Resolving the bulk ion region of millimeter-wave collective Thomson scattering spectra at ASDEX Upgrade

Morten Stejner Pedersen, Stefan Kragh Nielsen, Asger Schou Jacobsen, Søren Bang Korsholm, Frank Leipold, Fernando Meo, Poul Michelsen, Dmitry Moseev, Jesper Rasmussen, Mirko Salewski, M. Schubert, J. Stober, D. H. Wagner

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Abstract

Collective Thomson scattering (CTS) measurements provide information about the composition and velocity distribution of confined ion populations in fusion plasmas. The bulk ion part of the CTS spectrum is dominated by scattering off fluctuations driven by the motion of thermalized ion populations. It thus contains information about the ion temperature, rotation velocity, and plasma composition. To resolve the bulk ion region and access this information, we installed a fast acquisition system capable of sampling rates up to 12.5 GS/s in the CTS system at ASDEX Upgrade. CTS spectra with frequency resolution in the range of 1 MHz are then obtained through direct digitization and Fourier analysis of the CTS signal. We here describe the design, calibration, and operation of the fast receiver system and give examples of measured bulk ion CTS spectra showing the effects of changing ion temperature, rotation velocity, and plasma composition.
Original languageEnglish
JournalReview of Scientific Instruments
Volume85
Issue number9
Pages (from-to)093504
Number of pages12
ISSN0034-6748
DOIs
Publication statusPublished - 2014

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