Evaluation of spatiotemporal dynamics of pedestal density fluctuations during inter-ELM cycles on DIII-D

We investigate the spatiotemporal dynamics of density fluctuations during the cycles between Edge localized modes (ELMs) and the mechanisms that limit the gradient using the beam-emission spectroscopy (BES) at DIII-D. ELMs are triggered in the H-mode pedestal when the pressure increases to the Peeling-ballooning (PB) instability boundary, leading to an expulsion of particles and heat across the closed flux surfaces. It is predicted that different turbulent modes in the pedestal have various dependencies on parameters such as q₉₅ and profile gradients. Turbulence characteristics are measured between ELMs at different q₉₅ and temperature gradients through varying plasma current and input power (NBI & ECH). Initial time-averaged analysis has shown dramatic changes in density fluctuations characteristics with stronger electron diamagnetic direction propagating modes at higher ECH power and q₉₅. Detailed dynamics of turbulence characteristics in between ELMs are being analyzed. This analysis will provide rich ‘fingerprints’ data to compare with the existing theories and simulations.