Bachelor- and master theses

The scope of the topics can be adjusted. Feel free to contact us.

For the 2D version of the code, we want to improve the numerical dispersion while reducing the necessary spatial resolution. The code solves the two Maxwell curl equations and the plasma electron equation of motion. It is used for electromagnetic waves in fusion relevant plasmas with optional background magentic fields.

Two techniques are possible:

• Hexagonal grid: finite difference time domain (FDTD) scheme exists for vacuum, need to add plasma effects, UPML absorbing boudary conditions
• 4^th order methods: central differences in time and space AND coupling to plasma, simultaneous 4^th order (simultaneous may not be possible). There is already previous work on this topic.

Reflectometry is an active diagnostic that sends microwaves and millimeter waves into the plasma, which are then reflected at the location where the density becomes larger than the cutoff density. The reflected signal carries information about the plasma density, density fluctuations, and plasma flow.

In PCR:

• Microwave beam is sent to plasma with several receiving antennas
• Each receiving antenna defines different beam geometry, probing a different poloidal position
• Correlation of signals from different positions yields poloidal rotation direction or the pitch angle of magnetic field lines
• Turbulence from codes can be used as input for realistic scenarios

You can  build on previous work in this topic.

• Mitre-bends are the typical waveguide components for highly oversized waveguides because they are more compact than continuous bends
• For moderately oversized waveguides, diffraction effects can partly be compensated with quasi-optical designs
• Quasi-optical mitre-bends can accurately be calculated with PROFUSION.
• The work consists of parameter studies for different ratios of wavelength and waveguide diameter and the investigation of the broadband performance.

Multimegawatt transmission lines of millimeterwaves need diagnostics to ensure the proper alignment of the transmitted beams, since the transmission lines have to be oversized, and thus allow the propagation of unwanted modes.

The directional couplers are using small coupling holes (diameter < λ/2) in a mirror to sample the main beam on the mirror. We use the 3D fullwave code IPF-FD3D to simulate the coupling, in order to find optimal geometries.

Circular corrugated waveguides are used to transmit megawatts of millimeterwaves for ECHR. We use the 3D fullwave code IPF-FD3D to simulate the propagation in such oversized waveguides (diameter >> λ). The sub-wavelength size of the corrugation structure makes simulations challenging.

When comparing the wall currents of the HE11 mode in corrugated waveguides with the propagation of the TE11 mode in smooth waveguides, we cross check and cross calibrate the simulation results with theory.