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Development of a Real-Time Power/Polarization Monitor using FPGA for Electron Cyclotron Resonance Heating on LHD

Ryohei MAKINO¹⁾, Shin KUBO^1,2), Kenya KOBAYAHI¹⁾, Sakuji KOBAYASHI²⁾, Takashi SHIMOZUMA²⁾, Yasuo YOSHIMURA²⁾, Hiroe IGAMI²⁾, Hiromi TAKAHASHI²⁾, Shinya OGASAWARA¹⁾ and Takashi MUTOH²⁾

1)

Department of Energy Engineering and Science, Nagoya University, Nagoya 464-8603, Japan

2)

National Institute for Fusion Science, 322-6 Oroshi-cho, Toki 509-5292, Japan

(Received 10 December 2013 / Accepted 5 February 2014 / Published 14 March 2014)

Abstract

For optimization of electron cyclotron resonance heating (ECRH), it is important to measure power and polarization states of injected millimeter-waves in real-time. Arbitrary polarization states of millimeter-waves are realized by two grating mirror polarizers set at miter-bends in the corrugated waveguide transmission system on the Large Helical Device (LHD). The polarization state of an injected millimeter-wave determines the mode excitation purity, and therefore the power absorption efficiency in plasmas. The real-time power/polarization monitor of the injected millimeter-wave is required for optimization and/or feedback control of ECRH. The real-time power/polarization monitor is under development to be installed on a miter-bend near the ECRH antenna on LHD. Amplitudes and phases of two orthogonal polarizations of injected millimeter-waves are measured to determine the power and polarization states of waves. In this paper, the design and performance test of the real-time power/polarization monitor are reported. Intensities and relative phase of two orthogonal polarizations are measured by a newly developed monitor with heterodyne interferometer and fast ADC (800 MHz) with FPGA. Hardware of the power/polarization monitor works as designed qualitatively.

Copyright (c) 2014 The Japan Society of Plasma Science and Nuclear Fusion Research

Keywords

power/polarization monitor, millimeter-waves, electron cyclotron resonance heating, LHD, miter-bend, FPGA

DOI: 10.1585/pfr.9.3405024

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References

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This paper may be cited as follows:

Ryohei MAKINO, Shin KUBO, Kenya KOBAYAHI, Sakuji KOBAYASHI, Takashi SHIMOZUMA, Yasuo YOSHIMURA, Hiroe IGAMI, Hiromi TAKAHASHI, Shinya OGASAWARA and Takashi MUTOH, Plasma Fusion Res. 9, 3405024 (2014).