title: Resolving the bulk ion region of millimeter-wave collective Thomson scattering spectra at ASDEX Upgrade.
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.
authors.affiliation: Department of Physics, Association EURATOM-DTU, Technical University of Denmark, DK-2800 Kgs. Lyngby, Denmark.
authors.forename: M
authors.initials: M
authors.lastname: Stejner
authors.affiliation: Department of Physics, Association EURATOM-DTU, Technical University of Denmark, DK-2800 Kgs. Lyngby, Denmark.
authors.forename: S
authors.initials: S
authors.lastname: Nielsen
authors.affiliation: Department of Physics, Association EURATOM-DTU, Technical University of Denmark, DK-2800 Kgs. Lyngby, Denmark.
authors.forename: A S
authors.initials: AS
authors.lastname: Jacobsen
authors.affiliation: Department of Physics, Association EURATOM-DTU, Technical University of Denmark, DK-2800 Kgs. Lyngby, Denmark.
authors.forename: S B
authors.initials: SB
authors.lastname: Korsholm
authors.affiliation: Department of Physics, Association EURATOM-DTU, Technical University of Denmark, DK-2800 Kgs. Lyngby, Denmark.
authors.forename: F
authors.initials: F
authors.lastname: Leipold
authors.affiliation: Department of Physics, Association EURATOM-DTU, Technical University of Denmark, DK-2800 Kgs. Lyngby, Denmark.
authors.forename: F
authors.initials: F
authors.lastname: Meo
authors.affiliation: Department of Physics, Association EURATOM-DTU, Technical University of Denmark, DK-2800 Kgs. Lyngby, Denmark.
authors.forename: P K
authors.initials: PK
authors.lastname: Michelsen
authors.affiliation: Max-Planck-Institut für Plasmaphysik, EURATOM-Association, Boltzmannstr. 2, 85748 Garching, Germany.
authors.forename: D
authors.initials: D
authors.lastname: Moseev
authors.affiliation: Department of Physics, Association EURATOM-DTU, Technical University of Denmark, DK-2800 Kgs. Lyngby, Denmark.
authors.forename: J
authors.initials: J
authors.lastname: Rasmussen
authors.affiliation: Department of Physics, Association EURATOM-DTU, Technical University of Denmark, DK-2800 Kgs. Lyngby, Denmark.
authors.forename: M
authors.initials: M
authors.lastname: Salewski
authors.affiliation: Max-Planck-Institut für Plasmaphysik, EURATOM-Association, Boltzmannstr. 2, 85748 Garching, Germany.
authors.forename: M
authors.initials: M
authors.lastname: Schubert
authors.affiliation: Max-Planck-Institut für Plasmaphysik, EURATOM-Association, Boltzmannstr. 2, 85748 Garching, Germany.
authors.forename: J
authors.initials: J
authors.lastname: Stober
authors.affiliation: Max-Planck-Institut für Plasmaphysik, EURATOM-Association, Boltzmannstr. 2, 85748 Garching, Germany.
authors.forename: D H
authors.initials: DH
authors.lastname: Wagner