Investigation of Edge Pedestal Profiles in DIII-D

We have previously found [1,2] that, when experimental profiles of $E_r$ and $V_\theta$ and average values of momentum and heat transfer coefficients inferred from experiment were used as input, the radial profiles of $n,T_i$ and $T_e$ in the edge pedestal could be calculated directly from particle, momentum and energy balance requirements. The pedestal structure (localized steep gradient region) was found to result from a combination of an edge peaking in the ion outward $V_r$ caused by the ionization of recycling neutrals and a strong edge peaking in the inward ion $V_{pinch}$ caused by strong edge peaking in $E_r$ and $V_\theta$. There is theoretical evidence that the peaking in $E_r$ and $V_\theta$ may be caused by the peaking in $V_r$, suggesting the ionization of recycling neutrals as the ultimate cause of the edge pedestal structure. We are carrying out further calculations and examinations of the data to investigate this possibility.\par \vspace{0.5em} \noindent [1] W. M. Stacey, Phys. Plasmas, $\bf {11}$, 5487 (2004).\par \noindent [2] W. M. Stacey and R. J. Groebner, Phys. Plasmas, $\bf {12}$, 042504 (2005).