Destabilization of low-frequency modes (LFMs) driven by a thermal pressure gradient in EAST plasmas with q(min) <= 2

doi:10.1088/1741-4326/ac9292

	Destabilization of low-frequency modes (LFMs) driven by a thermal pressure gradient in EAST plasmas with q(min) <= 2
	Xu, Ming 1; Ma, Ruirui 2; Xu, Liqing 1; Li, Yingying 1,3; Zhao, Hailin 1; Chen, Wei 2; Wang, Shouxin 1; Li, Guoqiang 1; Zhong, Guoqiang 1; Wang, Fudi 1
刊名	NUCLEAR FUSION
	2022-12-01
卷号	62
关键词	low-frequency mode double tearing mode kinetic ballooning mode thermal pressure gradient
ISSN号	0029-5515
DOI	10.1088/1741-4326/ac9292
通讯作者	Ma, Ruirui(rrma@swip.ac.cn) ; Xu, Liqing(lqxu@ipp.ac.cn)
英文摘要	Mode structures and excitation conditions for the low-frequency modes (LFMs) have been investigated in experimental advanced superconducting tokamak (EAST) plasmas with q(min) <= 2. Two different stages/categories of the LFM instabilities are observed during the oscillation of annular/central collapse events: (I) the upward sweeping frequency of LFMs; (II) the upward frequency jumpsof LFMs. The annular/central events are triggered by the m/n = 2/1 double tearing modes with different q-profiles, while the LFMs are characterized by higher mode numbers m/n = 4/2, 6/3, ..., where m and n are the poloidal and toroidal mode numbers, respectively. The maximum radial coverage of the LFMs is located in the annular region of 1.97 <= R <= 2.07 m with the normalized minor radius 0.2 <= rho <= 0.4, while the higher-frequency (or upward sweeping frequency) branch is more localized to the radial position of 2 <= R <= 2.02 m (q(min)). The frequency characteristics of upward sweeps or upward jumps of the LFMs are mainly attributed to the change in the q-profile, e.g. the upward sweeping frequency in stage I is caused by q(min) decreasing. Accordingly, the linear wave properties of LFMs in EAST with weak/reversed magnetic shear are studied numerically and analytically based on a general fishbone-like dispersion relation. Without considering the contribution of energetic ions, it is shown that the LFM with Alfvenic polarization is an MHD-unstable kinetic ballooning mode with frequency of the order of the ion diamagnetic drift frequency. Several important factors for the excitation of LFM instability are analyzed: (1) the role of energetic ions is unimportant, and the LFMs can be excited under the two conditions of with/without energetic ions; (2) the higher tau = T-e/T-i with larger eta(i) = L-ni/L-Ti are required, namely the normalized pressure gradient alpha proportional to (1 + tau)(1 + eta(i)) should be large enough to overcome the stability effect of finite field line bending; (3) the weak/reversed shear q-profile with q(min) <= 2 and suitable S (r/q)(q '')(1/2) are required.
资助项目	National Nature Science Foundation of China[12175271] ; National Nature Science Foundation of China[12175053] ; National Nature Science Foundation of China[11975267] ; National Magnetic Confinement Fusion Science Program of China[2019YFE03020000] ; National Magnetic Confinement Fusion Science Program of China[2018YFE0304100]
WOS关键词	ALFVEN EIGENMODES ; PREDICTIONS ; EXISTENCE ; PHYSICS
WOS研究方向	Physics
语种	英语
出版者	IOP Publishing Ltd
WOS记录号	WOS:000873251300001
资助机构	National Nature Science Foundation of China ; National Magnetic Confinement Fusion Science Program of China
内容类型	期刊论文
源URL	[http://ir.hfcas.ac.cn:8080/handle/334002/129863]
专题	中国科学院合肥物质科学研究院
通讯作者	Ma, Ruirui; Xu, Liqing
作者单位	1.Chinese Acad Sci ASIPP, Inst Plasma Phys, Hefei 230031, Peoples R China 2.Southwestern Inst Phys SWIP, Chengdu 610041, Peoples R China 3.Hebei Key Lab Compact Fus, Langfang 065001, Peoples R China
推荐引用方式 GB/T 7714	Xu, Ming,Ma, Ruirui,Xu, Liqing,et al. Destabilization of low-frequency modes (LFMs) driven by a thermal pressure gradient in EAST plasmas with q(min) <= 2[J]. NUCLEAR FUSION,2022,62.
APA	Xu, Ming.,Ma, Ruirui.,Xu, Liqing.,Li, Yingying.,Zhao, Hailin.,...&Wan, Baonian.(2022).Destabilization of low-frequency modes (LFMs) driven by a thermal pressure gradient in EAST plasmas with q(min) <= 2.NUCLEAR FUSION,62.
MLA	Xu, Ming,et al."Destabilization of low-frequency modes (LFMs) driven by a thermal pressure gradient in EAST plasmas with q(min) <= 2".NUCLEAR FUSION 62(2022).