Edge shear flows and particle transport near the density limit of the HL-2A tokamak

被引：38

作者：

Hong, R. ^{[1
]}

Tynan, G. R. ^{[1
,3
]}

Diamond, P. H. ^{[2
,3
]}

Nie, L. ^{[3
]}

Guo, D. ^{[3
]}

Long, T. ^{[3
]}

Ke, R. ^{[3
,4
]}

Wu, Y. ^{[3
,5
]}

Yuan, B. ^{[3
,5
]}

Xu, M. ^{[3
]}

机构：

[1] Univ Calif San Diego, Energy Res Ctr, La Jolla, CA 92093 USA

[2] Univ Calif San Diego, Ctr Astrophys & Space Sci, La Jolla, CA 92093 USA

[3] Southwestern Inst Phys, Ctr Fus Sci, Chengdu 610041, Sichuan, Peoples R China

[4] Tsinghua Univ, Dept Engn Phys, Beijing 100084, Peoples R China

[5] Univ Sci & Technol China, Sch Phys Sci, Hefei 230026, Anhui, Peoples R China

来源：

NUCLEAR FUSION | 2018年 / 58卷 / 01期

基金：

中国国家自然科学基金;

关键词：

tokamak; turbulent transport; zonal flows; density limit; Langmuir probe; ALCATOR C-MOD; TURBULENCE; DISRUPTIONS; PLASMAS; JET;

D O I：

10.1088/1741-4326/aa9626

中图分类号：

O35 [流体力学]; O53 [等离子体物理学];

学科分类号：

070204 ; 080103 ; 080704 ;

摘要：

Edge shear flow and its effect on regulating turbulent transport have long been suspected to play an important role in plasmas operating near the Greenwald density limit n(G). In this study, equilibrium profiles as well as the turbulent particle flux and Reynolds stress across the separatrix in the HL-2A tokamak are examined as n(G) is approached in ohmic L-mode discharges. As the normalized line-averaged density (n) over bar (e)/n(G) is raised, the shearing rate of the mean poloidal flow omega(sh) drops, and the turbulent drive for the low-frequency zonal flow (the Reynolds power P-Re) collapses. Correspondingly, the turbulent particle transport increases drastically with increasing collision rates. The geodesic acoustic modes (GAMs) gain more energy from the ambient turbulence at higher densities, but have smaller shearing rate than low-frequency zonal flows. The increased density also introduces decreased adiabaticity which not only enhances the particle transport but is also related to reduction in the eddy-tilting and the Reynolds power. Both effects may lead to cooling of edge plasmas and therefore the onset of MHD instabilities that limit the plasma density.

引用

页数：9

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