On finite β stabilization of the toroidal ion temperature gradient mode

Hirose, Akira

doi:10.1063/1.873866

Cited by 26 publications

(26 citation statements)

References 8 publications

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“…Our analysis of the finite-β suppression of the ITG mode follows that of Hirose [31], making the appropriate modifications for the RFP geometry (see Sec. II).…”

Section: A Itg Beta Suppressionmentioning

confidence: 99%

“…Finite-β suppression of ITG (a linear effect which may be amplified nonlinearly [30]) has been a topic of study in the context of tokamaks [31], and that analysis will be applied here to ITG in the RFP. In the RFP, ITG growth rates can still be quite strong at values of β where tokamak ITG is typically stable [21], as can be seen in Fig.…”

Section: A Itg Beta Suppressionmentioning

confidence: 99%

“…[31], we are able to derive the stability condition, with certain terms adjusted to account for the RFP generalizations,…”

Section: A Itg Beta Suppressionmentioning

confidence: 99%

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Gyrokinetic studies of microinstabilities in the reversed field pinch

2013

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An analytic equilibrium, the Toroidal Bessel Function Model, is used in conjunction with the gyrokinetic code GYRO to investigate the nature of microinstabilities in a reversed field pinch (RFP) plasma. The effect of the normalized electron plasma pressure (β) on the characteristics of the microinstabilities is studied. A transition between an ion temperature gradient (ITG) driven mode and a microtearing mode as the dominant instability is found to occur at a β value of approximately 4.5%. Suppression of the ITG mode occurs as in the tokamak, through coupling to shear Alfvén waves, with a critical β for stability higher than its tokamak equivalent due to a shorter parallel connection length. There is a steep dependence of the microtearing growth rate on temperature gradient suggesting high profile stiffness. There is evidence for a collisionless microtearing mode. The properties of this mode are investigated, and it is found that curvature drift plays an important role in the instability. * dcarmody@wisc.edu

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“…Our analysis of the finite-β suppression of the ITG mode follows that of Hirose [31], making the appropriate modifications for the RFP geometry (see Sec. II).…”

Section: A Itg Beta Suppressionmentioning

confidence: 99%

Section: A Itg Beta Suppressionmentioning

confidence: 99%

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Gyrokinetic studies of microinstabilities in the reversed field pinch

2013

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“…Linear stabilization of ITG modes by electromagnetic (EM) effects (i.e., finite-β) is well known [9,10]. However, recent nonlinear simulations of finite-β ITG turbulence have highlighted that nonlinear EM-stabilizationi.e.…”

Section: Introductionmentioning

confidence: 99%

Electromagnetic stabilization of tokamak microturbulence in a high-βregime

Citrin

García

Görler

et al. 2014

Plasma Phys. Control. Fusion

146

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The impact of electromagnetic stabilization and flow shear stabilization on ITG turbulence is investigated. Analysis of a low-β JET L-mode discharge illustrates the relation between ITG stabilization, and proximity to the electromagnetic instability threshold. This threshold is reduced by suprathermal pressure gradients, highlighting the effectiveness of fast ions in ITG stabilization. Extensive linear and nonlinear gyrokinetic simulations are then carried out for the high-β JET hybrid discharge 75225, at two separate locations at inner and outer radii. It is found that at the inner radius, nonlinear electromagnetic stabilization is dominant, and is critical for achieving simulated heat fluxes in agreement with the experiment. The enhancement of this effect by suprathermal pressure also remains significant. It is also found that flow shear stabilization is not effective at the inner radii. However, at outer radii the situation is reversed. Electromagnetic stabilization is negligible while the flow shear stabilization is significant. These results constitute the high-β generalization of comparable observations found at low-β at JET. This is encouraging for the extrapolation of electromagnetic ITG stabilization to future devices. An estimation of the impact of this effect on the ITER hybrid scenario leads to a 20% fusion power improvement.

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“…First, in the ETG mode, charge neutrality does not necessarily hold because of short wavelength nature. Second, while the ITG mode can be stabilized by a modest plasma factor through the coupling of electron dynamics to the magnetic perturbation [5], the ETG mode is quite resilient against finite stabilization which can occur through equilibrium modification only at such a large (the ballooning parameter) as to cause an effective magnetic drift reversal [6]. If isomorphism between the ETG and ITG modes holds, the mixing length estimate for the electron thermal diffusivity would be of the order of [7] e ' v Te L n 2 e ; (1) which is smaller than the ion thermal diffusivity due to the ITG mode by approximately a factor of m i =m e p , and thus would not be relevant to the anomalous electron thermal transport commonly observed in magnetic confinement devices.…”

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confidence: 99%

Electron Thermal Diffusivity due to the Electron Temperature Gradient Mode

Hirose

2004

Phys. Rev. Lett.

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Charge neutrality breaks down in the short wavelength toroidal electron temperature gradient mode. In contrast to the ion temperature gradient mode, the wave number normalized by the Debye wave number, k/k(De), appears as a natural scale parameter, rather than the finite Larmor radius parameter k( perpendicular )rho(e). The growth rate and consequent mixing length estimate yields an electron thermal diffusivity large enough to be relevant to tokamaks.

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On finite β stabilization of the toroidal ion temperature gradient mode

Cited by 26 publications

References 8 publications

Gyrokinetic studies of microinstabilities in the reversed field pinch

Gyrokinetic studies of microinstabilities in the reversed field pinch

Electromagnetic stabilization of tokamak microturbulence in a high-βregime

Electron Thermal Diffusivity due to the Electron Temperature Gradient Mode

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