Transport phenomena in the edge of Alcator C-Mod plasmas

被引:78
作者
Terry, JL [1 ]
Basse, NP
Cziegler, I
Greenwald, M
Grulke, O
LaBombard, B
Zweben, SJ
Edlund, EM
Hughes, JW
Lin, L
Lin, Y
Porkolab, M
Sampsell, M
Veto, B
Wukitch, SJ
机构
[1] MIT, Plasma Sci & Fus Ctr, Cambridge, MA 02139 USA
[2] EURATOM, MPI Plasma Phys, Greifswald, Germany
[3] Ernst Moritz Arndt Univ Greifswald, Greifswald, Germany
[4] Princeton Plasma Phys Lab, Princeton, NJ 08543 USA
[5] Univ Texas, Fus Res Ctr, Austin, TX 78712 USA
关键词
D O I
10.1088/0029-5515/45/11/013
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
Two aspects of edge turbulence and transport in Alcator C-Mod are explored. The quasi-coherent mode (QCM), an edge fluctuation present in Enhanced D alpha H-mode plasmas, is examined with regard to its role in the enhanced particle transport found in these plasmas, its in/out asymmetry, its poloidal wave number and its radial width and location. It is shown to play a dominant role in the perpendicular particle transport. The QCM is not observed at the inboard midplane, indicating that its amplitude there is significantly smaller than on the outboard side. The peak amplitude of the QCM is found just inside the separatrix, with a radial width 5 mm, leading to a non-zero amplitude outside the separatrix and qualitatively consistent with its transport enhancement. Also examined are the characteristics of the intermittent convective transport, associated with the larger scale turbulent structures, also called blobs, and typically occurring in the scrape-off-layer (SOL). These turbulent structures are qualitatively similar in L- and H-mode. When their perpendicular extent, occurrence frequencies and magnitudes are compared, it is found that their size is somewhat smaller in ELMfree H-Mode, while their frequency is similar. A clear difference is seen in the magnitude of these turbulent fluctuations in the far SOL, with ELMfree H-mode showing a smaller perturbation there than L-mode. As the Greenwald density limit is approached (n/n(GW) > 0.7), blobs are seen inside the separatrix consistent with the observation that the high cross-field transport region, normally found in the far SOL, penetrates the closed flux surfaces at high n/n(GW).
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页码:1321 / 1327
页数:7
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