A study of low-frequency microturbulence by CO2-laser collective scattering in the FT-2 tokamak

Bulanin, V. V.; Vers, A. V.; Esipov, L. A.; Its, E. R.; Петров, А. В.; Roitershtein, V. S.

doi:10.1134/1.1354220

Cited by 2 publications

(4 citation statements)

References 9 publications

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“…Again, the same conclusion was reached in Ref. 19 and is thought to indicate that ''the character of motion is different for fluctuations with different scale lengths.'' We found that the autopower slope versus frequency was steepest for H-mode phases, and that the L-and H-mode spectral shapes were close to identical if the H-mode frequencies were scaled by a factor 1.8.…”

Section: A W7-as Measurementssupporting

confidence: 73%

“…III B͒. We note that this spectral shape has been observed in the FT-2 tokamak as well 19 ͑for k Ќ у14 cm Ϫ1 ͒, whereas pronounced ''double hump'' spectra peaking away from DC as observed in Tore Supra ͑see, e.g., Ref. 37͒ have not been observed in W7-AS, even with good spatial resolution.…”

Section: A W7-as Measurementsmentioning

confidence: 52%

“…In the experiments analyzed herein the direction of k Ќ was set along the major radius R of the stellarator. Heterodyne detection is performed, meaning that we can distinguish the direction of the fluctuations as being due to inward ͑outward͒ ͓positive ͑negative͒ frequencies͔ traveling fluctuations parallel to R. The wavenumber can be varied from 14 to 62 cm Ϫ1 , which are extremely large values compared to similar diagnostics, [17][18][19] but comparable to those of Ref. 20.…”

Section: B the Lotus Diagnosticmentioning

confidence: 99%

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Low- and high-mode separation of short wavelength turbulence in dithering Wendelstein 7-AS plasmas

Basse¹,

Zoletnik²,

Saffman³

et al. 2002

Physics of Plasmas

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In this article measurements of small scale electron density fluctuations in dithering high confinement ͑H͒-mode plasmas obtained by collective scattering of infrared light are presented. A scan of the fluctuation wavenumber was made in a series of similar discharges in the Wendelstein 7-AS ͑W7-AS͒ stellarator ͓H. Renner et al., Plasma Phys. Control. Fusion 31, 1579 ͑1989͔͒. The experimental setup and discharge properties are described. H ␣-light observing an inner limiter was used to separate low confinement ͑L͒and H-mode phases of the plasma; the separated density fluctuations are characterized. It was found that L-͑H-͒ mode fluctuations dominate at high ͑low͒ frequencies, respectively, and that they possess well-defined and distinguishable scaling properties. Wavenumber spectra for Land H-mode measurements are calculated and fitted by power-laws and exponential functions. The separated measurements can be fitted with the same exponents in Land H-mode. Correlations between the density fluctuations, the H ␣-signal and magnetic fluctuations as measured by Mirnov coils were analyzed. Correlation calculations using 50 ms time windows ͑several dithering periods͒ with time lag steps of 100 s showed that all the fluctuating quantities are highly correlated and that the maximum correlation occurs for high frequency density fluctuations. Performing separate Land H-mode correlations on a 20 s time scale between magnetic and density fluctuations leads to the result that the minimum correlation time scale in L-mode is of order 100 s, while no correlation exists for H-mode.

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Section: A W7-as Measurementssupporting

confidence: 73%

Section: A W7-as Measurementsmentioning

confidence: 52%

Section: B the Lotus Diagnosticmentioning

confidence: 99%

See 1 more Smart Citation

Low- and high-mode separation of short wavelength turbulence in dithering Wendelstein 7-AS plasmas

Basse¹,

Zoletnik²,

Saffman³

et al. 2002

Physics of Plasmas

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show abstract

“…Subsequently, detection of density fluctuations using lasers has been performed in numerous machines, both applying the technique used in the ATC tokamak [12][13][14][15][16][17] and related methods, e.g. far-infrared (FIR) scattering [18][19][20] and phase-contrast imaging (PCI).…”

mentioning

confidence: 99%

Small-angle Scattering Theory Revisited: Photocurrent and Spatial Localization

Basse

Zoletnik

Michelsen³

2005

Phys. Scr.

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In this paper theory on collective scattering measurements of electron density fluctuations in fusion plasmas is revisited. We present the first full derivation of the expression for the photocurrent beginning at the basic scattering concepts. Thereafter we derive detailed expressions for the auto- and crosspower spectra obtained from measurements. These are discussed and simple simulations made to elucidate the physical meaning of the findings. In this context, the known methods of obtaining spatial localization are discussed and appraised. Where actual numbers are applied, we utilize quantities from two collective scattering instruments The ALTAIR diagnostic on the Tore Supra tokamak [A Truc et al, "ALTAIR An infrared laser scattering diagnostic on the Tore Supra tokamak", Rev. Sci. Instrum. 63 3716–3724 (1992)] and the LOTUS diagnostic on the Wendelstein 7-AS stellarator [M Saffman et al, "CO2 laser based two-volume collective scattering instrument for spatially localized turbulence measurements", Rev. Sci. Instrum. 72 2579–2592 (2001)].

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A study of low-frequency microturbulence by CO2-laser collective scattering in the FT-2 tokamak

Cited by 2 publications

References 9 publications

Low- and high-mode separation of short wavelength turbulence in dithering Wendelstein 7-AS plasmas

Low- and high-mode separation of short wavelength turbulence in dithering Wendelstein 7-AS plasmas

Small-angle Scattering Theory Revisited: Photocurrent and Spatial Localization

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