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Impact of fine divertor geometrical features on the modelling of JET corner configurations

Abstract : The modelling of JET corner configurations, in which the strike points are positioned deep in the corners of the divertor, is extremely challenging for edge plasma mean-field modelling tools. To circumvent this technical limitation, a geometrical approximation has been proposed, consisting in considering an artificial minor modification of the geometry of the divertor targets plates. In this paper, we investigate how significantly this approximation impacts the output of mean-field simulations. Using the SOLEDGE2D-EIRENE mean-field code which has the unique capability to be able to cope with both the real and the modified geometry, we have performed a density scan in H-mode for pulses in which the outer strike-point lies in the corner of the divertor. We report here how simulations in the artificial geometry differ from the ones in real geometry. At the exception of low density cases, mid-plane profiles in the closed field lines region and the near scrape-off layer are little impacted. Further out however, in flux-surfaces that are concerned by the geometrical modification, we find that modifying the geometry leads to a strong overestimate of the plasma density. The density perturbation is not local and concerns the whole flux surfaces. Although the divertor geometry is modified only on the outer side, the largest impact is found at the inner divertor where densities are systematically overestimated by a factor that can exceed 10 in low density cases in the far SOL and temperature underestimated by 10 to 20eV in most of the studied density range. The near SOL and strike point peak values are also impacted in the same direction with density changes by a factor of 2. As a consequence, the threshold to detachment of the inner divertor is found lower in the approximate geometry than in the real one. Due to the large flux expansion between the outer and the inner target, the difference in plasma is especially sensitive at the top of the inner divertor baffle, which could have consequence on the evaluation of physical sputtering at that critical location.
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Preprints, Working Papers, ...
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https://hal-amu.archives-ouvertes.fr/hal-03667795
Contributor : Yannick Marandet Connect in order to contact the contributor
Submitted on : Friday, May 13, 2022 - 4:01:49 PM
Last modification on : Friday, May 20, 2022 - 3:36:56 AM

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P. Tamain, H. Bufferand, G. Ciraolo, C. Giroud, Y. Marandet, et al.. Impact of fine divertor geometrical features on the modelling of JET corner configurations. 2022. ⟨hal-03667795⟩

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