US team's fusion plasma heat control method to protect tokamak walls

Researchers at the DIII-D National Fusion Facility have developed a novel method to control destructive energy bursts, known as Edge-Localized Modes (ELMs), which threaten the structural integrity of tokamak fusion reactors. By precisely managing the plasma density in the scrape-off-layer (SOL)—the outermost plasma region interacting with the reactor walls—the team demonstrated suppression of large, damaging instabilities while preserving the high-performance core essential for energy production. This approach addresses the critical challenge of core-edge integration, balancing a hot fusion core with a stable edge to prevent damage to reactor components. Using advanced BOUT++ simulations, the researchers uncovered that increasing SOL density fundamentally alters plasma behavior, stabilizing the large-scale "peeling-ballooning modes" responsible for severe ELMs. Instead of infrequent, massive bursts, the plasma exhibits frequent, small, benign energy pulses that induce harmless turbulence, thereby protecting the reactor walls without compromising core pressure or efficiency. Experimental validation confirmed that shaping the SOL density profile can reliably maintain this