Dependence of H-mode pedestal parameters on plasma magnetic geometry

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Abstract
The dependence of the edge pedestal electron pressure on magnetic geometry is studied using the international pedestal database. For type I ELM discharges, the pressure normalized to B2 is found to scale roughly inversely with major radius and inverse aspect ratio. In addition, a strong increase in pressure with increasing shape is found when the pressure is normalized to a ballooning type scaling. Ballooning stability calculations suggest that there is significant variation in the normalized edge pressure gradient in the database. The observed shape dependence reflects this variation, although the applicability of the log-linear type dependences used here must be in question if phase changes such as from first to second stability are spanned by the data. This question can only be resolved by upgrading the database to include edge pressure profiles, or fits to profiles, rather than only pedestal-top values.