The two-dimensional structure of radiative divertor plasmas in the DIII-D tokamak
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- Lawrence Livermore National Laboratory, P.O. Box 808, Livermore, California 94550 (United States)
Recent measurements of the two-dimensional (2-D) spatial profiles of divertor plasma density, temperature, and emissivity in the DIII-D tokamak [J. Luxon {ital et al.}, in {ital Proceedings of the 11th International Conference on Plasma Physics and Controlled Nuclear Fusion} (International Atomic Energy Agency, Vienna, 1987), p. 159] under highly radiating conditions are presented. Data are obtained using a divertor Thomson scattering system and other diagnostics optimized for measuring the high electron densities and low temperatures in these detached divertor plasmas (n{sub e}{le}10{sup 21}m{sup {minus}3}, 0.5eV{le}T{sub e}). D{sub 2} gas injection in the divertor increases the plasma radiation and lowers T{sub e} to less than 2 eV in most of the divertor volume. Modeling shows that this temperature is low enough to allow ion{endash}neutral collisions, charge exchange, and volume recombination to play significant roles in reducing the plasma pressure along the magnetic separatrix by a factor of 3{endash}5, consistent with the measurements. Absolutely calibrated vacuum ultraviolet spectroscopy and 2-D images of impurity emission show that carbon radiation near the X-point, and deuterium radiation near the target plates contribute to the reduction in T{sub e}. Uniformity of radiated power (P{sub rad}) (within a factor of 2) along the outer divertor leg, with peak heat flux on the divertor target reduced fourfold, was obtained. A comparison with 2-D fluid simulations shows good agreement when physical sputtering and an {ital ad hoc} chemical sputtering source (0.5{percent}) from the private flux region surface are used. {copyright} {ital 1997 American Institute of Physics.}
- Research Organization:
- General Atomics
- DOE Contract Number:
- AC03-89ER51114; AC04-94AL85000; AC05-96OR22464; W-7405-ENG-48
- OSTI ID:
- 560616
- 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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