Investigation of the origin of neutrals in the main chamber of Alcator C-Mod

被引:43
作者
Lipschultz, B [1 ]
LaBombard, B
Pitcher, CS
Boivin, R
机构
[1] MIT, Plasma Sci & Fus Ctr, Cambridge, MA 02139 USA
[2] Plasma Surface Engn Inc, Toronto, ON M49 1Y5, Canada
关键词
D O I
10.1088/0741-3335/44/6/309
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
A series of experiments arc described which are aimed at quantifying the relative contribution of divertor leakage and radial ion transport on neutral pressures surrounding the core plasma. Evidence is presented implying that cross-field transport competes with, or dominates, parallel transport in such a way that plasma exists far out in the scrape-off layer (SOL) in the shadow of limiters and recycles on main chamber surfaces. The transition from L- to H-mode core confinement does not affect the far SOL characteristics nor the scaling of pressures around the plasma. Variations in magnetic equilibrium are used to vary the divertor pressures independent of the core plasma. Based on the analysis of such experiments using a simple neutral flow model we estimate that neutrals escaping from leaks in the lower (closed) divertor during lower x-point operation contribute a smaller fraction (similar to10-30%) of the midplane pressure than main chamber recycling. The inferred leakage is much larger from the upper (open) divertor during upper x-point operation. Most neutrals escaping from either divertor do not directly travel to the midplane. Instead, they are redirected, most likely by some combination of ionization and/or collisions (elastic, charge exchange).
引用
收藏
页码:733 / 748
页数:16
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