Electron transport and the critical temperature gradient

Horton, W.; Hoang, G. T.; Bourdelle, C.; Garbet, X.; Ottaviani, M.; Colas, L.

doi:10.1063/1.1690761

Cited by 42 publications

(45 citation statements)

References 36 publications

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“…HSX has very low magnetic shear, and this calculation is consistent with previous estimates of the critical gradient for ETG modes in a shearless slab, g e,c ¼ 2/3. 20 At left in Figure 10, the experimental temperature and density gradient scale lengths for the three heat pulse propagation experiments are described in Sec. II.…”

Section: Comparison To Gyrokinetic Calculationsmentioning

confidence: 99%

Profile stiffness measurements in the Helically Symmetric experiment and comparison to nonlinear gyrokinetic calculationsa)

et al. 2015

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Stiffness measurements are presented in the quasi-helically symmetric experiment (HSX), in which the neoclassical transport is comparable to that in a tokamak and turbulent transport dominates throughout the plasma. Electron cyclotron emission is used to measure the local electron temperature response to modulated electron cyclotron resonant heating. The amplitude and phase of the heat wave through the steep electron temperature gradient (ETG) region of the plasma are used to determine a transient electron thermal diffusivity that is close to the steady-state diffusivity. The low stiffness in the region between 0.2 r/a 0.4 agrees with the scaling of the steady-state heat flux with temperature gradient in this region. These experimental results are compared to gyrokinetic calculations in a flux-tube geometry using the gyrokinetic electromagnetic numerical experiment code with two kinetic species. Linear simulations show that the ETG mode may be experimentally relevant within r/a 0.2, while the Trapped Electron Mode (TEM) is the dominant long-wavelength microturbulence instability across most of the plasma. The TEM is primarily driven by the density gradient. Non-linear calculations of the saturated heat flux driven by the TEM and ETG bracket the experimental heat flux. V C 2015 AIP Publishing LLC.

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Section: Comparison To Gyrokinetic Calculationsmentioning

confidence: 99%

Profile stiffness measurements in the Helically Symmetric experiment and comparison to nonlinear gyrokinetic calculationsa)

et al. 2015

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“…Therefore, recent studies 6,7 have been performed on the ETG instabilities and the results seem to be consistent with some experimental observations. 8 At the same time, however, some experimental observations 9 seem to agree well with the model based on other instabilities, for example, the trapped electron mode-ion temperature gradient ͑ITG͒ driven mode. 10 Moreover, it is noted that not all tokamaks observed strong stiffness in electron temperature profile.…”

Section: Introductionmentioning

confidence: 62%

Short wavelength electron temperature gradient instability in toroidal plasmas

et al. 2005

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The electron temperature gradient (ETG) driven mode in the very short wavelength region k⊥ρe>1 is identified with a gyrokinetic integral equation code in toroidal plasmas. This “double-humped” growth rate of the conventional ETG and short wavelength ETG modes is attributed to the toroidal drift resonance mechanism and the nonmonotonic behavior of normalized real frequency as the poloidal wavelength varies. This instability provides a possibility existence of a kind of turbulence source with very small size of cells. However, the wavelength of the short wavelength ETG mode is too short and induced transport may be small unless there are inverse cascade effects. In addition, the critical threshold of electron temperature gradient (R∕LTe)c for the short wavelength ETG mode is higher than that for the conventional ETG mode.

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“…Here we describe the finite electron Larmor radius (gyrofluid) fluid model Horton, et al (1990)]. The model was used for the analysis of the Tore Supra discharges [Horton, et al (2004);Horton, et al (2005)] and upgraded [Kim, et al (2006)] with electron Landau damping effect [Hammett and Perkins (1990)] for NSTX. The model is constructed in a local toroidal geometry where the magnetic curvature and grad-B drifts are kept.…”

Section: Ecrh Driven Dischargesmentioning

confidence: 99%

“…The gyroBohm heat diffusivity with length scale qρ e and time scale L Te /v Te [Horton, et al (2004)] is…”

Section: Validation Analysis Of the Etg Modelmentioning

confidence: 99%