Experimental investigation of ion-temperature-gradient-like turbulence characteristics in T-10 core plasmas with toroidal and poloidal correlation reflectometry

Vershkov, V.A.; Soldatov, S.; Shelukhin, D. A.; Чистяков, В.В.

doi:10.1088/0029-5515/39/11y/318

Cited by 40 publications

(40 citation statements)

References 13 publications

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“…The decrease of the difference in α towards the core could be due to an increase in parallel correlation length according to equation 16. A parallel correlation length of 2 m would be rather small compared to result from previous studies [14,15,16,17](but not impossible).…”

Section: Comparison With the Cliste Code At Augmentioning

confidence: 64%

Magnetic field pitch angle and perpendicular velocity measurements from multi-point time-delay estimation of poloidal correlation reflectometry

Prisiazhniuk

Krämer–Flecken

Happel

et al. 2017

Plasma Phys. Control. Fusion

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Abstract. In fusion machines turbulent eddies are expected to be aligned with the direction of the magnetic field lines and to propagate in the perpendicular direction. Time delay measurements of density fluctuations can be used for the calculation of magnetic field pitch angle α and perpendicular velocity v ⊥ profiles. The method is applied to poloidal correlation reflectometry installed at ASDEX Upgrade and TEXTOR, which measure density fluctuations from poloidally and toroidally separated antennas. Validation of the method is achieved by comparison of the perpendicular velocity (composed of the ExB drift and the phase velocity of turbulence v ⊥ = v E×B +v ph ), with Doppler reflectometry measurements, and with neoclassic fluid calculations. An important condition for the application of the method is the presence of turbulence with sufficiently long decorrelation time. It is shown that at the shear layer the decorrelation time is reduced, limiting the application of the method. The magnetic field pitch angle measured by this method shows the expected dependence on the magnetic field, plasma current and radial position. The profile of the pitch angle reproduces the expected shape and values. However, a comparison with the equilibrium reconstruction code cliste suggests an additional inclination of turbulent eddies at the pedestal position (2-3• ). This additional angle decreases towards core and at the edge.

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Section: Comparison With the Cliste Code At Augmentioning

confidence: 64%

Magnetic field pitch angle and perpendicular velocity measurements from multi-point time-delay estimation of poloidal correlation reflectometry

Prisiazhniuk

Krämer–Flecken

Happel

et al. 2017

Plasma Phys. Control. Fusion

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“…The core turbulence follows two distinct phases -an initial transient suppression triggered by either the transition in the magnetic configuration from limiter to X-point, or perhaps to an improved ohmic confinement phase [3]. Secondly, the turbulence remains suppressed by the prompt formation of an e-ITB with a non-monotonic q profile.…”

Section: Discussionmentioning

confidence: 99%

Turbulence behaviour during electron heated reversed shear discharges in JET

Conway

Hogeweij

Baar

et al. 2002

Plasma Phys. Control. Fusion

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Low-frequency/long-wavelength density turbulence is found to be reduced within the volume enclosed by an electron thermal internal transport barrier generated with lower hybrid microwave heating in the JET tokamak. The turbulence reduction coincides with a region (typically r/a < 0.4) of negative, or reversed magnetic shear s and reduced electron thermal diffusion χ e . In the tokamak edge region (r/a > 0.8), the turbulence amplitude is also reduced coinciding with large positive magnetic shear s > 1. Estimates of the core turbulence wavelengths (λ ⊥ > 0.1 m) are not in agreement with expectations from electron temperature gradient instabilities.

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“…. At Russian tokamak T-10 LRC experiments with correlation reflectometry were performed for the first time [7]. Correlation reflectometry has the advantage of probing the plasma up to the core and therefore obtains information from regions deep in the plasma, where different mechanisms are responsible for the origin of the turbulence.…”

Section: Introductionmentioning

confidence: 99%

Long-range correlation properties of quasi-coherent modes at TEXTOR

Krämer‐Flecken

Soldatov

et al. 2015

New J. Phys.

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The paper reports on the first measurements of long-range correlations along field lines in the center of ohmic plasmas at TEXTOR. The measurements are performed with correlation reflectometry. For the first time the poloidal, toroidal and radial extension of quasi-coherent modes are simultaneously investigated using correlation reflectometry at two poloidally and toroidally separated positions. The experiments also allow the local determination of the toroidal velocity from a combination of delay time estimation and safety factor measurements from the same instrument. The paper investigates whether turbulence and which kind of turbulence, with respect to the frequency range, is aligned along field lines and embedded on iso-density surfaces in ohmic plasmas. It especially addresses the question of the properties of coherent structures in the vicinity of the q = 1 surface by analyzing propagation times and coherence levels from short-and long-range correlations. The results are discussed within the context of quasi-coherent modes as observed at T-10, TEXTOR, Tore Supra and recently JET and which are linked to trapped electron modes. Furthermore, the experiment tries to investigate whether a treatment of turbulence in two dimensions is sufficient or if 3D geometry has to be used for the description of turbulence stimulated transport. This is of importance for the development of turbulence codes and simulations.

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Experimental investigation of ion-temperature-gradient-like turbulence characteristics in T-10 core plasmas with toroidal and poloidal correlation reflectometry

Cited by 40 publications

References 13 publications

Magnetic field pitch angle and perpendicular velocity measurements from multi-point time-delay estimation of poloidal correlation reflectometry

Magnetic field pitch angle and perpendicular velocity measurements from multi-point time-delay estimation of poloidal correlation reflectometry

Turbulence behaviour during electron heated reversed shear discharges in JET

Long-range correlation properties of quasi-coherent modes at TEXTOR

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