Effect of plasma shape variation on ELMs and H-mode pedestal properties inASDEX Upgrade

The effect of plasma shape variation (in particular, variation of the upper and lower triangularity delta) on edge localized modes (ELMs) and H-mode p edestal properties in ASDEX Upgrade is reported here. Strongly shaped plasm as (high delta) show an increased edge pressure gradient and, without exter nal gas puff, type-I ELMs generally have larger losses and lower frequency than in plasmas with low delta. With external gas puff; ELM losses at high delta are reduced and in the same range as found for low delta. The average ELM power loss is a constant fraction of the total loss power, independent of triangularity. The width of the steep electron temperature and pressure gradient zone remains essentially constant at low delta while at high delt a it shows a variation inconsistent with a poloidal gyroradius scaling. The edge pressure gradient and the pedestal pressure scales strongly with plas ma current and triangularity. In type-I ELM H-modes, the pedestal pressure is directly related to the global stored plasma energy, independent of plas ma shape.