Development of a high CMRR magnetic probe for the biased plasma in TU-Heliac

Satoshi Koike; Sumio Kitajima; Atsushi Okamoto; Keiichi Ishii; Yu Sato; Jo Tachibana; Toshihiro Oku; Kosuke Shimizu; Shigeru Inagaki; Yasuhiro Suzuki; Hiromi Takahashi; Masakazu Takayama

doi:10.1585/pfr.9.1202053

Development of a high CMRR magnetic probe for the biased plasma in TU-Heliac

Satoshi Koike, Sumio Kitajima, Atsushi Okamoto, Keiichi Ishii, Yu Sato, Jo Tachibana, Toshihiro Oku, Kosuke Shimizu, Shigeru Inagaki, Yasuhiro Suzuki, Hiromi Takahashi, Masakazu Takayama

Division of Nuclear Fusion Dynamics

Research output: Contribution to journal › Article

Abstract

The plasma in Tohoku University Heliac (TU-Heliac) is biased by a hot cathode that drives the J × B poloidal rotation. In the biased plasma, a density collapse accompanied by high-frequency bursting density and potential fluctuations was observed. To eliminate the effect of potential fluctuations and to measure the magnetic fluctuation, a high common mode rejection ratio (CMRR) magnetic probe with a preamplifier at the probe head in a vacuum vessel was designed and installed. Owing to the absolute calibration, the magnetic probe has a high magnetic sensitivity of 10⁴ V/T (@100 kHz), high CMRR of -75 dB (@500 kHz), and frequency bandwidth DC -1MHz. In the biased plasma, the power spectrum of the normal mode signal was 10⁴ times larger than that of the common mode signal in all frequency ranges, which indicates that the probe can successfully minimize the capacitive pickup noise relative to the actual magnetic fluctuation signal. In addition, we successfully observed the broad spectrum (100 kHz < f < 300 kHz) of the magnetic fluctuation and MHD instability in the biased plasma in TU-Heliac.

Original language	English
Article number	1202053
Journal	Plasma and Fusion Research
Volume	9
DOIs	https://doi.org/10.1585/pfr.9.1202053
Publication status	Published - 2014

All Science Journal Classification (ASJC) codes

Condensed Matter Physics

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Koike, S., Kitajima, S., Okamoto, A., Ishii, K., Sato, Y., Tachibana, J., Oku, T., Shimizu, K., Inagaki, S., Suzuki, Y., Takahashi, H., & Takayama, M. (2014). Development of a high CMRR magnetic probe for the biased plasma in TU-Heliac. Plasma and Fusion Research, 9, [1202053]. https://doi.org/10.1585/pfr.9.1202053

Development of a high CMRR magnetic probe for the biased plasma in TU-Heliac. / Koike, Satoshi; Kitajima, Sumio; Okamoto, Atsushi; Ishii, Keiichi; Sato, Yu; Tachibana, Jo; Oku, Toshihiro; Shimizu, Kosuke; Inagaki, Shigeru; Suzuki, Yasuhiro; Takahashi, Hiromi; Takayama, Masakazu.

In: Plasma and Fusion Research, Vol. 9, 1202053, 2014.

Research output: Contribution to journal › Article

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abstract = "The plasma in Tohoku University Heliac (TU-Heliac) is biased by a hot cathode that drives the J × B poloidal rotation. In the biased plasma, a density collapse accompanied by high-frequency bursting density and potential fluctuations was observed. To eliminate the effect of potential fluctuations and to measure the magnetic fluctuation, a high common mode rejection ratio (CMRR) magnetic probe with a preamplifier at the probe head in a vacuum vessel was designed and installed. Owing to the absolute calibration, the magnetic probe has a high magnetic sensitivity of 104 V/T (@100 kHz), high CMRR of -75 dB (@500 kHz), and frequency bandwidth DC -1MHz. In the biased plasma, the power spectrum of the normal mode signal was 104 times larger than that of the common mode signal in all frequency ranges, which indicates that the probe can successfully minimize the capacitive pickup noise relative to the actual magnetic fluctuation signal. In addition, we successfully observed the broad spectrum (100 kHz < f < 300 kHz) of the magnetic fluctuation and MHD instability in the biased plasma in TU-Heliac.",

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AU - Sato, Yu

AU - Tachibana, Jo

AU - Oku, Toshihiro

AU - Shimizu, Kosuke

AU - Inagaki, Shigeru

AU - Suzuki, Yasuhiro

AU - Takahashi, Hiromi

AU - Takayama, Masakazu

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AB - The plasma in Tohoku University Heliac (TU-Heliac) is biased by a hot cathode that drives the J × B poloidal rotation. In the biased plasma, a density collapse accompanied by high-frequency bursting density and potential fluctuations was observed. To eliminate the effect of potential fluctuations and to measure the magnetic fluctuation, a high common mode rejection ratio (CMRR) magnetic probe with a preamplifier at the probe head in a vacuum vessel was designed and installed. Owing to the absolute calibration, the magnetic probe has a high magnetic sensitivity of 104 V/T (@100 kHz), high CMRR of -75 dB (@500 kHz), and frequency bandwidth DC -1MHz. In the biased plasma, the power spectrum of the normal mode signal was 104 times larger than that of the common mode signal in all frequency ranges, which indicates that the probe can successfully minimize the capacitive pickup noise relative to the actual magnetic fluctuation signal. In addition, we successfully observed the broad spectrum (100 kHz < f < 300 kHz) of the magnetic fluctuation and MHD instability in the biased plasma in TU-Heliac.

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