Impact of the plasma geometry on divertor power exhaust: experimental evidence from TCV and simulations with SolEdge2D and TOKAM3X

Gallo, A.; Fedorczak, N.; Elmore, S.; Maurizio, R.; Reimerdes, H.; Theiler, C.; Tsui, C.; Boedo, J.A.; Faitsch, M.; Bufferand, Hugo; Ciraolo, Guido; Galassi, D.; Ghendrih, Philippe; Valentinuzzi, M.; Tamain, P.

doi:10.1088/1361-6587/aa857b

Cited by 34 publications

(47 citation statements)

References 32 publications

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“…snowflake) are discussed in [10,11,12]. The effect of divertor leg length on the heat flux profile is discussed in [13,14,15]. This paper focuses on the effect of plasma triangularity on heat flux on both divertor targets for a single null configuration with particular emphasis on negative triangularity.…”

Section: Introductionmentioning

confidence: 99%

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: Introductionmentioning

confidence: 99%

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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“…Magnetic configurations of the Tokamak à configuration variable (TCV) # 51333 (by permission from ref. ). We consider the medium leg configuration (blue solid line).…”

Section: Tcv Reference Test Case and Extraction Of The Diffusion Coefmentioning

confidence: 97%

“…In order to determine the free parameters of the reduced turbulence model described in the previous section, we use a typical L‐mode ohmic discharge on the TCV studied in ref. (TCV # 51333). The main plasma characteristics are given in Table .…”

Section: Tcv Reference Test Case and Extraction Of The Diffusion Coefmentioning

confidence: 99%

“… Left and middle : Mid‐plane profiles of density and temperature ( symbol : experimental data, lines : SolEdge2D‐Eirene simulation results with feedback procedure) from Ref. . Right : Cross‐field transport coefficients obtained from the feedback procedure…”

Section: Tcv Reference Test Case and Extraction Of The Diffusion Coefmentioning

confidence: 99%

“…In that sense, the turbulent particle flux Γ ⊥ is found to be proportional to the gradient of the density, and the proportionality constant D ⊥ is referred to the turbulent diffusivity: Γ ⊥ = − D ⊥ ∇ ⊥ n . In this framework, the SOL width, which is governed by the competition between parallel and perpendicular transport, can be found equalizing τ ∥ = L ∥ / c s and

τ_{⊥} = λ_{SOL}^{2} false/ D_{⊥}

, where τ ∥ and τ ⊥ are the parallel and perpendicular particle transport time scales, respectively, L ∥ is the characteristic parallel length of spatial variations along the SOL, and c s is the sound velocity in the plasma. Thus one obtains

λ_{SOL} = \sqrt{L_{∥} D_{⊥} false/ c_{s}}

.…”

Section: Introductionmentioning

confidence: 99%

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Optimization of turbulence reduced model free parameters based on L‐mode experiments and 2D transport simulations

Baschetti

Bufferand

Ciraolo

et al. 2018

Contributions to Plasma Physics

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In this paper, a κ−ϵ transport model is presented as a turbulence reduction tool for a typical ohmic L‐mode discharge plasma in a divertor‐configurated tokamak. Taking a Tokamak à configuration variable (TCV) study case, a feedback loop procedure is performed using the SolEdge2D code to acquire plasma diffusivity at the outer mid‐plane. The κ−ϵ model is calibrated through its free parameters with the aim of recovering the diffusivity calculated in the feedback procedure. Finally, it is shown that the model can self‐consistently calculate diffusivity in the whole domain, recovering the poloidal asymmetries due to interchange instabilities.

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Simulation of the electromagnetic characters of a Faraday‐shielded antenna in a helicon wave plasma source

Zhou

Tan

et al. 2021

Contributions to Plasma Physics

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In this article, a structure that employs a Faraday shield between the Shoji antenna and the dielectric tube, which aims to reduce the dielectric wall sputtering, is investigated for the helicon wave plasma (HWP) sources. Faraday shield is usually used between the antenna and the reaction chamber to reduce the radiation from the high electromagnetic field generation, as well as to prevent the sputtering of the antenna material from polluting the reaction chamber during the discharge. Here, the influence of the Faraday shield on the longitudinal and radial electric field of the antenna is analysed through COMSOL MultiphysicsTM. Significant attenuations of both the longitudinal and radial fields are observed in the presence of the shield. In addition, by comparing the electric field distribution under two different shielding parameters, it is found that the shielding effects are not the same. Therefore, a detailed study of two kinds of design (pitch and gap) for the shield was carried out. The results show that the pitch has a little impact on the overall shielding effect when the gap is unaltered. The best shielding performance appears when we set the pitch at T of 8 and 10. In addition, the shielding effect also becomes worse as the gap increases while the pitch remains unchanged. A relatively good shielding effect can be produced by setting the gap to the value of 4–8 mm (a gap/pitch ratio of 2/15–4/15). This work provides a theoretical basis for designing a Faraday shield structure between the antenna and the dielectric tube, which is helpful to realize stable and controllable HWP discharges.

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Impact of the plasma geometry on divertor power exhaust: experimental evidence from TCV and simulations with SolEdge2D and TOKAM3X

Cited by 34 publications

References 32 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

Optimization of turbulence reduced model free parameters based on L‐mode experiments and 2D transport simulations

Simulation of the electromagnetic characters of a Faraday‐shielded antenna in a helicon wave plasma source

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