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Santanu Banerjee,
H Zushi,
N Nishino,
Y Nagashima,
K Hanada,
M Ishiguro, T Ryoukai,
S Tashima,
T Inoue,
K Nakamura,
H Idei,
M Hasegawa,
A Fujisawa,
K Matsuoka
[show abstract]
[hide abstract]
ABSTRACT: A fast visible imaging system is installed on the spherical tokamak QUEST to study edge turbulence. The camera uses a complementary metal-oxide semiconductor detector with a maximum resolution of 1024 × 1024 at 7000 frames∕s (fps) and can achieve 775 kfps at a resolution of 128 × 24. In this paper, we present the salient features of the system and its application to study edge turbulence in 8.2 GHz ECRH driven slab plasma, without plasma current. Vertical magnetic field (B(z)) topology is varied with three sets of poloidal field (PF) coils and the variation in the edge turbulence is investigated as a function of the B(z) strength and curvature. Fluctuation amplitude was highest for the shallow PF well. Cross-correlation coefficient shows distinct coherent mode along z direction at the steep density gradient region and it grows with the PF mirror ratio.
The Review of scientific instruments 10/2012; 83(10):10E524. · 1.52 Impact Factor
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Santanu Banerjee,
H. Zushi,
N. Nishino,
Y. Nagashima,
K. Hanada,
M. Ishiguro, T. Ryoukai,
S. Tashima,
T. Inoue,
K. Nakamura,
H. Idei,
M. Hasegawa,
A. Fujisawa,
K. Matsuoka
[show abstract]
[hide abstract]
ABSTRACT: A fast visible imaging system is installed on the spherical tokamak QUEST to study edge turbulence. The
camera uses a complementary metal-oxide semiconductor detector with a maximum resolution of 1024×1024
at 7000 frames/s (fps) and can achieve 775 kfps at a resolution of 128×24. In this paper, we present the salient
features of the system and its application to study edge turbulence in 8.2 GHz ECRH driven slab plasma,
without plasma current. Vertical magnetic field (Bz) topology is varied with three sets of poloidal field (PF)
coils and the variation in the edge turbulence is investigated as a function of the Bz strength and curvature.
Fluctuation amplitude was highest for the shallow PF well. Cross-correlation coefficient shows distinct
coherent mode along z direction at the steep density gradient region and it grows with the PF mirror ratio.
Review of Scientific Instruments 01/2012; · 1.37 Impact Factor
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Santanu Banerjee,
H. Zushi,
N. Nishino,
K. Hanada,
H. Q. Liu,
M. Ishiguro, T. Ryoukai,
S. Tashima,
K. Nakamura,
H. Idei,
M. Hasegawa,
A. Fujisawa,
the QUEST group
[show abstract]
[hide abstract]
ABSTRACT: Edge turbulence has been imaged on QUEST at high
temporal resolution (50 kHz) using a fast framing visible camera.
Statistical features of fluctuations including blobs are investigated
in both open and closed magnetic configurations. Higher order
moments of fluctuations including blobs and their mutual relationships
are investigated. Close resemblance of the density pdf with
Gaussian or beta distributions has earlier been predicted. Hence,
an attempt has been made to characterize the density pdf with
respect to the Pearson system to ascertain the implications of the
stochastic forces.
IEEE Transactions on Plasma Science 01/2011; 39(11):3006. · 1.17 Impact Factor
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H. Zushi, T. Ryoukai,
K. Kikukawa,
T. Morisaki,
R. Bhattacharyay,
T. Yoshinaga,
K. Hanada,
T. Sakimura,
H. Idei,
K. Dono, [......],
K. Nagasaki,
M. Sakamoto,
Y. Nakashima,
Y. Higashizono,
K. N. Sato,
K. Nakamura,
M. Hasegawa,
S. Kawasaki,
H. Nakashima,
A. Higashijima
[show abstract]
[hide abstract]
ABSTRACT: Two-dimensional structure of density fluctuations is examined during the current jump phase, indicating a change from the open magnetic fields to the closed ones. During the smooth current ramp-up phase the two-dimensional contour of the LiI intensity shows vertically alignment, consistent with the magnetic surfaces. At the inflection point in Ip ramp-up the LiI intensity contour becomes flat in the observation regime and then suddenly a steep gradient and higher intensity regime are formed in the vertical direction. This higher intensity corresponds to a burst of LiI waveform. According to these changes in the contour, it is found that, within ±1 ms around the burst of LiI, a low frequency coherent wave with a long wavelength rapidly grows. The relations with other signals (magnetic flux and microwave stray power) are discussed with respect to the topological change in the magnetic configuration and mode conversion of the incident electromagnetic waves.
Plasma Science and Technology 08/2009; 11(4):397. · 0.41 Impact Factor
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