ISSN:
1089-7666
Source:
AIP Digital Archive
Topics:
Physics
Notes:
Carbon impurity ion transport is studied in the Columbia tokamak "HBT'' [Plasma Physics and Controlled Nuclear Fusion Research 1986 (IAEA, Vienna, 1987), Vol. 1, p. 299], using a carbon tipped probe that is inserted into the plasma (ne ≈1–3×1014 cm−3, Te ≈4–10 eV, Bt ≈0.2–0.4 T). Carbon impurity light, mainly the strong lines of CII (4267 A(ring), emitted by the C+ ions) and CIII (4647 A(ring), emitted by the C++ ions), is formed by the ablation or sputtering of plasma ions and by the discharge of the carbon probe itself. The diffusion transport of the carbon ions is modeled by measuring the space- and time-dependent spectral light emission of the carbon ions with a collimated optical beam and photomultiplier. The point of emission can be observed in such a way as to sample regions along and transverse to the toroidal magnetic field. The carbon ion diffusion coefficients are obtained by fitting the data to a diffusion transport model. It is found that the diffusion of the carbon ions is "classical'' and is controlled by the high collisionality of the HBT plasma; the diffusion is a two-dimensional problem and the expected dependence on the charge of the impurity ion is observed.
Type of Medium:
Electronic Resource
URL:
http://dx.doi.org/10.1063/1.859688
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