[Table of Contents]

Plasma and Fusion Research

Volume 8, 2402027 (2013)

Regular Articles

Notch Filter in 70 GHz Range for Microwave Plasma Diagnostics
Masaki NISHIURA, Shin KUBO, Kenji TANAKA, Sakuji KOBAYASHI, Kohta OKADA, Teruki NISHIMURA, Koji OKADA, Hiroshi KASAHARA, Shinya OGASAWARA1), Takashi SHIMOZUMA, Takashi MUTOH, Kazuo KAWAHATA, Teruo SAITO2), Yoshinori TATEMATSU2) and LHD experiment group
National Institute for Fusion Science, 322-6 Oroshi-cho, Toki 509-5292, Japan
1)
Nagoya University, Furo-cho, Chikusa-ku, Nagoya 464-8601, Japan
2)
FIR FU, University of Fukui, 3-9-1 Bunkyo, Fukui 910-8507, Japan
(Received 7 December 2012 / Accepted 1 March 2013 / Published 19 June 2013)

Abstract

A notch filter for the rejection of stray light from gigahertz range heating sources was developed to protect a vulnerable microwave plasma diagnostic system. As one of the applications, we consider the installation of the notch filter into the receiver of a collective Thomson scattering diagnostic in the Large Helical Device. Experimental observations indicate that two types of notch filters are required for main and spurious mode rejection; they have very narrow, steep shapes to avoid disturbing the diagnostic signal. On the basis of numerically simulated results, notch filters were fabricated, and their performance was evaluated. An attenuation level of 35 dB at 74.746 GHz with a 3 dB bandwidth of 0.49 GHz is achieved by two pairs of resonator cavities. This attenuation is acceptable in our study.

Keywords

millimeter wave filters, electron cyclotron emission, reflectometer, collective Thomson scattering, millimeter plasma diagnostics

DOI: 10.1585/pfr.8.2402027

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This paper may be cited as follows:

Masaki NISHIURA, Shin KUBO, Kenji TANAKA, Sakuji KOBAYASHI, Kohta OKADA, Teruki NISHIMURA, Koji OKADA, Hiroshi KASAHARA, Shinya OGASAWARA, Takashi SHIMOZUMA, Takashi MUTOH, Kazuo KAWAHATA, Teruo SAITO, Yoshinori TATEMATSU and LHD experiment group, Plasma Fusion Res. 8, 2402027 (2013).