Full RMP-Driven ELM Suppression in High-Performance Double Null Plasmas on DIII-D Tokamak

We report the first demonstration of robust, full suppression of ELMs using RMPs in high-performance, near double-null configuration plasmas on DIII-D. Full ELM suppression is achieved across a broad range of dRsep (from 3 cm to 0.2 cm), including highly shaped equilibria with upper/lower triangularities δ~0.95/0.93 at dRsep=0.2 cm, while maintaining excellent confinement (H₉₈ ≈ 1.5, β_N > 2.5) and low pedestal collisionality (ν_*^e < 0.1). Remarkably, full ELM suppression is sustained over an exceptionally wide q₉₅ window (4.1–5.3) and occurs without the density pump-out typically associated with RMPs in ITER-similar shape plasmas. Instead, confinement improves with elevated pedestal density (up to ~4×10¹⁹ m⁻³) and temperature (~2.5 keV). Microwave Scattering measurements reveal a unique turbulence signature during ELM suppression: notable increased magnetic fluctuations were observed accompanied by marginal growth in density fluctuations – opposite to conventional RMP ELM suppression. GPEC modeling attributes the efficacy to a >2x amplified plasma response at β_N ~2.5, driven by high pedestal pressure and low ν_*^e, overcoming the typically reduced RMP effectiveness at high triangularity. ELITE stability analysis confirms the pedestal is located near the peeling boundary throughout. This breakthrough demonstrates the compatibility of RMP-based ELM suppression with reactor-relevant double null geometries and high-confinement scenarios, resolving a critical challenge for future fusion power plants.