known to provide the highest densities in linear geometry. Numerical studies of the physics of helicon discharges to understand wave propagation and dissipation will go hand in hand with experimental studies at the University of Greifswald and the University of Wisconsin-Madison.
    An existing numerical code will be used and adapted where necessary and compared with commercial code packages. The experiments will be carried out in the frame of another Ph.D. project. The two projects are closely connected and the candidates are expected to regularly interact with each other, both online and in-person.


  2. (PhD) Interaction of shear flows and turbulent transport

    Within the framework of fundamental studies on self-organization processes in magnetized plasmas, various turbulent transport processes, which on the one hand drive the particle transport across the magnetic field and on the other hand can reduce it, are related to each other. Both types of processes are presumably in competition. This work sheds light on the detailed dependence of turbulent particle transport on shear flows – either self-excited through momentum transport or imposed by external control – and provides the basis for the under-standing of improved magnetic plasma confinement, which is of particular importance for hot fusion plasmas. For this purpose, the IGVP operates its own plasma confinement experiment TJ-K at the University of Stuttgart.
    The thesis involves experimental work in combination with the application of sophisticated data analysis methods in plasma turbulence.


  3. (BSc/MSc) Measurement of electron-temperature dynamics in TJ-K plasmas

    Turbulent heat transport in magnetized plasmas is co-determined by temperature fluctuations. In order to quantitatively record the dynamics in the electron temperature, a triple probe diagnostics is to be set up and tested. The evaluation for temperature fluctuations is carried out according to the literature. The measured time series are examined for statistical or turbulent properties. Of particular interest is the correlation between fluctuations in temperature and density. This is analyzed depending on the radial position.


  4. (BSc/MSc) OML extension for analyses of probe characteristics

    Previous evaluations of the probe characteristics at TJ-K are based on the theory of ideal probes. This way, a robust estimate of the electron temperature is possible, but absolute values ​​of the plasma density are too vague due to non-saturating currents at high probe bias. An improvement could be achieved by utilizing the so-called OML theory. This is to be tested for TJ-K plasmas. Density measurements from interferometry are used for comparison.


  5. (BSc/MSc) Power distribution over turbulence scales

    In turbulent flows, the power in the turbulent fluctuations follows a typical spectral distribution. In order to determine a wavenumber spectrum (k-spectrum), extensive simultaneous measurements of the fluctuating variables are necessary. The so-called pseudo-k method allows the estimation of wavenumber spectra from simpler two-point measurements. Using plasma fluctuation measurements with multi-probe arrays at TJ-K, pseudo-k spectra are examined for comparability with real wavenumber spectra.


  6. (BSc/MSc) PIC simulation of electrostatic waves in TJ-K plasmas

    A variety of waves exist in a plasma. This work deals with electrostatic and electromagnetic waves in a plasma and how they can be coupled. The free PIC code EPOCH is meant to be used for these investigations. For this purpose, it is necessary to make adjustments to the input parameters of the program such that it represents the plasma in the TJ-K stellarator. Furthermore, the propagation of electrostatic waves over a wide range of plasma parameters (magnetic field, heating power, plasma density) will be studied.


  7. (BSc oder MSc) Effect of plasma density fluctuations on wave coupling

    Plasma density fluctuations can deflect a microwave beam injected into a plasma and on average lead to a broadening of the beam. The effect on the coupling processes of electromagnetic with electrostatic waves is to be quantified with a code available at the institute. Thereby, the fluctuation amplitude, its spatial localization as well as the correlation length (average structure size) shall be varied. Finally, the results are to be transferred to existing experiments in order to estimate the degradation of the coupling efficiency there.


Mirko Ramisch

Dr.

Head of Plasma Dynamics and Diagnostics / Library officer

This image shows Alf Köhn-Seemann

Alf Köhn-Seemann

Dr.

Research associate, Plasma Dynamics and Diagnostics

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