Figure-Experimental study of ELM-induced filament structures using the VUV imaging system on EAST

Fig.1 shows the typical characteristics of type I ELMy H mode, that is the ELM frequency increases with heating power. The experimental data are from different diagnostics in EAST.Fig.2 shows the filamentary structure derived from VUV imaging data by subtracted images during one ELM burst.Fig.3 shows how to quantitatively charactrize the spatial structure of the filaments observed by the VUV imaging system, i.e. by introducing two parameters: the poloidal width and pitch angle. The definition of these two parameters are explained in detail in this figure.Fig.4 shows the dependence of the filament poloidal width on heating power and Fig.5 shows the pitch angle of the filament is inversly propotional to the edge safety factor. These data are derived from the VUV imaging data by following the method introduced in this work.