A progress report on recent experiments in the WEGA stellarator is given dedicated to diagnostic development -especially for the 0.5 T operation of 28 GHz ECR heated plasmas -and magnetic field line visualization experiments in the vacuum field. Furthermore, results from transport and turbulence studies in the plasma edge and first measurements inside magnetic islands are presented with the help of 1D and 2D Langmuir probe arrays. Additionally, the prototype installation of the Wendelstein 7-X control system is under continuous tests and further development at WEGA.
This paper gives an overview of recent results on the application of electron Bernstein waves for plasma heating and diagnostic purposes at the WEGA stellarator. By applying a two-step mode conversion process it was possible to reach over-dense argon and helium plasmas with central densities of above 0.97 × 10 19 m −3 at a magnetic field strength of 0.5 T fully sustained by electrostatic Bernstein waves. An unexpected feature observed during the experiments was the detection of a strong increase of the radiation temperature associated with the existence of a super-thermal electron component in the keV-range during this heating period.
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