Local measurements of correlated momentum and heat transport in the TFTR tokamak

Scott, S. D.; Diamond, P. H.; Fonck, R. J.; Goldston, Robert James; Howell, Robert B.; Jaehnig, Kurt P.; Schilling, G.; Synakowski, E.J.; Zarnstorff, M. C.; Bush, C. E.; Fredrickson, E. D.; Hill, K. W.; Janos, A.; Mansfield, D. K.; Owens, D. K.; Park, H.; Pautasso, G.; Ramsey, A. T.; Schivell, J.; Tait, G. D.; Tang, W. M.; Taylor, G.

doi:10.1103/physrevlett.64.531

Cited by 176 publications

(76 citation statements)

References 20 publications

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“…The link between momentum transport and ion heat transport has been observed on various machines and is well documented in the literature [8][9][10][11][12][13][14][15][16][17]94]. This link is often expressed in an effective Prandtl number Pr eff = χ eff ϕ /χ i , in which the effective diffusivity is defined to be the ratio of momentum flux ( ϕ ) and the gradient of the angular rotation (nmR 2 ∇ ).…”

Section: Experimental Observationsmentioning

confidence: 94%

“…Early experimental observations on momentum transport [8][9][10][11][12][13][14][15][16][17] and theoretical investigations into anomalous transport [18] suggest a strong coupling of ion heat and momentum transport, with the diagonal transport coefficients being of similar magnitude. These experiments were performed using neutral beam heating (NBH) which exerts a large torque on the plasma, and the understanding was that without external momentum input, the plasma rotation would be negligible.…”

Section: Introductionmentioning

confidence: 99%

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Overview of toroidal momentum transport

Angioni²,

et al. 2011

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Toroidal momentum transport mechanisms are reviewed and put in a broader perspective. The generation of a finite momentum flux is closely related to the breaking of symmetry (parity) along the field. The symmetry argument allows for the systematic identification of possible transport mechanisms. Those that appear to lowest order in the normalized Larmor radius (the diagonal part, Coriolis pinch, E ×B shearing, particle flux, and up-down asymmetric equilibria) are reasonably well understood. At higher order, expected to be of importance in the plasma edge, the theory is still under development.

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Section: Experimental Observationsmentioning

confidence: 94%

Section: Introductionmentioning

confidence: 99%

Overview of toroidal momentum transport

Angioni²,

et al. 2011

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“…Experimentally, there is growing evidence that the ion temperature gradient ͑ITG͒-driven instability and its associated turbulence and transport have an active and important role in core tokamak transport. [2][3][4][5][6] Other potential sources of core transport include trapped electron modes, short wavelength modes, e.g., electron temperature gradient ͑ETG͒ driven, and magnetic fluctuations. Experimental efforts on these include work on trapped electron modes, 7 short wavelength fluctuations, 8,9 and internal magnetic fluctuations.…”

Section: Introductionmentioning

confidence: 99%

Comparison of turbulence measurements from DIII-D low-mode and high-performance plasmas to turbulence simulations and models

et al. 2002

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Measured turbulence characteristics (correlation lengths, spectra, etc.) in low-confinement (L-mode) and high-performance plasmas in the DIII-D tokamak [Luxon et al., Proceedings Plasma Physics and Controlled Nuclear Fusion Research 1986 (International Atomic Energy Agency, Vienna, 1987), Vol. I, p. 159] show many similarities with the characteristics determined from turbulence simulations. Radial correlation lengths Δr of density fluctuations from L-mode discharges are found to be numerically similar to the ion poloidal gyroradius ρθ,s, or 5–10 times the ion gyroradius ρs over the radial region 0.2<r/a<1.0. Comparison of these correlation lengths to ion temperature gradient gyrokinetic simulations (the UCLA-University of Alberta, Canada UCAN code [Sydora et al., Plasma Phys. Controlled Fusion 38, A281 (1996)]) shows that without zonal flows simulation values of Δr are very long, spanning much of the 65 cm minor radius. With zonal flows included, these decrease to near the measured values in both magnitude and radial behavior. In order to determine if Δr scaled as ρθ,s or 5–10 times ρs, an experiment was performed which modified ρθs while keeping other plasma parameters approximately fixed. It was found that the experimental Δr did not scale as ρθ,s, which was similar to low-resolution UCAN simulations. Finally, both experimental measurements and gyrokinetic simulations indicate a significant reduction in the radial correlation length from high-performance quiescent double barrier discharges, as compared to normal L-mode, consistent with reduced transport in these high-performance plasmas.

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“…Plasma rotation and the underlying toroidal angular momentum transport were intensively first studied because neutral beam injection (NBI) was the heating method of choice for tokamaks. Given the fact that unbalanced NBI naturally drives toroidal rotation, and along with the experimental observation that the ion momentum and thermal diffusivities were comparable (v / $ v i ), 2 toroidal momentum transport was thought to be diffusive and comparable to the ion heat transport. However, the discovery of the non-diffusive character of toroidal momentum transport in the JFT-2M tokamak 3 disrupted that overly simple understanding of the toroidal rotation.…”

Section: Introductionmentioning

confidence: 99%

“…The observed intrinsic axial flows in CSDX raise two questions: (1) what generates the intrinsic axial flow; (2) what determines the mean axial flow profile? Intrinsic toroidal flows are driven by the residual axial stress P Res rz , which requires spectral symmetry breaking.…”

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confidence: 99%

Dynamics of intrinsic axial flows in unsheared, uniform magnetic fields

Diamond

et al. 2016

Physics of Plasmas

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A simple model for the generation and amplification of intrinsic axial flow in a linear device, controlled shear decorrelation experiment, is proposed. This model proposes and builds upon a novel dynamical symmetry breaking mechanism, using a simple theory of drift wave turbulence in the presence of axial flow shear. This mechanism does not require complex magnetic field structure, such as shear, and thus is also applicable to intrinsic rotation generation in tokamaks at weak or zero magnetic shear, as well as to linear devices. This mechanism is essentially the self-amplification of the mean axial flow profile, i.e., a modulational instability. Hence, the flow development is a form of negative viscosity phenomenon. Unlike conventional mechanisms where the residual stress produces an intrinsic torque, in this dynamical symmetry breaking scheme, the residual stress induces a negative increment to the ambient turbulent viscosity. The axial flow shear is then amplified by this negative viscosity increment. The resulting mean axial flow profile is calculated and discussed by analogy with the problem of turbulent pipe flow. For tokamaks, the negative viscosity is not needed to generate intrinsic rotation. However, toroidal rotation profile gradient is enhanced by the negative increment in turbulent viscosity.

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Local measurements of correlated momentum and heat transport in the TFTR tokamak

Cited by 176 publications

References 20 publications

Overview of toroidal momentum transport

Overview of toroidal momentum transport

Comparison of turbulence measurements from DIII-D low-mode and high-performance plasmas to turbulence simulations and models

Dynamics of intrinsic axial flows in unsheared, uniform magnetic fields

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