On velocity space interrogation regions of fast-ion collective Thomson scattering at ITER

Mirko Salewski, Stefan Kragh Nielsen, Henrik Bindslev, Vedran Furtula, N.N. Gorelenkov, Søren Bang Korsholm, Frank Leipold, Fernando Meo, Poul Michelsen, Dmitry Moseev, Morten Stejner Pedersen

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    Abstract

    The collective Thomson scattering (CTS) diagnostic proposed for ITER is designed to measure projected 1D fast-ion velocity distribution functions at several spatial locations simultaneously. The frequency shift of scattered radiation and the scattering geometry place fast ions that caused the collective scattering in well-defined regions in velocity space, here dubbed interrogation regions. Since the CTS instrument measures entire spectra of scattered radiation, many different interrogation regions are probed simultaneously. We here give analytic expressions for weight functions describing the interrogation regions, and we show typical interrogation regions of the proposed ITER CTS system. The backscattering system with receivers on the low-field side is sensitive to fast ions with pitch |p| = |v/v| <0.5–0.9 depending on the ion energy and the frequency shift of the scattered radiation. A forward scattering system with receivers on the high-field side would be sensitive to co- and counter-passing fast ions in narrow interrogation regions with pitch |p| > 0.6–0.8. Additionally, we use weight functions to reconstruct 2D fast-ion distribution functions, given two projected 1D velocity distribution functions from simulated simultaneous measurements with the back- and forward scattering systems.
    Original languageEnglish
    JournalNuclear Fusion
    Volume51
    Issue number8
    Pages (from-to)083014
    ISSN0029-5515
    DOIs
    Publication statusPublished - 2011

    Bibliographical note

    'This is an author-created, un-copyedited version of an article accepted for publication in Nuclear Fusion. IOP Publishing Ltd is not responsible for any errors or omissions in this version of the manuscript or any version derived from it. The definitive publisher-authenticated version is available online at 10.1088/0029-5515/51/8/083014

    Keywords

    • Fusion energy

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