Effect of the relative shift between the electron density and temperature pedestal position on the pedestal stability in JET-ILW and comparison with JET-C

Nuclear Fushion

article

E. Stefanikova¹  L. Frassinetti¹  S. Saarelma²  A. Loarte³  I. Nunes⁴  L. Garzotti²  P. Lomas²  F. Rimini²  P. Drewelow⁵  U. Kruezi²  B. Lomanowski⁶  E. de la Luna⁷  L. Meneses⁴  M. Peterka⁸  B. Viola^1,10  C. Giroud²  C. Maggi²  JET contributors^1,11 

[1] Division of Fusion Plasma Physics, KTH Royal Institute of Technology;CCFE, Culham Science Centre;ITER Organization;Instituto de Plasmas e Fusao Nuclear;Max-Planck Institute for Plasma Physics;Department of Physics, Centre for Advanced Instrumentation;Laboratorio Nacional de Fusion CIEMAT;Institute of Plasma Physics AS CR;Faculty of Mathematics and Physics, Charles University in Prague;ENEA;EUROfusion Consortium, JET, Culham Science Centre

关键词: JET;    pedestal;    pedestal position;    pedestal stability;    EUROPED;    Thomson scattering;   

DOI  :  10.1088/1741-4326/aab216

来源: Institute of Physics Publishing Ltd.

【 摘 要 】

The electron temperature and density pedestals tend to vary in their relative radial positions, as observed in DIII-D (Beurskenset al2011Phys. Plasmas18056120) and ASDEX Upgrade (Dunneet al2017Plasma Phys. Control. Fusion5914017). This so-called relative shift has an impact on the pedestal magnetohydrodynamic (MHD) stability and hence on the pedestal height (Osborneet al2015Nucl. Fusion55063018). The present work studies the effect of the relative shift on pedestal stability of JET ITER-like wall (JET-ILW) baseline low triangularity ( δ ) unseeded plasmas, and similar JET-C discharges. As shown in this paper, the increase of the pedestal relative shift is correlated with the reduction of the normalized pressure gradient, therefore playing a strong role in pedestal stability. Furthermore, JET-ILW tends to have a larger relative shift compared to JET carbon wall (JET-C), suggesting a possible role of the plasma facing materials in affecting the density profile location. Experimental results are then compared with stability analysis performed in terms of the peeling-ballooning model and with pedestal predictive model EUROPED (Saarelmaet al2017Plasma Phys. Control. Fusion ). Stability analysis is consistent with the experimental findings, showing an improvement of the pedestal stability, when the relative shift is reduced. This has been ascribed mainly to the increase of the edge bootstrap current, and to minor effects related to the increase of the pedestal pressure gradient and narrowing of the pedestal pressure width. Pedestal predictive model EUROPED shows a qualitative agreement with experiment, especially for low values of the relative shift.

【 授权许可】

Unknown