Compatibility of divertor detachment and ELM suppression in DIII-D high- βp plasmas with ITER-similar shape

Abstract

Integration of transient and steady-state divertor heat fluxes control with a high-performance core is necessary for future fusion reactors. In recent DIII-D high- βp experiments, divertor detachment and simultaneous edge localized mode (ELM) suppression are demonstrated while the plasma confinement quality is maintained high in ITER-similar shape. By optimizing the neon injection in high- βp scenario with ITER-similar shape, deep detachment and ELM suppression are achieved with a high-performance core ( βN ∼ 2.8, βp ∼ 2.3) at q95 ∼ 7.5. Partial divertor detachment and suppression of large ELMs are achieved at q95 ∼ 6. The stability analyses suggest that with low neon injection, the density pedestal becomes higher and steeper and the Ti profile also increases, therefore the increased edge pressure and higher current density destabilize the Peeling-Ballooning mode (PBM), which would lead to a large ELM collapse. With strong neon gas puffing, the significantly reduced pedestal pressure and current density, due to the degraded Te pedestal, lead to the stabilization of PBM and ELMs are suppressed. For both cases, the coupling between the large radius internal transport barrier (ITB) and edge pedestal is the key reason for maintaining high global performance. The formation of large radius ITB compensates for pedestal degradation. Such results could provide an attractive scenario to well control the transient and steady-state heat flux onto the divertor plates while maintaining good plasma performance, which is an important step toward the steady-state operation of future fusion reactors.