Modeling snowflake divertors in MAST-U tokamak using UEDGE code

Khrabry, Alexander; Soukhanovskii, V.; Rognlien, T. D.; Umansky, M.; Moulton, D.; Harrison, James R.

doi:10.1016/j.nme.2020.100896

Cited by 6 publications

(9 citation statements)

References 22 publications

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“…If stimulated emission and absorption are taken into account as in the optically thick case, the radiation rates also include the Einstein B i j coefficients and are coupled to the mean radiation intensity integrated over the photon distribution (described by the spectral emission or absorption line profile) [26,27]. The optical depth τ ν is used to characterize plasma opacity to line radiation in a particular direction (along a ray), as No R = 0.98, A = 0.98 [24,25] defined by:…”

Section: Radiation Transport In Divertor Plasmasmentioning

confidence: 99%

“…For SF divertor configurations, the UEDGE code was used with the same assumptions as those used in the SOLPS SXD simulations [24]. Both the SF-plus configuration with an additional poloidal field null in the private flux region (PFR), and the SF-minus, with an additional poloidal field null in the common flux region, in the outer SOL, were modeled.…”

Section: Solps Uedge and Cretin Modelsmentioning

confidence: 99%

“…Both the SF-plus configuration with an additional poloidal field null in the private flux region (PFR), and the SF-minus, with an additional poloidal field null in the common flux region, in the outer SOL, were modeled. The generated UEDGE database included the SF-plus and SF-minus configurations with different inter-null distances, different levels of plasma transport (mixing) in the SF null region, and upstream density scans n OMP e,sep = (0.25 − 1.9) × 10 −19 m −3 for detachment studies [24,25].…”

Section: Solps Uedge and Cretin Modelsmentioning

confidence: 99%

“…Divertor power exhaust via radiative detachment of the divertor strike points (SPs) is considered to be a leading heat flux and material erosion mitigation strategy for future tokamaks [14], including advanced divertor configurations [22]. Recent modeling studies have shown that both the SXD and SF divertor configurations may have an advantage over the standard divertor as they reach highly radiative (detached) regimes at lower upstream densities (cf the standard divertor) [20,[23][24][25]. However, radiation transport (radiation trapping) may change the advanced divertor plasma properties thus leading to a reduction of the geometry benefits.…”

Section: Introductionmentioning

confidence: 99%

“…The MAST-U SXD configuration features an expanded tightly baffled outer divertor leg plasma with a radial spatial scale of L ∼ 60 cm. In the SF divertor configurations developed for MAST-U [24], the primary and secondary SPs land on vertical targets in the divertor throat, potentially leading to high deuterium recycling fluxes and high neutral deuterium densities.…”

Section: Introductionmentioning

confidence: 99%

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Modeling of deuterium and carbon radiation transport in MAST-U tokamak advanced divertors

Soukhanovskii¹,

Khrabry²,

Scott³

et al. 2022

Nucl. Fusion

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Modest effects of deuterium and carbon radiation opacity in the Super- X and snowflake divertor plasmas are predicted for MAST Upgrade tokamak with core plasma input power 2.5-5 MW and plasma current 1 MA. The radiation transport modeling is based on the SOLPS-EIRENE and UEDGE code divertor plasma predictions. Two radiation transport models are used: one is based on a full radiation transport equation implemented in the radiation transport and collisional- radiative code CRETIN (without feedback on the background plasma), and another is an internal self-consistent UEDGE model with ionization, recombination, and heating rates corrected for Lyα line trapping based on the escape probability model implemented in CRETIN. In MAST-U, the Super-X and snowflake divertor plasmas are predicted to reach detached regimes at lower upstream densities than the standard divertor, and the conclusion still holds with radiation transport effects included. At neutral densities ≤ 1020 m−3, modest Lyα deuterium line trapping with optical depths 10-15 is predicted in the Super-X divertor. Divertor plasmas are optically thin to other Lyman and Balmer lines, as well as to strong C III and C IV lines that are responsible for most of divertor radiated power. Insignificant changes (within a few percent) to divertor deuterium ionization and recombination rates are found. Radiation fluxes on outer divertor target are modified within a factor of 2-3 when the radiation transport is accounted for, and a similar variation is found due to the line shape models that define the absorption and emission line profiles in the radiation transport modeling. The predicted Lyman and Balmer spectral intensities are significantly modified due to radiation trapping. A measurement of divertor radiation transport effects is discussed using the Lyβ /Baα line ratio. In the snowflake divertor configuration, divertor plasmas are found to be optically thin to Lyman series lines within a large range of parameter variations that include upstream density, divertor transport coefficients, and magnetic configurations. Modest radiation transport effects are only found in a few cases with strongest divertor transport and magnetic configurations closest to the ideal snowflake configuration, however, the plasma background models that were used are yet to be validated with an experiment.

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Section: Radiation Transport In Divertor Plasmasmentioning

confidence: 99%

Section: Solps Uedge and Cretin Modelsmentioning

confidence: 99%

Section: Solps Uedge and Cretin Modelsmentioning

confidence: 99%

Section: Introductionmentioning

confidence: 99%

Section: Introductionmentioning

confidence: 99%

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Modeling of deuterium and carbon radiation transport in MAST-U tokamak advanced divertors

Soukhanovskii¹,

Khrabry²,

Scott³

et al. 2022

Nucl. Fusion

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UEDGE modeling of plasma detachment of CFETR with ITER‐like divertor geometry by external impurity seeding

Zhang,

Sang,

Zhao

et al. 2024

Contrib. Plasma Phys

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Efficient handling of high heat flux on the plasma‐facing components, particularly the divertor targets, poses a significant challenge for the Chinese Fusion Engineering Testing Reactor (CFETR) with fusion power of Gigawatt. This work investigates the divertor plasma detachment of CFETR with a standard ITER‐like divertor geometry by neon (Ne) or argon (Ar) impurity seeding using UEDGE code. The cross‐field drifts terms are switched off, and fluid neutral models and a “fixed‐fraction” impurity model are applied to enable efficient simulations for the study of CFETR detachment. In order to reduce the heat load on the divertor targets below the acceptable level (<10 MW/m2), the impurity fraction (f), pumping speed (S), and upstream density are varied to identify the suitable operations window during Ne seeding. The effects of Ne and Ar impurities on the plasma detachment are compared. It is found that with the power across the core‐edge interface PSOL = 200 MW and separatrix density of 2.8 1019 , Ne impurity fraction ≥1.7%, and Ar impurity fraction ≥0.24% can achieve the partial detachment. Achieving similar total radiation power (˜148 MW), the Ne fraction is 2.3% and the Ar fraction is 0.24%. Moreover, the simulation results indicate that Ar exhibits better power radiation efficiency and core compatibility compared with Ne.

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