Fusion breakthrough uses inverted D plasma to solve key energy challenge

Researchers at the DIII-D National Fusion Facility in the US have demonstrated a significant breakthrough in nuclear fusion reactor control by using a plasma configuration called “negative triangularity,” where the plasma cross-section is shaped like an inverted “D” with the curved side facing the tokamak’s inner wall. Contrary to previous expectations that this shape would be less stable, experiments in 2023 showed that negative triangularity plasmas can achieve high pressure, density, and current simultaneously while maintaining excellent heat confinement. This configuration also exhibited unexpectedly low levels of plasma instability, which is critical for sustained fusion reactions and reducing damage to reactor walls. A key challenge in tokamak design is managing the heat at the plasma edge to protect the reactor’s interior while keeping the core hot enough for fusion. The negative triangularity approach successfully combined high plasma confinement with “divertor detachment,” a condition that cools the plasma boundary and reduces heat load on material surfaces without triggering instabilities. This integrated solution addresses the core-edge heat management