Existence of ion temperature gradient driven shear Alfvén instabilities in tokamaks

Zonca, F.; Chen, Liu; Dong, J. Q.; Santoro, R. A.

doi:10.1063/1.873449

Cited by 118 publications

(196 citation statements)

References 16 publications

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“…The physics at the low-frequency part of the SAW spectrum is one such topic. At low frequencies, the bulk-plasma kinetic effects become important [37,38] (because the core diamagnetic frequency becomes comparable to the frequency of the mode). A first-principle non-perturbative gyrokinetic PIC approach seems to be an appropriate tool for addressing this regime.…”

Section: Discussionmentioning

confidence: 99%

Global particle-in-cell simulations of fast-particle effects on shear Alfvén waves

2009

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Section: Discussionmentioning

confidence: 99%

Global particle-in-cell simulations of fast-particle effects on shear Alfvén waves

2009

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“…Additionally, it is important to remember that the physics of energetic ions in ITER will be different with respect to the JET DTE1 campaign of 1997, namely due to the different ratio between the width of the αs orbit and the machine size (∼1/3 during DTE1 in JET compared with ∼1/6 to ∼1/10 as expected for ITER), and between the birth energy of the αs and E αCRIT (∼30 during DTE1 in JET compared with ∼15 to ∼20 as expected for ITER). Such differences mean that the micro-turbulent spectrum will importantly interact with Alfvén turbulence in ITER, thus affecting the overall turbulent transport [68,69]. Hence, timedependent nonlinear simulations will be needed to study and possibly optimize the various ITER operational scenarios and improve the predictions for the efficiency of this mechanism for ITG turbulence stabilization in ITER.…”

Section: Conclusion and An Outlook For Future Experimental And Modelmentioning

confidence: 99%

A phenomenological explanation for the anomalous ion heating observed in the JET alpha-heating experiment of 1997

Testa¹,

Albergante²

2012

Nucl. Fusion

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In the so-called 'alpha-heating' experiment performed on the JET tokamak during the deuterium-tritium campaign of 1997, the ion temperature was found to be far exceeding (both in absolute value and in its rise time) the level that could have been expected from direct collisional heating by the fusion-born alpha particles themselves and energy equipartition with the electrons. To date, no explanation has been put forward for this long standing puzzle, despite much work having been performed on this subject in the early 2000s.Two analysis methods that have recently become available have been employed to re-analyse these observations of an anomalous ion heating. First, an algorithm based on the sparse representation of signals has been used to analyse magnetic, reflectometry and electron-cyclotron emission measurements of the turbulence spectra in the drift-wave range of frequencies. This analysis has then been complemented with turbulence simulations performed with the GENE code.We find, both experimentally and in the simulations, that the presence of a minority, but sufficiently large, population of fusion-born alpha particles that have not yet fully thermalized stabilizes the turbulence in the ion-drift direction, but practically does not affect the turbulence in the electron-drift direction. We link such stabilization of the ion-drift-wave turbulence to the increase in the ion temperature above the level achieved in similar discharges that did not have (at all or enough) alpha particles. When the fusion-born alpha particles have fully thermalized, the turbulence spectrum in the ion-drift direction reappears at somewhat larger amplitudes, which we link to the ensuing reduction in the ion temperature. This phenomenological dynamics fully corresponds to the actual experimental observations. By taking into account an effect of the alpha particles that had not been previously considered, our new analysis finally presents a phenomenological explanation for the so-far-unexplained anomalous ion heating observed in the JET alpha-heating experiment of 1997.Through the formulation of an empirical criterion for ion-drift-wave turbulence stabilization by fusion-born alpha particles, we also show why similar observations were not made in the other deuterium-tritium experiments run so far in JET and TFTR. This allows assessing the operational domain for this stabilization mechanism for ion-drift-wave turbulence in future burning plasma experiments such as ITER, which may open a new path towards the sustainment of a high energy gain in such forthcoming devices.

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“…For the study of electromagnetic perturbations, passing electrons must also be considered as non-adiabatic, and the system of equations is to be completed by Ampère's law. In addition to the ITG and TEM modes, the model describes another branch of micro-instabilities, named Alfvénic-ITG [58] or kinetic ballooning mode [59]. For finite but small β, it is sufficient to consider a two-potential approach (φ, A ) which neglects the perturbations of the magnetic field parallel to the equilibrium (δB ≈ 0).…”

Section: Gyrokinetic Model and Its Variationsmentioning

confidence: 99%

First principles based simulations of instabilities and turbulence

Villard

Angelino

Bottino

et al. 2004

Plasma Phys. Control. Fusion

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It is now widely believed that low frequency turbulence developing from smallscale instabilities is responsible for the phenomenon of anomalous transport generally observed in magnetic confinement fusion experiments. The microinstabilities are driven by gradients of equilibrium density, ion and electron temperatures and magnetic field strength. Gyrokinetic theory is based on the Vlasov-Maxwell equations and, consistent with the ordering, averages out the fast particle gyromotion, reducing the phase space from 6 to 5 dimensions. Solving the resulting equations is a non-trivial task. Difficulties are associated with the magnetic confinement geometry, the strong disparities in space and time scales perpendicular and parallel to B, the different time scales of ion and electron dynamics, and the complex nonlinear behaviour of the system. The main numerical methods are briefly presented together with some recent developments and improvements to the basic algorithms. Recent results are shown, with emphasis on the roles of zonal E ×B flows, of parallel nonlinearity and of toroidal coupling on the saturation of ion temperature gradient (ITG) driven turbulence in tokamaks.

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Existence of ion temperature gradient driven shear Alfvén instabilities in tokamaks

Cited by 118 publications

References 16 publications

Global particle-in-cell simulations of fast-particle effects on shear Alfvén waves

Global particle-in-cell simulations of fast-particle effects on shear Alfvén waves

A phenomenological explanation for the anomalous ion heating observed in the JET alpha-heating experiment of 1997

First principles based simulations of instabilities and turbulence

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