Anomalous particle pinch in tokamaks

Miskane, F.; Garbet, X.; Dezairi, A.; Saifaoui, D.

doi:10.1063/1.1308082

Cited by 40 publications

(48 citation statements)

References 35 publications

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“…Indeed first-principles based models, either fully nonlinear [17,18,19] or with quasi-linear approximation [9,20] have found qualitative agreement with some of the experimental trends. These and other theoretical works have disclosed the basic mechanisms that drive the off-diagonal particle transport terms [21,22,23,24,25,26,27,28]. We shall briefly summarize the previous results in a particular fashion, to put in evidence how all the linear wave-particle resonance physics ultimately leads to the known theoretical results.…”

Section: Introductionmentioning

confidence: 98%

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The role of ion and electron electrostatic turbulence in characterizing stationary particle transport in the core of tokamak plasmas

Fable¹,

Angioni

Sauter

2009

Plasma Phys. Control. Fusion

106

173

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Abstract. A general feature of particle transport in the core of Tokamak plasmas is that, when core particle sources are small, a stationary peaked density profile is provided by a balance of outward diffusion and inward convection, driven by either neoclassical or turbulent mechanisms. The turbulent contribution to the off-diagonal elements of the transport matrix is very sensitive on the type of dominant instability of the background turbulence. We present here a detailed quasilinear gyrokinetic analysis of stationary turbulent particle transport by means of analytical and numerical calculations to show how the actual parametric dependence of the stationary normalized density gradient can strongly vary between an Ion Temperature Gradient (ITG) dominated turbulence and a Trapped Electron Mode (TEM) dominated turbulence regime. It is also shown how the maximal achievable normalized density gradient is reached when the turbulence regime is in a mixed state. This result is interpreted as the interplay of different physical mechanisms arising from (linear) wave-particle resonances. The results presented here are addressed to interpret some of the still unresolved issue in interpreting known experimental results.

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Section: Introductionmentioning

confidence: 98%

“…Because of the E − 3/2 T kernel in thermodiffusion, integrating with a delta function in v and a Maxwellian in v ⊥ one finds that C 26,38]). For the other pinch with kernel ∼ ω, the contribution is C (p) P ≈ −ω R /k y eB 0 R/T , i.e.…”

Section: Basic Physical Mechanisms Behind C T and C Pmentioning

confidence: 99%

The role of ion and electron electrostatic turbulence in characterizing stationary particle transport in the core of tokamak plasmas

Fable¹,

Angioni

Sauter

2009

Plasma Phys. Control. Fusion

106

173

View full text Add to dashboard Cite

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“…The two primary effects of turbulence on particle transport are turbulent equipartition (TEP) [20] and anomalous thermodiffusion (THD) [21]. The former, while significant in strongly heated L-mode discharges, vanishes at zero magnetic shear and is proportional to the temperature gradient scale length and thus becomes negligible in the case of a transport barrier with a reversed shear profile.…”

Section: The Properties and Dynamics Of Eitbsmentioning

confidence: 99%

The physics of electron internal transport barriers in the TCV tokamak

et al. 2007

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Electron internal transport barriers (eITBs) are generated in the TCV tokamak with strong electron cyclotron resonance heating in a variety of conditions, ranging from steady-state fully noninductive scenarios to stationary discharges with a finite inductive component and finally to transient current ramps without current drive. The confinement improvement over L-mode ranges from 3 to 6; the bootstrap current fraction is invariably large and is above 70% in the highest confinement cases, with good current profile alignment permitting the attainment of steady state. Barriers are observed both in the electron temperature and density profiles, with a strong correlation both in location and in steepness. The dominant role of the current profile in the formation and properties of eITBs has been conclusively proven in a TCV experiment exploiting the large current drive efficiency of the Ohmic transformer: small current perturbations accompanied by negligible energy transfer dramatically alter the confinement. The crucial element in the formation of the barrier is the appearance of a central region of negative magnetic shear, with the barrier strength improving with increasingly steep shear. This connection has also been corroborated by transport modelling assisted by gyrofluid simulations. Rational safety-factor (q) values do not appear to play a role in the barrier formation, at least in the q range 1.3-2.3, as evidenced by the smooth dependence of the confinement enhancement on the loop voltage over a broad eITB database. MHD mode activity is however influenced by rational q values and results in a complex, sometimes cyclic, dynamic evolution.

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“…Results valid in general tokamak geometry have also been obtained. 3,4,10 In stellarators, there is experimental evidence of anomalous pinches, too. 3,4,10 In stellarators, there is experimental evidence of anomalous pinches, too.…”

Section: Introductionmentioning

confidence: 99%

Curvature particle pinch in tokamak and stellarator geometry

2007

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A study of the curvature pinch effect in various fusion devices (both tokamaks and stellarators) is presented. Canonical density profiles are calculated employing the theory developed by M. B. Isichenko, A. V. Gruzinov, P. H. Diamond, and P. N. Yushmanov [Phys. Plasmas 3, 1916 (1995)]. In tokamaks, it is found that the curvature pinch is relatively strong (especially in a spherical tokamak) and usually leads to a peaked density profile. In stellarators, the curvature pinch is weaker and can have either sign.

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Anomalous particle pinch in tokamaks

Cited by 40 publications

References 35 publications

The role of ion and electron electrostatic turbulence in characterizing stationary particle transport in the core of tokamak plasmas

The role of ion and electron electrostatic turbulence in characterizing stationary particle transport in the core of tokamak plasmas

The physics of electron internal transport barriers in the TCV tokamak

Curvature particle pinch in tokamak and stellarator geometry

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