Plasma and Fusion Research

Volume 3, 044 (2008)

Regular Articles

Experimental Study of Drift Wave Turbulence in Linear Plasmas

Takuma YAMADA, Sanae -I. ITOH, Takashi MARUTA¹⁾, Naohiro KASUYA²⁾, Shunjiro SHINOHARA¹⁾, Yoshihiko NAGASHIMA, Masatoshi YAGI, Kenichiro TERASAKA¹⁾, Shigeru INAGAKI, Yoshinobu KAWAI, Masayuki FUKAO³⁾, Akihide FUJISAWA²⁾ and Kimitaka ITOH²⁾

Research Institute for Applied Mechanics, Kyushu University, Kasuga 816-8580, Japan
1): Interdisciplinary Graduate School of Engineering Sciences, Kyushu University, Kasuga 816-8580, Japan
2): National Institute for Fusion Science, Toki 509-5292, Japan
3): Myojocho, Uji 611-0014, Japan

(Received 1 December 2007 / Accepted 18 June 2008 / Published 10 July 2008)

Abstract

Linear plasmas allow multi-point, low-temperature measurements with Langmuir probes. We measured ion saturation-current fluctuations of a Large Mirror Device-Upgrade linear plasma using a poloidal Langmuir probe array. By varying the discharge conditions, the spatiotemporal behavior showed a change from a coherent sine wave to a turbulent waveform through a periodic, modulated sine wave. The two-dimensional (poloidal wave number and frequency) power spectrum for each regime showed a single fluctuation peak, a peak and its harmonics, and a number of peaks in the poloidal wave number-frequency space. Bi-spectral analysis was performed for the turbulent regime, and showed the existence of nonlinear couplings among fluctuation peaks and broadband components.

Keywords

linear plasma, drift wave, turbulence, broadband fluctuation, bi-spectral analysis

DOI: 10.1585/pfr.3.044

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This paper may be cited as follows:

Takuma YAMADA, Sanae -I. ITOH, Takashi MARUTA, Naohiro KASUYA, Shunjiro SHINOHARA, Yoshihiko NAGASHIMA, Masatoshi YAGI, Kenichiro TERASAKA, Shigeru INAGAKI, Yoshinobu KAWAI, Masayuki FUKAO, Akihide FUJISAWA and Kimitaka ITOH, Plasma Fusion Res. 3, 044 (2008).