Thesis topics

Our group is involved in the microwave technology for heating and diagnostics of the high temperature plasmas in the fusion experiments ASDEX Upgrade, Wendelstein 7-X, and TJ-K. The focus is on the design of advanced components and simulations of the propagation of microwaves in components and plasmas. We have developed several simulation codes for these applications.

Design of a 20 kW calorimetric dummy load for a 28 GHz heating system

  • 28 GHz gyrotron installation for TJ-K needs high power dummy load for testing and conditioning
  • Adapt existing design of cylindrical box with water-filled teflon hoses to this frequency
  • Build and test design

New Solvers for the fullwave reflectometry code IPF-FD3D

  • For the 2D version
  • Hexagonal grid: finite difference time domain (FDTD) scheme exists for vacuum, need to add plasma effects, UPML absorbing boudary conditions
  • 4th order methods: central differences in time and space AND coupling to plasma, simultaneous 4th order (simultaneous may not be possible)

Numerical investigation of poloidal correlation reflectometry

  • Microwave beam 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

3D Simulation of the ASDEX Upgrade Interferometer for the ICRF Launcher

  • 3D plasma simulation with IPF-FD3D
  • Interferometer beam with large transverse plasma density gradient
  • Interferometer frequency near density cutoff
  • Need for optimisation of sending and receiving antennas

Investigations for quasi-optical mitre bends

  • 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.

Investigations of the imaging characteristics of waveguides with a non-trivial cross-section

  • Rectangular waveguides have imaging properties, which allow the design of remote steering antennas for the heating of fusion plasmas
  • The angular range is, however, limited to about +/- 12°.
  • By choosing a slightly deformed waveguide cross-section, the dispersion relation of the modes can be changed, leading to a possibly enlarged steering range.
  • An eigenmode solver for deformed cross sections is already available and can be used for parameters studies.
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