Interaction between Core and Edge in JET ELMy H-Modes with Mixed Type I-II ELMs: Consequences for the Extension of this Regime towards High Plasma Current

In high triangularity (d 0.5) JET ELMy H-modes,with safety factor q95 @ 3 and plasma current Ip 2.5MA,high confinement (H98y @ 1)is achieved with line averaged density of @ 0.95 of the Greenwald density nGR. In those high density plasmas the Type I ELM frequency fELM decreases and Type II ELMs are observed in the inter-ELM period: this regime is called the mixed Type I/II ELMy regime. New experiments have started in JET to study the scaling with plasma current (up to Ip 3.5MA) of the energy confinement of high d ELMy H-modes and the edge operational space of the mixed Type I/II regime. Since d @ 0.5 is not technically possible in JET at 3.5MA, a plasma configuration with reduced triangularity was selected for those experiments.The extension of high density ELMy H-modes to lower n* also requires the higher input power PIN, that will be soon available with the NBI upgrade, as well as the use of ICRH heating (PIN = PNBI + PICRH 25MW). This paper presents the results of experiments carried out to prepare for the extension to high Ip of the high density ELMy H-mode regime:it reports the study of the performance of the new plasma configuration at reduced Ip (2.5MA),and the results of the first experiment at 3MA.
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