Observation of toroidal Alfvén eigenmode excited by energetic electrons induced by static magnetic perturbations in the EAST tokamak. (22nd August 2018)

• Record Type: Journal Article
• Authors: Chu, N.; Sun, Y.; Gu, S.; Wang, H.H.; Hu, Y.J.; Shi, T.H.; Chen, D.L.; Gu, X.; He, K.Y.; Jia, M.; Lin, S.Y.; Liu, H.Q.; Qian, J.P.; Ren, J.; Shen, B.; Ti, A.; Wang, S.X.; Xie, J.L.; Xu, M.; Xue, M.M.; Yan, N.; Zang, Q.; Zeng, L.; Zhang, J.Z.; Zhang, T.; Zhang, Y.; Zhong, G.Q.; Zhou, C.; Zhou, R.J.
• Is Part Of: Nuclear fusion. Volume 58:Number 10(2018:Oct.)
• Publication Date: 2018-08-22
• Subjects: magnetic perturbation -- toroidal Alfvén eignenmode -- reconnection -- magnetic island -- energetic electron; Nuclear fusion -- Periodicals; 621.48405
• DOI: 10.1088/1741-4326/aad70c
• Languages: English
• ISSNs: 0029-5515

Abstract

Abstract: A toroidal Alfvén eigenmode (TAE) excited by barely trapped energetic electrons during the application of a static magnetic perturbations (MPs) is observed for the first time in tokamak ohmic heating plasmas. This TAE appears when the current of a static n = 2 MPs exceeds a threshold value, at which a forced n = 2 magnetic reconnection happens. Here, n is the toroidal mode number. This TAE is located near the plasma edge, which agrees with the calculation of the TAE gap. It propagates in the ion diamagnetic direction and has a dominant toroidal mode number n = 2. The frequency of the TAE is consistent with the precessional frequency of the barely trapped energetic electrons with energy around 150 keV. An increase of the hard x-ray emission intensity in this energy range is observed just after the n = 2 magnetic reconnection. The energetic electrons may be accelerated by the magnetic islands formed after reconnection. The TAE is stabilized after a reduction in the contents of energetic electrons. This observation suggests that the application of static MPs may provide us with a novel method to actively control Alfvén eigenmodes in fusion plasmas.