Character and Behavior of Pedestal Density Turbulence in Inter-ELM periods of Type-I ELMing DIII-D Discharges*

Changes in character and temporal behavior of electron and ion scale density turbulence going from the foot to the top of the pedestal in type-I inter-ELM periods are reported for H-mode discharges of DIII-D tokamak. ITG-scale (k$_{\mathrm{\theta }}\rho_{\mathrm{s}}$\textasciitilde 0.3) \~{n} near pedestal foot increases just after ELM crash and gradually decreases as inter-ELM period progresses. Amplitude of this ITG scale \~{n} correlates well with the divertor D$\alpha $ light intensity indicating its role in edge particle transport. TEM scale (k$_{\mathrm{\theta }}\rho _{\mathrm{s}}$\textasciitilde 0.7-1.2) \~{n} measured in the steep gradient region of the pedestal shows a critical gradient behavior i.e. increases once a critical pedestal pressure gradient ($\nabla $P$_{\mathrm{e,ped}})$ is reached and its saturation correlates with that of $\nabla $P$_{\mathrm{e,ped}}$. TEM-scale (k$_{\mathrm{\theta }}\rho _{\mathrm{s}}$\textasciitilde 1-2) \~{n} measured around pedestal top has stronger amplitude compared to that in the steep gradient region, consistent with higher ExB shear in the steep gradient region suppressing more of this TEM-scale \~{n}. Adding ECH at $\rho $\textasciitilde 0.5, pedestal density gradient decreases, temperature gradient increases, and ELM frequency increases. Steep gradient localized TEM-scale \~{n} are suppressed and pedestal top TEM-scale \~{n} are unchanged after adding ECH indicating a possible role of \~{n} (in steep gradient region) in determining the inter-ELM period. Understanding these fluctuation behaviors will help gaining predictive capability of H-mode pedestal evolution.