Impurity screening in Ohmic and high confinement (H-mode) plasmas in the Alcator C-Mod tokamak
A series of experiments has been carried out to determine the relative screening of the low recycling gaseous impurities, nitrogen and methane, in Alcator C-Mod tokamak [Phys. Plasmas {bold 1}, 1511 (1994)] discharges. The impurity density in the core plasma is directly proportional to the rate of impurity injection. Screening was found to vary weakly with plasma density but to be markedly dependent on the poloidal position of injection. Detachment of the plasma results in significantly less screening both in Ohmic and in high confinement (H-mode) discharges, particularly when the gas is injected into the divertor or at the inner vessel wall. Evidence of impurity transport from the scrape-off layer into the divertor using bolometry and visible spectroscopy is presented and modeling of the transport using a two-dimensional Monte Carlo code is described. {copyright} {ital 1997 American Institute of Physics.}
- Research Organization:
- Massachusetts Institute of Technology
- DOE Contract Number:
- AC02-78ET51013
- OSTI ID:
- 561127
- Report Number(s):
- CONF-961102--
- Journal Information:
- Physics of Plasmas, Journal Name: Physics of Plasmas Journal Issue: 5 Vol. 4; ISSN PHPAEN; ISSN 1070-664X
- Country of Publication:
- United States
- Language:
- English
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