Parametrisation of target heat flux distribution and study of transport parameters for boundary modelling in W7-X

Bold, David; Reimold, F.; Niemann, H.; Gao, Yu; Jakubowski, M.; Killer, C.; Winters, V.

doi:10.1088/1741-4326/ac7e2f

Cited by 5 publications

(3 citation statements)

References 39 publications

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“…This range of values is somewhat lower than the v E,θ > 130 m s −1 estimate inferred from the stagnation point shift in CIS images. Several other estimates of v E,θ are above this range: transport modeling using heat flux width measurements and EMC3-Eirene gives v E,θ > 300 m s −1 [51]; measurements of the radial T e,divertor gradient using Langmuir probes imply v E,θ is several kilometers per second [15]; and poloidal velocities measured in the PFR using an array of fluctuation probes range from several hundred meters per second up to 1 km s −1 [15]. More detailed modeling and measurements will be needed to understand these discrepancies and is left as future work.…”

Section: Asymmetry Scaling With Densitymentioning

confidence: 97%

Effects of drifts on scrape-off layer transport in W7-X

et al. 2023

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Drifts affect particle, momentum, and energy transport in the scrape-off layer (SOL) of tokamaks and stellarators, altering plasma flows and creating asymmetries between divertors. To understand how drifts affect SOL transport in the W7-X island divertor, an experiment was performed to compare plasmas with matched core parameters but opposite magnetic field directions, and therefore opposite drift transport directions. Parallel flow measurements made with coherence imaging spectroscopy are interpreted with the aid of a diagnostic forward model and a 1D simple SOL model that includes the E × B drift. In low-density plasmas (n e < 2 × 1019 m−3), the poloidal E × B drift induces a large poloidal density asymmetry within the island SOL, as measured by divertor Langmuir probes. This in turn causes the parallel flow stagnation point to shift from the position halfway between targets to the X-point in the drift direction, leading to near-unidirectional flow throughout the SOL. As density increases, the effects of the poloidal E × B drift decrease substantially, resulting in a smaller density asymmetry and the development of a counter-streaming flow pattern. For the entire density range probed in this experiment (n e = 1.5–6 × 1019 m−3), the experimental observations are more consistent with the effects of the poloidal E × B drift than the radial E × B drift.

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Section: Asymmetry Scaling With Densitymentioning

confidence: 97%

Effects of drifts on scrape-off layer transport in W7-X

et al. 2023

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“…Therefore, the density at the separatrix is assumed to be 1 3 of the line-averaged density. From [30] it can be concluded that this assumption is reasonable for W7-X. In future work, a comparison with densities measured by the Thomson Scattering system from W7-X is foreseen [31].…”

Section: Simulation Setupmentioning

confidence: 82%

“…All anomalous transport coefficients are taken from [10]. Bold et al [30] indicates that it is difficult to obtain quantitative agreement between simulations and experiments for all measured plasma and neutral quantities. However, Feng et al [25] indicates that the global trends can be captured well by EMC3-EIRENE even when full agreement with experimental data is not achieved.…”

Section: Simulation Setupmentioning

confidence: 99%

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

Boeyaert,

Feng,

Frerichs

et al. 2023

Plasma Phys. Control. Fusion

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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.

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Development of a compact bolometer camera concept for investigation of radiation asymmetries at Wendelstein 7-X

Partesotti,

Reimold,

Ruhnau

et al. 2024

Review of Scientific Instruments

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Power exhaust is one of the central challenges in magnetically confined fusion plasmas. Radiative detachment can be employed to reduce particle and heat fluxes to the divertor target, mitigating divertor damage and erosion. However, accomplishing this for a non-axisymmetric machine such as Wendelstein 7-X is a non-trivial task because of the complex role of transport and plasma-wall interaction in a three-dimensional magnetic field topology. We introduce a new bolometer camera design that can be easily installed in multiple toroidal locations and adapted to the required geometry, providing additional spatial coverage. This can be used to locally enhance tomographic capabilities or to resolve spatial variations of the plasma emissivity. By including these non-uniformities in the total radiated power estimate, global power balance measurements can be improved. We model each bolometer camera using ray tracing. We then analyze the forward-modeled detector response to several physically motivated synthetic emission phantoms with respect to its capability to quantify the local average emissivity. The results prove this concept as a promising asset for the investigation of poloidal and toroidal radiated power asymmetries in Wendelstein 7-X. The first CBC prototypes have undergone development and installation for the next experimental campaign.

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Parametrisation of target heat flux distribution and study of transport parameters for boundary modelling in W7-X

Cited by 5 publications

References 39 publications

Effects of drifts on scrape-off layer transport in W7-X

Effects of drifts on scrape-off layer transport in W7-X

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

Development of a compact bolometer camera concept for investigation of radiation asymmetries at Wendelstein 7-X

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