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| Destabilization of low-frequency modes (LFMs) driven by a thermal pressure gradient in EAST plasmas with q(min) <= 2 | |
Xu, Ming1 ; Ma, Ruirui2; Xu, Liqing1; Li, Yingying1,3; Zhao, Hailin1; Chen, Wei2; Wang, Shouxin1; Li, Guoqiang1; Zhong, Guoqiang1; Wang, Fudi1; Jin, Yifei1; Huang, Juan1; Zang, Qing1; Liu, Haiqing1; Hu, Liqun1; Gong, Xianzu1; Xu, Guosheng1; Hu, Jiansheng1; Wan, Baonian1
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| 2022-12-01 | |
| Source Publication | NUCLEAR FUSION
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| ISSN | 0029-5515 |
| Corresponding Author | Ma, Ruirui(rrma@swip.ac.cn) ; Xu, Liqing(lqxu@ipp.ac.cn) |
| Abstract | 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. |
| Keyword | low-frequency mode double tearing mode kinetic ballooning mode thermal pressure gradient |
| DOI | 10.1088/1741-4326/ac9292 |
| WOS Keyword | ALFVEN EIGENMODES ; PREDICTIONS ; EXISTENCE ; PHYSICS |
| Indexed By | SCI |
| Language | 英语 |
| Funding Project | 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] |
| Funding Organization | National Nature Science Foundation of China ; National Magnetic Confinement Fusion Science Program of China |
| WOS Research Area | Physics |
| WOS Subject | Physics, Fluids & Plasmas |
| WOS ID | WOS:000873251300001 |
| Publisher | IOP Publishing Ltd |
| Citation statistics | |
| Document Type | 期刊论文 |
| Identifier | http://ir.hfcas.ac.cn:8080/handle/334002/129864 |
| Collection | 中国科学院合肥物质科学研究院 |
| Corresponding Author | Ma, Ruirui; Xu, Liqing |
| Affiliation | 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 |
| Recommended Citation 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). |
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