Plasma shaping effects on tokamak scrape-off layer turbulence

Riva, Fabio; Lanti, Emmanuel; Jolliet, S.; Ricci, Paolo

doi:10.1088/1361-6587/aa5322

Cited by 26 publications

(50 citation statements)

References 63 publications

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“…Enhanced energy confinement at negative triangularity, explained by a reduction of turbulent transport in the confined region [21], is confirmed. The effect of triangularity on scrape-off layer turbulence could be a possible explanation for smaller λ out q for decreasing δ up , in qualitative agreement with turbulence simulation in limited plasmas [31]. Helium discharges exhibit a larger λ q compared to deuterium, in line with previous studies on JET [28,29] and ASDEX Upgrade [27].…”

Section: Discussionsupporting

confidence: 88%

“…This is in line with the increased T e,edge and stored energy W MHD at constant heating power in the presented TCV database. Recently, reduced turbulent transport has been reported for the scrape-off layer in elongated limited plasmas with negative triangularity using linear and nonlinear simulations [31]. This is in qualitative agreement with the observed decreasing λ out q with decreasing δ up .…”

Section: Turbulent Transportsupporting

confidence: 84%

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Dependence of the L-Mode scrape-off layer power fall-off length on the upper triangularity in TCV

Faitsch

Maurizio

Gallo

et al. 2018

Plasma Phys. Control. Fusion

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This paper reports on experimental observations on TCV with a scan in upper triangularity δup, including negative triangularity, focusing on the power fall-off length λq in L-Mode. The upper triangularity is scanned from -0.28 to 0.47. Smaller λ out q is measured at the outer divertor target for decreasing δup together with higher edge temperature T e,edge leading to increased confinement. This effect is observed for both magnetic drift directions for discharges in deuterium and helium. In helium larger λq values are observed compared to deuterium. The power fall-off length at the inner divertor target λ in q has a non monotonic behaviour with changing triangularity. The largest values are around δup = 0. The ratio λ in q /λ out q increases for decreasing δup for positive triangularity and is approximately constant for negative triangularity. λ out q is compared to available scaling laws. Partial agreement is only observed for a scaling law containing a proxy for T e,edge at ASDEX Upgrade [Sieglin, PPCF 2016]. Extending this scaling to TCV and using T e,edge at ρ pol = 0.95 suggests that λ out q is independent of machine size λ L−Mode q [mm] = 165 · B pol [T] −0.66 · A[u] −0.15 · T e,edge [eV] −0.93 · R[m] −0.03 . Possible explanations for smaller λ out q for decreasing δup is a reduction in turbulence or a direct effect of increasing T e,edge .

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Section: Discussionsupporting

confidence: 88%

Section: Turbulent Transportsupporting

confidence: 84%

Dependence of the L-Mode scrape-off layer power fall-off length on the upper triangularity in TCV

Faitsch

Maurizio

Gallo

et al. 2018

Plasma Phys. Control. Fusion

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“…III of Ref. 72. Considering circular magnetic geometries in the infinite aspect ratio, the resulting system of equations writes…”

Section: -9mentioning

confidence: 99%

“…(14)- (18), a numerical code was developed, which evaluates c as a function of the parameters R 0 /L n , g, , q, and k Y , as detailed in Ref. 72.…”

Section: -9mentioning

confidence: 99%

Three-dimensional simulations of plasma turbulence in the RFX-mod scrape-off layer and comparison with experimental measurements

et al. 2018

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The tokamak scrape-off layer (SOL) plasma dynamics is investigated in a circular limiter configuration with a low edge safety factor. Focusing on the experimental parameters of two ohmic tokamak inner-wall limited plasma discharges in RFX-mod [Sonato et al., Fusion Eng. Des. 74, 97 (2005)], nonlinear SOL plasma simulations are performed with the GBS code [Ricci et al., Plasma Phys. Controlled Fusion 54, 124047 (2012)]. The numerical results are compared with the experimental measurements, assessing the reliability of the GBS model in describing the RFX-mod SOL plasma dynamics. It is found that the simulations are able to quantitatively reproduce the RFX-mod experimental measurements of the electron plasma density, electron temperature, and ion saturation current density (jsat) equilibrium profiles. Moreover, there are indications that the turbulent transport is driven by the same instability in the simulations and in the experiment, with coherent structures having similar statistical properties. On the other hand, it is found that the simulation results are not able to correctly reproduce the floating potential equilibrium profile and the jsat fluctuation level. It is likely that these discrepancies are, at least in part, related to simulating only the tokamak SOL region, without including the plasma dynamics inside the last close flux surface, and to the limits of applicability of the drift approximation. The turbulence drive is then identified from the nonlinear simulations and with the linear theory. It results that the inertial drift wave is the instability driving most of the turbulent transport in the considered discharges.

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“…Flux surface shaping effects [18,19] in more general tokamak or stellarator geometry on SOL filaments [20] are here neglected for simplicity.…”

Section: Gyrofluid Model and Computationmentioning

confidence: 99%

Isotope effect on filament dynamics in fusion edge plasmas

Meyer

Kendl

2017

Plasma Phys. Control. Fusion

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Abstract. The influence of the ion mass on filament propagation in the scrape-off layer of toroidal magnetised plasmas is analysed for various fusion relevant majority species, like hydrogen isotopes and helium, on the basis of a computational isothermal gyrofluid model for the plasma edge. Heavy hydrogen isotope plasmas show slower outward filament propagation and thus improved confinement properties compared to light isotope plasmas, regardless of collisionality regimes. Similarly, filaments in fully ionised helium move more slowly than in deutrium. Different mass effects on the filament inertia through polarisation, finite Larmor radius, and parallel dynamics are identified.

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Plasma shaping effects on tokamak scrape-off layer turbulence

Cited by 26 publications

References 63 publications

Dependence of the L-Mode scrape-off layer power fall-off length on the upper triangularity in TCV

Dependence of the L-Mode scrape-off layer power fall-off length on the upper triangularity in TCV

Three-dimensional simulations of plasma turbulence in the RFX-mod scrape-off layer and comparison with experimental measurements

Isotope effect on filament dynamics in fusion edge plasmas

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