Approaching detachment in I-mode—response of core confinement and the edge pedestal in the ASDEX Upgrade tokamak. (15th February 2021)

• Record Type: Journal Article
• Authors: Happel, T.; Reinke, M.L.; Silvagni, D.; Bernert, M.; Grover, O.; Hennequin, P.; Hubbard, A.E.; Plank, U.; Trier, E.; Brida, D.; David, P.; Fischer, R.; Gil, L.; Höfler, K.; Manz, P.; McDermott, R.M.; Merle, A.; Stroth, U.; Viezzer, E.; Willensdorfer, M.; the ASDEX Upgrade Team, ; the EUROfusion MST1 Team,
• Is Part Of: Nuclear fusion. Volume 61:Number 3(2021)
• Publication Date: 2021-02-15
• Subjects: I-mode -- detachment -- ELM-free -- nitrogen seeding -- tokamak -- confinement regime; Nuclear fusion -- Periodicals; 621.48405
• DOI: 10.1088/1741-4326/abd7b7
• Languages: English
• ISSNs: 0029-5515

Abstract

Abstract: Experiments on nitrogen assisted divertor detachment in the improved energy confinement mode (I-mode) are reported from the ASDEX Upgrade tokamak. When nitrogen is introduced into the divertor and radiation losses cool the divertor plasma down, a loss of core confinement is observed, concomitant with an increase in low frequency edge fluctuation levels. The loss in confinement can be compensated and the I-mode can be maintained by additional heating power input. Detachment of the inner divertor leg has been observed for the first time in an I-mode discharge. The outer divertor leg remains attached in these experiments. Good energy confinement properties ( H 98 ( y, 2) = 0.9) during the detachment of the inner divertor leg are reported.