Analysis of the neutral fluxes in the divertor region of Wendelstein 7-X under attached and detached conditions using EMC3-EIRENE

This paper analyzes the neutral fluxes in the divertor region of the W7-X standard configuration for different input powers, both under attached and detached conditions. The performed analysis is conducted through EMC3-EIRENE simulations. They show the importance of the horizontal divertor to generate neutrals, and resolve the neutral plugging in the divertor region. Simulations of detached cases show a decrease in the number of generated neutrals compared to the attached simulations, in addition to a higher fraction of the ion flux arriving on the baffles during detachment. As the ionization takes place further inside the plasma during detachment, a larger percentage of the generated neutral particles leave the divertor as neutrals. The leakage in the poloidal and toroidal direction increases, just as the fraction of collected particles at the pumping gap. The fraction of pumped particles increases with a factor two, but stays below one percent. This demonstrates that detachment with the current target geometry, although it improves the power exhaust, is not yet leading to an increased particle exhaust

Stability of iterated plasma edge transport solvers

The application of numerical transport solvers for the plasma boundary of magnetic fusion devices is related to the iterative approximation of a xed-point of a non-linear map. 2D (axisymmetric) or even 3D transport solvers are routinely applied for the quantication of steady state plasma ows. However, unstable behavior is found under certain conditions. A simple two-point model is applied to demonstrate that this kind ofunstable behavior can occur when the xed-point looses stability, resulting in a period doubling route to chaos. Furthermore, wavelike oscillations can occur at low temperatures.An adaptive relaxation scheme is presented which allows to suppress discrete and wavelike oscillations in order to stabilize the xed-point iteration

Numerical error estimation in EMC3-EIRENE for a DIII-D divertor edge plasma

status: publishe

Numerical accuracy and convergence with EMC3-EIRENE

status: publishe

通过 3-D 建模分析 Wendelstein 7-X 启动情景的螺旋刮层中的热通量特性

International audienceA crucial topic for the stellarator W7-X is the power dissipation by impurities for future island divertor scenarios. The investigation of the related heat flux distribution and profiles including the radial power fall-off length λq in the 3D stellarator SOL is less straight forward as in toroidally symmetric tokamaks. Studies with the 3D plasma edge transport code EMC3-Eirene predicted a modulation of plasma parameters with LC and correlated heterogenous heat and particle loads onto the limiters during start-up operation. The relative simple start up geometry at W7-X allows for a detailed analysis of the heat fluxes in separate helical transport channels featuring different ∥ to ⊥ transport ratios. It is shown that the SOL has two characteristic fall off domains - a near SOL and a far SOL domain which both have different power decay lengths. An increase of λq with LC in the order of ~1-1.5cm in the near SOL and ~1.8-2.8cm in the far SOL for a power scan in the range of P=0.5-2MW at nLCFS=2×1018m−3 has been found. First comparisons with IR camera data will be discussed.Un sujet crucial pour le stellarator W7-X est la dissipation de puissance par les impuretés pour les futurs scénarios de divertor insulaire. L'étude de la distribution et des profils de flux de chaleur associés, y compris la longueur de chute de puissance radiale λq dans le SOL du stellarator 3D, est moins simple que dans les tokamaks à symétrie toroïdale. Des études avec le code de transport de bord de plasma 3D EMC3-Eirene ont prédit une modulation des paramètres du plasma avec LC et des charges de chaleur et de particules hétérogènes corrélées sur les limiteurs pendant le démarrage. La géométrie de démarrage relativement simple à W7-X permet une analyse détaillée des flux de chaleur dans des canaux de transport hélicoïdaux séparés présentant différents rapports de transport ∥ à ⊥. Il est montré que le SOL a deux domaines de décroissance caractéristiques - un domaine SOL proche et un domaine SOL lointain qui ont tous deux des longueurs de décroissance de puissance différentes. Une augmentation de λq avec LC de l'ordre de ~1-1,5 cm dans le SOL proche et de ~1,8-2,8 cm dans le SOL lointain pour un balayage de puissance dans la plage de P=0,5-2MW à nLCFS=2×1018m−3 a été trouvé. Les premières comparaisons avec les données des caméras IR seront discutées

通过 3-D 建模分析 Wendelstein 7-X 启动情景的螺旋刮层中的热通量特性

International audienceA crucial topic for the stellarator W7-X is the power dissipation by impurities for future island divertor scenarios. The investigation of the related heat flux distribution and profiles including the radial power fall-off length λq in the 3D stellarator SOL is less straight forward as in toroidally symmetric tokamaks. Studies with the 3D plasma edge transport code EMC3-Eirene predicted a modulation of plasma parameters with LC and correlated heterogenous heat and particle loads onto the limiters during start-up operation. The relative simple start up geometry at W7-X allows for a detailed analysis of the heat fluxes in separate helical transport channels featuring different ∥ to ⊥ transport ratios. It is shown that the SOL has two characteristic fall off domains - a near SOL and a far SOL domain which both have different power decay lengths. An increase of λq with LC in the order of ~1-1.5cm in the near SOL and ~1.8-2.8cm in the far SOL for a power scan in the range of P=0.5-2MW at nLCFS=2×1018m−3 has been found. First comparisons with IR camera data will be discussed.Un sujet crucial pour le stellarator W7-X est la dissipation de puissance par les impuretés pour les futurs scénarios de divertor insulaire. L'étude de la distribution et des profils de flux de chaleur associés, y compris la longueur de chute de puissance radiale λq dans le SOL du stellarator 3D, est moins simple que dans les tokamaks à symétrie toroïdale. Des études avec le code de transport de bord de plasma 3D EMC3-Eirene ont prédit une modulation des paramètres du plasma avec LC et des charges de chaleur et de particules hétérogènes corrélées sur les limiteurs pendant le démarrage. La géométrie de démarrage relativement simple à W7-X permet une analyse détaillée des flux de chaleur dans des canaux de transport hélicoïdaux séparés présentant différents rapports de transport ∥ à ⊥. Il est montré que le SOL a deux domaines de décroissance caractéristiques - un domaine SOL proche et un domaine SOL lointain qui ont tous deux des longueurs de décroissance de puissance différentes. Une augmentation de λq avec LC de l'ordre de ~1-1,5 cm dans le SOL proche et de ~1,8-2,8 cm dans le SOL lointain pour un balayage de puissance dans la plage de P=0,5-2MW à nLCFS=2×1018m−3 a été trouvé. Les premières comparaisons avec les données des caméras IR seront discutées

First Application of 3D Peripheral Plasma Transport Code EMC3-EIRENE to Heliotron J

The 3D peripheral plasma and neutral transport code, EMC3-EIRENE was applied to the Heliotron J with a wide and flexible controllability of magnetic configuration. This code requires a three-dimensional (3D) grid with high resolution in the peripheral plasma region to reproduce the fine plasma structure. The grid generation tool, FLARE, was utilized to create the grid in conjunction with the code developed to arbitrarily set the outer boundary of the peripheral grid. After setting up the 3D grid, we carried out the EMC3-EIRENE calculation successfully for the first time in the Heliotron J\u27s standard configuration. In addition, the convergence of the iterative calculation and the effects of different grid resolutions upon the calculation were investigated. A good numerical convergence was obtained, and the influence of resolution was observed in the electron density in the divertor region