Real time polarization monitor developed for high power electron cyclotron resonance heating and current drive experiments in large helical device

T. Notake, H. Idei, S. Kubo, T. Shimozuma, Y. Yoshimura, S. Kobayashi, Y. Mizuno, S. Ito, Y. Takita, K. Ohkubo, W. Kasparek, T. Watari, R. Kumazawa

    Research output: Contribution to journalArticle

    12 Citations (Scopus)

    Abstract

    The polarization state of a wave is an important factor in electron cyclotron resonance heating (ECRH) and current drive (ECCD), for it strongly affects the propagation and absorption of the wave in the plasma. A real-time monitor of the polarization of the EC beam has been developed for use in ECRH/ECCD experiments in large helical device (LHD). Two orthogonal components of the wave field are measured in one of the miter-bends by use of a specially designed coupler and a waveguide circuit with a 0°-90° phase switch to deduce the polarization parameters: the polarization angle α and the ellipticity β. Since fast-response pin diodes are used for the switches, the polarization is determined every 3 ms, facilitating real time acquisition of the polarization. This article reports on the design and the principle of this monitor as well as on the algorithm used to calculate α and β. This article also reports on the method of calibration, for the accuracy of this measurement depends on it. Finally, a comparison is made between polarization parameters measured by a monitor actually installed on one of the ECRH transmission lines on LHD and the value set by the polarizer in ECRH experiments.

    Original languageEnglish
    Article number023504
    Pages (from-to)023504-1-023504-9
    JournalReview of Scientific Instruments
    Volume76
    Issue number2
    DOIs
    Publication statusPublished - Jan 25 2005

    All Science Journal Classification (ASJC) codes

    • Instrumentation

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  • Cite this

    Notake, T., Idei, H., Kubo, S., Shimozuma, T., Yoshimura, Y., Kobayashi, S., Mizuno, Y., Ito, S., Takita, Y., Ohkubo, K., Kasparek, W., Watari, T., & Kumazawa, R. (2005). Real time polarization monitor developed for high power electron cyclotron resonance heating and current drive experiments in large helical device. Review of Scientific Instruments, 76(2), 023504-1-023504-9. [023504]. https://doi.org/10.1063/1.1848657