Observation of a localized transition from edge to core density turbulence in the TFTR tokamak

Durst, R.; Fonck, R. J.; Kim, J. S.; Paul, S. F.; Bretz, N.; Bush, C. E.; Chang, Z.; Hülse, R.

doi:10.1103/physrevlett.71.3135

Cited by 50 publications

(39 citation statements)

References 14 publications

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“…Moreover, the dual-mode nature of the fluctuations ͑in LSN case only͒ is similar to observations on the Tokamak Fusion Test Reactor ͑TFTR͒, 21 where such double-mode propagation for the fluctuations was observed near the edge. 22 In contrast, however, the fluctuation propagation directions were different ͑perhaps due to different magnetic geometry; the TFTR plasma had a circular cross section and had a limiter͒. In the TFTR case, the higher frequency mode propagated in the electron diamagnetic direction, while the lower frequency mode propagated in the ion diamagnetic direction.…”

Section: -3mentioning

confidence: 99%

Effect of ion ∇B drift direction on density fluctuation poloidal flow and flow shear

et al. 2005

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The divertor magnetic geometry has a significant effect on the poloidal velocity and resulting velocity shear of turbulent density fluctuations in the outer region of L-mode tokamak plasmas, as determined via two-dimensional measurements of density fluctuations with beam emission spectroscopy on DIII-D ͓J. L. Luxon, Nucl. Fusion 42, 614 ͑2002͔͒. Plasmas with similar parameters, except that in one case the ion ١B drift points towards the divertor X point ͑lower-single-null, LSN͒, and in the other case, the ion ١B drift points away from the divertor X point ͑upper-single-null, USN͒, are compared. Inside r / a = 0.9, the turbulence characteristics ͑density fluctuation amplitude, flow direction, correlation lengths͒ are similar in both cases, while near r / a = 0.92, a dramatic reversal of the poloidal velocity of turbulent eddies relative to the core flow direction is observed in plasmas with the ion ١B drift pointing towards the divertor X point. No such velocity reversal is observed in plasmas with the ion ١B drift pointing away from the divertor X point. This poloidal velocity reversal results in a significantly larger local shear in the poloidal velocity of density fluctuations in plasmas with the ion ١B drift pointing towards the divertor X point. Additionally, these plasmas locally exhibit significant dispersion with two distinct and counterpropagating turbulence modes. Likewise, the radial correlation length of the density fluctuations is reduced in these plasmas, consistent with biorthogonal decomposition measurements of dominant turbulence structures. The naturally occurring density fluctuation poloidal velocity shear in these LSN plasmas may facilitate the L-H transition that occurs at an input power of roughly one-half to one-third that of corresponding plasmas with the ion ١B drift pointing away from the X point.

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Section: -3mentioning

confidence: 99%

Effect of ion ∇B drift direction on density fluctuation poloidal flow and flow shear

et al. 2005

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“…The measurement of large space fluctuations ( Ќ ϭ2 /k Ќ տ6 cm) are made using special techniques with diagnostic neutral beams, the heating neutral beams, and microwave reflectometry. The beam emission spectroscopy measurements of Durst et al (1993) show fluctuations at the level of ñ /nϳ0.01 in the range r/aϭ0.7 to 0.8 with a peak in the k spectrum at about 1 cm Ϫ1 . The reflectometry measurements of Mazzucato and Nazikian (1993), shown in Fig.…”

Section: J Long-wavelength Electron Drift Wavesmentioning

confidence: 99%

“…The fluctuation measurement at wave numbers k Ќ Շ1 cm Ϫ1 require the techniques of reflectometry (Doyle et al, 1991;Mazzucato and Nazikian, 1993) and the indirect method of beam emission spectroscopy as in the Durst et al (1993) experiment.…”

Section: Drift-wave Diffusivities and The Ion Inertial Scale Lengthmentioning

confidence: 99%

Drift waves and transport

1999

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Drift waves occur universally in magnetized plasmas producing the dominant mechanism for the transport of particles, energy and momentum across magnetic field lines. A wealth of information obtained from quasistationary laboratory experiments for plasma confinement is reviewed for drift waves driven unstable by density gradients, temperature gradients and trapped particle effects. The modern understanding of Bohm transport and the role of sheared flows and magnetic shear in reducing the transport to the gyro-Bohm rate are explained and illustrated with large scale computer simulations. The types of mixed wave and vortex turbulence spontaneously generated in nonuniform plasmas are derived with reduced magnetized fluid descriptions. The types of theoretical descriptions reviewed include weak turbulence theory, Kolmogorov anisotropic spectral indices, and the mixing length. A number of standard turbulent diffusivity formulas are given for the various space-time scales of the drift-wave turbulent mixing. [S0034-6861(99)00803-X] CONTENTS

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“…[5][6][7] Experimental evidence suggests that core plasma instabilities related to ion temperature gradient modes change into drifttype mode near the plasma edge. 8 It has also been suggested that the edge turbulence could have its origin in the plasma center, where the magnetic fluctuations have a fundamental role. 9 These facts suggest that the coupling between electrostatic turbulence and Alfvén waves are significant 10 and various models have been developed to study drift-Alfvén turbulence.…”

Section: Introductionmentioning

confidence: 99%

Nonmodal energetics of electromagnetic drift waves

2000

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The linear properties of an electromagnetic drift-wave model are examined. The linear system is non-normal in that its eigenvectors are not orthogonal with respect to the energy inner product. The non-normality of the linear evolution operator can lead to enhanced finite-time growth rates compared to modal growth rates. Previous work with an electrostatic drift-wave model found that nonmodal behavior is important in the hydrodynamic limit. Here, similar behavior is seen in the hydrodynamic regime even with the addition of magnetic fluctuations. However, unlike the results for the electrostatic drift-wave model, nonmodal behavior is also important in the adiabatic regime with moderate to strong magnetic fluctuations.

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Observation of a localized transition from edge to core density turbulence in the TFTR tokamak

Cited by 50 publications

References 14 publications

Effect of ion ∇B drift direction on density fluctuation poloidal flow and flow shear

Effect of ion ∇B drift direction on density fluctuation poloidal flow and flow shear

Drift waves and transport

Nonmodal energetics of electromagnetic drift waves

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