Impurity transport in Alcator C-Mod plasmas
- Plasma Fusion Center, Massachusetts Institute of Technology, 175 Albany St., Cambridge, Massachusetts 02139-4307 (United States)
Trace non-recycling impurities have been injected into Alcator C-Mod [I. H. Hutchinson {ital et al.}, Phys. Plasmas {bold 1}, 1511 (1994)] plasmas in order to determine impurity transport coefficients. Subsequent impurity emission has been observed with spatially scanning x-ray and Vacuum Ultra-Violet (VUV) spectrometer systems. Measured time-resolved brightness profiles of helium- and lithium-like transitions have been compared with those calculated from a transport code which includes impurity diffusion and convection in conjunction with an atomic physics package for individual line emission. During Low-Confinement-Mode (L-mode) plasmas, the transport can be characterized by pure diffusion, with coefficients {approximately}5000 cm{sup 2}/s, reflecting the {approximately}20 ms decay in the x-ray and VUV line brightnesses. During High-Confinement-Modes (H-modes), the impurity confinement times are much longer, and the modelling requires that there be a strong inward convection (of order 1000 cm/s) near the plasma edge, with greatly reduced diffusion (of order 100 cm{sup 2}/s), also in the region of the edge transport barrier. These edge values of the transport coefficients during H-mode are qualitatively similar to the neo-classical values. Nitrogen has also been injected, and after the H- to L-mode transition, the inner shell satellite lines of lithium-like nitrogen dominate in intensity the resonance line of helium-like N{sup 5+} in a thin shell near the plasma edge. {copyright} {ital 1997 American Institute of Physics.}
- Research Organization:
- Massachusetts Inst. of Technology (MIT), Cambridge, MA (United States)
- DOE Contract Number:
- AC02-78ET51013
- OSTI ID:
- 561114
- Report Number(s):
- CONF-961102-; ISSN 1070-664X; TRN: 98:000711
- Journal Information:
- Physics of Plasmas, Vol. 4, Issue 5; Conference: Meeting of the Division of Plasma Physics of the American Physical Society, Denver, CO (United States), 11-15 Nov 1996; Other Information: PBD: May 1997
- Country of Publication:
- United States
- Language:
- English
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