Impurity transport model for the normal confinement and high density H-mode discharges in Wendelstein 7-AS

K. Ida, R. Burhenn, K. McCormick, E. Pasch, H. Yamada, M. Yoshinuma, S. Inagaki, S. Murakami, M. Osakabe, Y. Liang, R. Brakel, H. Ehmler, L. Giannone, P. Grigull, J. P. Knauer, H. Maassberg, A. Weller

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14 Citations (Scopus)

Abstract

An impurity transport model based on diffusivity and the radial convective velocity is proposed as a first approach to explain the differences in the time evolution of Al XII (0.776 nm), Al XI (55 nm) and Al X (33.3 nm) lines following Al-injection by laser blow-off between normal confinement discharges and high density H-mode (HDH) discharges. Both discharge types are in the collisional regime for impurities (central electron temperature is 0.4 keV and central density exceeds 1020 m-3). In this model, the radial convective velocity is assumed to be determined by the radial electric field, as derived from the pressure gradient. The diffusivity coefficient is chosen to be constant in the plasma core but is significantly larger in the edge region, where it counteracts the high local values of the inward convective velocity. Under these conditions, the faster decay of aluminium in HDH discharges can be explained by the smaller negative electric field in the bulk plasma, and correspondingly smaller inward convective velocity, due to flattening of the density profiles.

Original languageEnglish
Pages (from-to)1931-1938
Number of pages8
JournalPlasma Physics and Controlled Fusion
Volume45
Issue number10
DOIs
Publication statusPublished - Oct 1 2003
Externally publishedYes

All Science Journal Classification (ASJC) codes

  • Nuclear Energy and Engineering
  • Condensed Matter Physics

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