Robust avoidance of edge-localized modes alongside gradient formation in the negative triangularity tokamak edge

Abstract

In a series of high performance diverted discharges on DIII-D, we demonstrate that strong negative triangularity (NT) shaping robustly suppresses all edge-localized mode (ELM) activity over a wide range of plasma conditions: $⟨n⟩=0.1-1.5\times 10^{20}$m${}^{-3}$, $P_{\mathrm{aux}}=0-15$MW and $|B_{\mathrm{t}}|=1-2.2$T, corresponding to $P_{\mathrm{loss}}/P_{LH08}\sim 8$. The full dataset is consistent with the theoretical prediction that magnetic shear in the NT edge inhibits access to ELMing H-mode regimes; all experimental pressure profiles are found to be at or below the infinite-$n$ ballooning stability limit. Importantly, we also report enhanced edge pressure gradients at strong NT that are significantly steeper than in traditional ELM-free L-mode plasmas and provide significant promise for NT reactor integration.

5 pages, 5 figures

References in corpus (3)

• H-mode inhibition in negative triangularity tokamak reactor plasmas
• Plasma Performance and Operational Space without ELMs in DIII-D
• Radiative pulsed L-mode operation in ARC-class reactors

Cited by in corpus (6)

• Simultaneous access to high normalized current, pressure, density, and confinement in strongly-shaped diverted negative triangularity plasmas
• Kinetic-Ballooning-Bifurcation in Tokamak Pedestals Across Shaping and Aspect-Ratio
• Validation of NSFsim as a Grad-Shafranov Equilibrium Solver at DIII-D
• Assessing the Numerical Stability of Physics Models to Equilibrium Variation through Database Comparisons
• On the feasibility of Ohmically heated negative triangularity tokamak power plants
• Disentangling Core and Edge Mechanisms of the Density Limit in DIII-D Negative Triangularity Plasmas