A dependence of carbon impurity transport coefficients on fuel ions in hydrogen and helium plasmas of Large Helical Device

H. Nozato, S. Morita, M. Goto, Y. Takase, A. Ejiri, T. Amano, K. Tanaka, S. Inagaki

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Abstract

Impurity transport of carbon has been studied using a new method combined carbon pellet injection with high-spatial resolution bremsstrahlung measurement on the Large Helical Device [A. Iiyoshi et al., Fusion Technol. 17, 169 (1990)]. The carbon pellets are injected into a steady phase in neutral beam heated discharges with a standard configuration of Rax=3.6 m. The particle transport coefficients (diffusion coefficient D and convective velocity V) are inferred using a diffusive/ convective model. The results are compared between hydrogen and helium plasmas. As a result, it is found that the analyzed D has a constant radial profile with almost closed values of 0.2 m2/s in both plasmas. On the other hand, the inward V is required only at the plasma outer region (ρ>0.6) where the electron density gradient exits, and the inward V in helium plasmas (-0.4 m/s at ρ=0.8 and ne∼4. 0×1019 m-3) is nearly half as much as that in hydrogen plasmas (-0.7 m/s). This difference of the inward V between hydrogen and helium plasmas suggests a dependence on the charge state of fuel ions predicted from neoclassical theory.

Original languageEnglish
Article number092502
JournalPhysics of Plasmas
Volume13
Issue number9
DOIs
Publication statusPublished - Oct 10 2006
Externally publishedYes

All Science Journal Classification (ASJC) codes

  • Condensed Matter Physics

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