Dynamics of electron internal transport barrier formation at the H–L transition on EAST. (1st June 2022)

• Record Type: Journal Article
• Authors: Han, X.; Liu, Y.; Zhou, T.F.; Zhang, T.; Shi, T.H.; Li, Y.Y.; Yuan, Y.; Mao, S.T.; Jin, Y.F.; Wu, X.H.; Wang, S.X.; Yang, Y.; Wen, F.; Huang, J.; Liu, S.C.; Ye, K.X.; Wu, M.F.; Geng, K.N.; Li, G.S.; Zhong, F.B.; Xiang, H.M.; Gao, X.; the EAST Team,
• Is Part Of: Nuclear fusion. Volume 62:Number 6(2022)
• Publication Date: 2022-06-01
• Subjects: internal transport barrier -- RSAEs -- H–L transition -- EAST; Nuclear fusion -- Periodicals; 621.48405
• DOI: 10.1088/1741-4326/ac5c75
• Languages: English
• ISSNs: 0029-5515

Abstract

Abstract: The dynamics of electron-internal transport barrier (e-ITB) formation is studied in the hybrid plasma of neutral beam injection and lower hybrid wave heating on EAST. The e-ITB is observed to be repetitively formed at the H–L transition, where the relaxation process of core radiation triggers an increase in neutron yield and core electron temperature. A reversed q -profile is beneficial for generating the barrier, identified by the appearance of reversed shear Alfvén eigenmodes (RSAEs). The dimensionless parameter of the normalized Larmor radius ( ρ T e * ) is estimated to visualize the dynamic behavior of the e-ITB. It is found that the e-ITB forms once the electron ρ T e * exceeds 0.014, and the RSAEs are accompanied by the e-ITB formation. The barrier foot moves inwards until the L–H transition occurs, where the H-mode pedestal or type-I edge localized mode (ELM) strongly influences the e-ITB intensity. The results of thermal transport modeling show a significant reduction in the core thermal transport coefficient in the electron channel while maintaining a nearly unchanged ion transport level as the e-ITB evolves.