The role of MHD in causing impurity peaking in JET hybrid plasmas. (27th April 2016)

• Record Type: Journal Article
• Authors: Hender, T.C.; Buratti, P.; Casson, F.J.; Alper, B.; Baranov, Yu. F.; Baruzzo, M.; Challis, C.D.; Koechl, F.; Lawson, K.D.; Marchetto, C.; Nave, M.F.F.; Pütterich, T.; Reyes Cortes, S.
• Other Names: collab.
• Is Part Of: Nuclear fusion. Volume 56:Number 6(2016:Jun.)
• Publication Date: 2016-04-27
• Subjects: impurity transport -- MHD instabilities -- hybrid scenario; Nuclear fusion -- Periodicals; 621.48405
• DOI: 10.1088/0029-5515/56/6/066002
• Languages: English
• ISSNs: 0029-5515

Abstract

Abstract: In hybrid plasma operation in JET with its ITER-like wall (JET-ILW) it is found that n > 1 tearing activity can significantly enhance the rate of on-axis peaking of high- Z impurities, which in turn significantly degrades discharge performance. Core n = 1 instabilities can be beneficial in removing impurities from the plasma core (e.g. sawteeth or fishbones), but can conversely also degrade core confinement (particularly in combination with simultaneous n = 3 activity). The nature of magnetohydrodynamic instabilities in JET hybrid discharges, with both its previous carbon wall and subsequent JET-ILW, is surveyed statistically and the character of the instabilities is examined. Possible qualitative models for how the n > 1 islands can enhance the on-axis impurity transport accumulation processes are presented.