Abstract
Novel internal measurements and analysis of ion cyclotron frequency range fast-ion driven modes in DIII-D are presented. Observations, including internal density fluctuation (ñ) measurements obtained via Doppler Backscattering, are presented for modes at low harmonics of the ion cyclotron frequency localized in the edge. The measurements indicate that these waves, identified as coherent Ion Cyclotron Emission (ICE), have high wave number, _⊥ρ_fast ≳ 1, consistent with the cyclotron harmonic wave branch of the magnetoacoustic cyclotron instability (MCI), or electrostatic instability mechanisms. Measurements show extended spatial structure (at least ~ 1/6 the minor radius). These edge ICE modes undergo amplitude modulation correlated with edge localized modes (ELM) that is qualitatively consistent with expectations for ELM-induced fast-ion transport.
Plasma potential enhancement by rf heating near the ion-cyclotron frequency