Role of nonadiabatic untrapped electrons in global electrostatic ion temperature gradient driven modes in a tokamak

Chowdhury, Jugal; Ganesh, R.; Angelino, Paolo; Václavík, J.; Villard, L.; Brunner, S.

doi:10.1063/1.2957917

Cited by 16 publications

(11 citation statements)

References 22 publications

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“…When accounting for the fully kinetic response of the electrons, fine structures related to their non-adiabatic response appear on the eigenmode structures in the vicinity of MRSs 6,7 . Their presence in non-linear simulations has been observed as well [8][9][10] , potentially altering the electron particle flux 11 .…”

Section: Introductionmentioning

confidence: 99%

How non-adiabatic passing electron layers of linear microinstabilities affect turbulent transport

et al. 2015

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The response of passing electrons in ion temperature gradient (ITG) and trapped electron mode (TEM) microturbulence regimes is investigated in tokamak geometry making use of the flux-tube version of the gyrokinetic code GENE. Results are obtained using two different electron models, fully kinetic and hybrid in which passing particles are forced to respond adiabatically while trapped are handled kinetically. Comparing linear eigenmodes obtained with these two models enables to systematically isolate fine radial structures located at corresponding mode rational surfaces, clearly resulting from the non-adiabatic passing electron response. Non-linear simulations show that these fine structures on the non-axisymmetric modes survive in the turbulent phase. Furthermore, through non-linear coupling to axisymmetric modes, they induce radial modulations in the effective profiles of density, ion/electron temperature and E × B shearing rate. Finally, the passing electron channel is shown to significantly contribute to the transport levels, at least in our ITG case. Also shown is that the passing electrons significantly influence the E × B saturation mechanism of turbulence fluxes.

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Section: Introductionmentioning

confidence: 99%

How non-adiabatic passing electron layers of linear microinstabilities affect turbulent transport

et al. 2015

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“…The adiabatic electron model, although very efficient from the practical point of view of computer resources, is not always applicable since the adiabatic assumption does not hold for trapped electrons nor for passing electrons located at low order mode rational flux surfaces (i.e. where the safety factor is rational: q s = m/n, m and n being integers) [1][2][3]. In particular, the adiabatic electron model does not allow the addressing of the electrostatic TEMs nor the electromagnetic instabilities.…”

Section: Introductionmentioning

confidence: 99%

Global gyrokinetic simulations of TEM microturbulence

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Brunner

Villard

et al. 2013

Plasma Phys. Control. Fusion

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Global gyrokinetic simulations of electrostatic temperature-gradient-driven trapped-electron-mode (TEM) turbulence using the δf particle-in-cell code ORB5 are presented. The electron response is either fully kinetic or hybrid, i.e. considering kinetic trapped and adiabatic passing electrons. A linear benchmark in the TEM regime against the Eulerian-based code GENE is presented. Two different methods for controlling the numerical noise, based, respectively, on a Krook operator and a so-called coarse-graining approach, are discussed and successfully compared. Both linear and non-linear studies are carried out for addressing the issue of finite-ρ * -effects and finite electron collisionality on TEM turbulence. Electron collisions are found to damp TEMs through the detrapping process, while finite-ρ * -effects turn out to be important in the non-linear regime but very small in the linear regime. Finally, the effects of zonal flows on TEM turbulence are briefly considered as well and shown to be unimportant in the temperature-gradient-driven TEM regime. Consistently, basically no difference is found between linear and non-linear critical electron temperature gradients in the TEM regime.

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“…27. In the present work, the effect of nonadiabaticity of passing electrons is extended to ITG coupled TEM ͑ITG-TEM͒ and to pure TEMs.…”

Section: Resultsmentioning

confidence: 99%

“…Recently such a study addressing the effect of nonadiabatic passing electrons on the ITG mode has been reported in Ref. 27. Here the results accounting for all the four subgroups of species are presented, which include ITG, ITG-TEM, and TEMs.…”

Section: Introductionmentioning

confidence: 99%

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A comprehensive gyrokinetic description of global electrostatic microinstabilities in a tokamak

et al. 2009

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It is believed that low frequency microinstabilities such as ion temperature gradient ͑ITG͒ driven modes and trapped electron modes ͑TEMs͒ are largely responsible for the experimentally observed anomalous transport via the ion and electron channels in a tokamak. In the present work, a comprehensive global linear gyrokinetic model incorporating fully kinetic ͑trapped and passing͒ electrons and ions, actual ion to electron mass ratio, radial coupling, and profile variation is used to investigate the ITG driven modes and pure TEMs. These modes are found to exhibit multiscale structures in the presence of nonadiabatic passing electrons. The multiscale structure is related to the large nonadiabaticity of electrons in the vicinity of mode rational magnetic surfaces and leads to reduced mixing length estimates of transport compared to those obtained from adiabatic electron models.

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Role of nonadiabatic untrapped electrons in global electrostatic ion temperature gradient driven modes in a tokamak

Cited by 16 publications

References 22 publications

How non-adiabatic passing electron layers of linear microinstabilities affect turbulent transport

How non-adiabatic passing electron layers of linear microinstabilities affect turbulent transport

Global gyrokinetic simulations of TEM microturbulence

A comprehensive gyrokinetic description of global electrostatic microinstabilities in a tokamak

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