Description: Techniques of dimensional analysis have been applied to deuterium and hydrogen plasmas in DIII-D to test the postulate that the edge particle source plays a role in forming the edge H-mode density profile. These experiments show that the pedestal density scale length is typically a factor of two to three larger in hydrogen plasmas than in deuterium plasmas with dimensionally similar ion parameters. These results are in agreement with the postulate [1,2] that the density scale length is primarily determined by the local particle source, rather than by the shape of a hypothetical particle transport barrier. The electron temperature scale length displays a similar trend, albeit with a weaker density dependence. Thus the pedestal pressure gradient scale length is larger in hydrogen. It is also observed that the frequency of a coherent mode, localized within the pedestal, increases with the local density (i.e. inversely with the local density scale length) irrespective of the working gas species. This frequency is a factor of two lower in a hydrogen discharge than in a dimensionally similar deuterium plasma, a result which cannot be explained solely in terms of plasma physics variables.
Date: July 1, 2002
Creator: MAHDAVI, M.A.; R.J.GROEBNER; LEONARD, A.W.; LUCE, T.C.; McKEE, G.R.; MOYER, R.A. et al.
Item Type: Refine your search to only Article
Partner: UNT Libraries Government Documents Department