Modelling of the ICRF induced E x B convection in the scrape-off-layer of ASDEX Upgrade

In magnetic controlled fusion devices, plasma heating with radio-frequency (RF) waves in the ion cyclotron (IC) range of frequency relies on the electric field of the fast wave to heat the plasma. However, the slow wave can be generated parasitically. The electric field of the slow wave can induce large biased plasma potential (DC potential) through sheath rectification. The rapid variation of the rectified potential across the equilibrium magnetic field can cause significant convective transport (E x B drifts) in the scrape-off layer (SOL). In order to understand this phenomenon and reproduce the experiments, 3D realistic simulations are carried out with the 3D edge plasma fluid and kinetic neutral code EMC3-Eirene in ASDEX Upgrade. For this, we have added the prescribed drift terms to the EMC3 equations and verified the 3D code results against the analytical ones in cylindrical geometry. The edge plasma potential derived from the experiments is used to calculate the drift velocities, which are then treated as input fields in the code to obtain the final density distributions. Our simulation results are in good agreement with the experiments

Millimetre Wave Power Measurement

There is currently no traceable power sensor for millimetre wave frequencies above 110 GHz. This thesis investigates a novel approach to remove this limitation by combining the placement of a uniquely designed microchip directly in waveguide. The design of the chip is novel in that it does not rely on a supporting structure or an external antenna when placed in the waveguide. The performance of the design was primarily analysed by computer simulation and verified with the measurement of a scale model. The results show that it is feasible to measure high frequency power by placing a chip directly in waveguide. It is predicted that the chip is able to absorb approximately 60% of incident power. Any further efficiency would require modification of the chip substrate. However, this proposed design should allow the standards institutes a reference that will enable the calibration of equipment to beyond 110 GHz