Internal magnetic fluctuations Measurements in Quiescent and ELMy H-mode DIII-D plasmas using Faraday-effect polarimetry

Internal magnetic fluctuations in Quiescent and ELMy H-mode plasmas, which play important roles in plasma transport and confinement, and can be used in model validation, have been measured using a multi-channel Faraday-effect polarimeter on DIII-D. In standard Quiescent H-mode (QH) plasmas, Faraday-effect polarimetry shows that the n=2 edge harmonic-oscillation (EHO) has the largest internal radial magnetic fluctuation (~2 Gauss), in contrast to Mirnov coils that show the n=1 EHO has the largest poloidal magnetic fluctuation. In wide-pedestal QH-mode (WPQH) plasmas with almost zero NBI torque, weakly coherent magnetic fluctuations (1.5-2 Gauss) with large toroidal mode numbers (n>6) are observed in the core region. Broadband magnetic fluctuations are also observed from 150 to 450 kHz and from 70 to 150 kHz, respectively, in both QH and WPQH plasmas. In ELMy H mode plasmas, broadband magnetic fluctuations from 150 to 500 kHz are observed between ELMs with maximum amplitude near the mid-plane. Between ELM events, the magnetic fluctuations increase up to ~15 Gauss and saturate when the pedestal gradient saturates, indicating their role in pedestal transport.