H Mode Pedestal Characteristics And Mhd Stability Of The Edge Plasma In Alcator C Mod

Under most operational conditions of Alcator C-Mod the dominant type of H-mode is the steady state enhanced Da mode (EDA), characterized by good energy confinement, continuously degraded impurity confinement and absence of regular ELMs. In this regime a quasicoherent (QC) electromagnetic mode ... is observed, localized in the region of the density pedestal. Experimental evidence suggests that the mode is responsible for enhancement of particle transport. It is shown experimentally that the QC mode can exist in a well defined region in edge temperature-safety factor space, favoring high edge q values ... and requiring moderate pedestal temperatureTeped ... As edge temperature and pressure gradient increase, the quasicoherent mode is replaced by broadband low frequency fluctuations (f