Development of an integrated core–edge scenario using the super H-mode

• Published in: Nuclear fusion 2021-12, Vol.61 (12), p.126064
• Main Authors: Wilks, T.M., Knolker, M., Snyder, P.B., Eldon, D., Scotti, F., Chrystal, C., Laggner, F.M., Lasnier, C., Mclean, A., Osborne, T., Paz-Soldan, C., Wang, H., Watkins, J., Casali, L., Grierson, B., Hughes, J.W.
• Format: Article
• Language: English
• Subjects: 70 PLASMA PHYSICS AND FUSION TECHNOLOGY; core–edge integration; divertor; pedestal; super H-mode; tokamak
• ISSN: 0029-5515; 1741-4326
• DOI: 10.1088/1741-4326/ac34d6

An optimized pedestal regime called the super-H (SH) mode is leveraged to couple a fusion relevant core plasma with a high density scrape-off layer appropriate for realistic reactor power exhaust solutions. Recent DIII-D experiments have expanded the operating space of the SH regime using advanced control algorithms and investigated optimization of impurity seeding, deuterium gas puffing, and 3D magnetic perturbations. Simultaneous real-time control of the pedestal density and radiated power with in-vessel coils and nitrogen seeding enable optimal coupled divertor and pedestal conditions. Four case studies are analysed with varied levels of radiated power in the divertor volume ranging from 0 (no seeding) to 8.5 MW radiated from carbon and nitrogen emission. Plasmas with a 4.5 MW radiated power target establish a radiative mantle, leading to divertor temperatures of ∼16 eV while maintaining SH-mode, and with only marginal impact on the pedestal and core performance. Increased levels of N 2 seeding with a 7.5 MW radiated power target facilitate detachment onset and divertor temperatures 2.5 τ E . Finally, a 8.5 MW radiated power target leads to partial detachment, which is so far associated with the loss of access to SH-mode pedestal conditions.