05pE26P
揺動の2次元断面構造の推定法
Estimation of 2D cross-sectional structure of fluctuation
山田琢磨1,2, 稲垣滋2,3, 小林達哉4, 永島芳彦2,3, 満薗友宏4, 三輪祐大4, 藤野博充4,佐々木真2,3, 糟谷直宏2,3, Maxime Lesur2, 小菅佑輔3,5, 藤澤彰英2,3, 伊藤早苗2,3, 伊藤公孝2,6
Takuma Yamada1,2, Shigeru Inagaki2,3, Tatsuya Kobayashi4, Yoshihiko Nagashima2,3,Tomohiro Mitsuzono4, Yudai Miwa4, Hiromitsu Fujino4, Makoto Sasaki2,3, Naohiro Kasuya2,3,Maxime Lesur2, Yusuke Kosuga3,5, Akihide Fujisawa2,3, Sanae-I. Itoh2,3, Kimitaka Itoh2,6
九大基幹教育院1, 九大伊藤極限プラズマ研究セ2, 九大応力研3,九大総理工4, 九大高等院5, 核融合研6
ARTSCI, Kyushu Univ.1, Itoh Research Center, Kyushu Univ.2, RIAM Kyushu Univ.3,IGSES, Kyushu Univ.4, IAS Kyushu Univ.5, IAS Kyushu Univ.6
Study of meso-scale structures, such as streamersand zonal flows, has been an important subject forunderstanding anomalous transports in linear andtoroidal plasmas. Recently, a streamer structure wasfound in a linear cylindrical plasma, LMD-U [1]. Inaddition, a certain wave named ‘mediator’, whichhad the same frequency and poloidal wave number
as the envelope of the streamer structure, was foundto be strongly nonlinearly coupled with drift wave
turbulence and playing an important role for thestreamer formation.
In order to estimate the 2D cross-sectional
structures of the streamer structure and fluctuation,
a 64 channel poloidal probe array and a radiallymobile probe were used. As a set of referenceprobes, the poloidal probe array measured themediator mode. The phase structure of the mediator
was acquired by calculating the cross spectrum
between the radially mobile probe and reference. As
shown in Fig. 1, it had a phase node in the radialdirection. The bi-phase of the nonlinear coupling
between the streamer and mediator indicates thephase difference between the envelope of thestreamer and mediator. The streamer components
were measured with the radially mobile probe, andthe bi-phase between them and the mediatormeasured with the poloidal probe array showed aflat radial profile, indicating that the streamer
structure was radially elongated. These features
were quite equivalent with a pair of fast and slow
modes predicted by a nonlinear Schrödingerequation based on the Hasegawa-Mima model [2].
The fast and slow modes correspond to the streamer
structure and mediator, respectively. Such kind of astreamer structure, accompanied with a mediator,
was also observed in a nonlinear simulation of drift
waves in linear plasmas, using a three-field reduced
fluid model [3]. The Numerical Linear Device(NLD) code clearly presented the generation of thestreamer structure and clarified that the collision
frequency between ions and neutrals plays animportant role for the selection rule of generating
meso-scale structures including streamers [3].
On the other hand, study of controlling thestreamer was performed in the PANTA device bybiasing the end plate. During the end plate biasing,
the streamer was suppressed, the fluctuation level
was reduced, and the electron density profile
became more peaked. Changes in the 2D
cross-sectional structures of the streamer structureand fluctuation are also reported.
[1] T. Yamada et al., Nature Phys. 4, 721 (2008).
[2] T. Yamada et al., Phys. Rev. Lett. 105, 225002(2010).
[3] N. Kasuya et al., Phys. Plasmas 15, 052302 (2008).

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Fig. 1. 2D cross-sectional phase structure of themediator mode calculated from the real part of the crossspectrum between the radialy mobile probe and poloidal
probe array.