Destabilization of the internal kink mode by energetic electrons on the HL-2A tokamak

• Published in: Nuclear fusion Vol. 49; no. 7; pp. 075022 - 075022 (6)
• Main Authors: Chen, W, Ding, X.T, Liu, Yi, Yuan, G.L, Zhang, Y.P, Dong, Y.B, Song, X.Y, Zhou, J, Song, X.M, Deng, W, Yang, Q.W, Ji, X.Q, Duan, X.R, Liu, Y
• Format: Journal Article
• Language: English
• Published: Bristol IOP Publishing 01.07.2009; Institute of Physics
• Subjects: Exact sciences and technology; Magnetic confinement and equilibrium; Physics; Physics of gases, plasmas and electric discharges; Physics of plasmas and electric discharges; Plasma heating by microwaves; ecr, lh, collisional heating; Plasma production and heating; Tokamaks; Tokamak; Experimental data; Hard x radiation; Energy distribution; Photodetectors; Velocity distribution; Experimental study; Kink instability; Trapped ions; Trapped electrons; High field; Confined plasma; ECR heating; Electron drift; Plasma heating; Plasma current; Drift velocity; Maxwell distribution; Magnetic shear
• ISSN: 0029-5515; 1741-4326
• DOI: 10.1088/0029-5515/49/7/075022

A strong burst of the internal kink mode has been observed during ECRH on the HL-2A. It has been experimentally identified that the energetic electrons, which deviate from Maxwell velocity distribution, excite the mode, which was a so-called electron fishbone (e-fishbone). The energy distribution of the electrons is indirectly measured by a hard x-ray detector (CdTe) with the pulse height analysis. When the counts of the energetic electrons with 35–70 keV increase to a higher level, the mode can be obviously observed. The e-fishbone can be excited during off-axis ECRH deposited on both the high field side and the low field side. The modes propagate toroidally parallel to the precession velocity of deeply trapped ions which is in the same direction as the plasma current (co-current) and poloidally parallel to the electron diamagnetic drift velocity. In order to further identify with the e-fishbone mode, the resonance condition of the wave–particle has been investigated. Comparing with experimental results, the calculation analyses show that the mode frequency is close to the precession frequency of the barely trapped electrons or barely circulating electrons when the magnetic shear is very weak or negative.