Dresden 2017 – scientific programme

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MA: Fachverband Magnetismus

MA 24: Focus: Microwave and THz Properties, Developments and Applications of Dielectric Materials

MA 24.5: Talk

Tuesday, March 21, 2017, 11:40–12:00, GER 37

THz Diagnostics for fusion - A new challenge for dielectric windows — •Francesco Mazzocchi, Giovanni Grossetti, Dirk Strauss, and Theo Scherer — Karlsruhe Institüt für Technologie, Hermann Von Helmholtz Platz 1, 76344, Eggenstein Leopoldshafen

Polarimetry is a reliable methodology to estimate fundamental plasma parameters such as electronic density and poloidal field from the measure of the Faraday rotation angle. In this work we present a conceptual study of an innovative polarimetric system. The device foresees multiple lines of sight, so that the estimation of the aforementioned parameters can be performed at different cords. Dielectric windows play a fundamental role in this case, given the number beamlines that require access to the vacuum vessel. In order to have an appreciable Faraday rotation, sources in the range of the low THz are needed. Quantum Cascade Lasers represent a very promising solution but to work at low frequency (around 1.6 THz) they require cryogenic temperatures. The power output of such devices is still several order of magnitudes below the level guaranteed by the more common laser sources employed so far, such as DCN gas lasers. Therefore a strong focus on the production and characterization of ultra low loss dielectric materials (e.g. diamond, sapphire) for the cryostat and torus windows in the THz range is mandatory, to ensure the polarimeter probe beam absorption to be negligible and the device to work correctly.