Speaker
Wei Chen
Description
See the full Abstract at http://ocs.ciemat.es/EPS2018ABS/pdf/P4.1003.pdf
Kinetic Electromagnetic Instabilities in an ITB Plasma with Weak
Magnetic Shear
W. Chen1 , D.L. Yu1 , R.R. Ma1 , P.W. Shi1 , Y.Y. Li2 , Z.B. Shi1 , H.R. Du3 , X.Q. Ji1 , M. Jiang1 ,
L.M. Yu1 , B.S. Yuan1 , Y.G. Li1 , Z.C. Yang1 , W.L. Zhong1 , Z.Y. Qiu1 , X.T. Ding1 ,J.Q. Dong1 ,
Z.X. Wang3 , J.Y. Cao1 , S.D. Song1 , Yi. Liu1 ,Q.W. Yang1 , M. Xu1 , and X.R. Duan1 ,
1 Southwestern Institute of Physics, P.O. Box 432 Chengdu 610041, China
2 Institute for Fusion Theory and Simulation, Zhejiang Univ., Hangzhou 310027, China
3 Southwest Jiaotong University, Chengdu 610031, China
Internal transport barriers (ITBs) had been observed on almost fusion devices including HL-
2A. ITBs are favored by weak or reversed magnetic shear. As predicted by MHD theory, the
high-n ballooning modes seem to be stabilized in ITB region, but low-n MHD instabilities re-
main a problem. In this talk, we will report experimental results in HL-2A NBI ITB plasmas
with weak magnetic shears (s ∼ 0)and low pressure gradients (α < 0.3). The low-n Alfvenic IT-
G (AITG) instabilities with fBAE < f < fTAE and n = 2 − 8 are found to be unstable in the NBI
plasmas with weak shears and low pressure gradients. The measured results are also consistent
with the extended generalized fishbone-like dispersion relation (GFLDR-E) and KBM equation,
and the modes are more unstable |s| is smaller in low pressure gradient regions. These modes
have possibly opposite effects on the ITB formation. The interaction between AITG/KBM ac-
tivities and EPs should also be investigated with greater attention in fusion plasmas, such as
ITER, since weak magnetic shear amplifies the role of and possible excitation by EP of these
fluctuations. It is worth emphasizing that the study of AITG/KBM should be paid more atten-
tion because they link to the ITB and H-mode pedestal physics for weak magnetic shears. These
results also pave the road to more in depth analysis of similar phenomena in fusion plasmas with
non-perturbative EP populations, with suggestive possibility of controlling plasma performance
by a careful choice of plasma profiles in the weak shear core region typical of burning fusion
plasmas.
