First Observation of A Fully Detached Divertor with Natural Compatibility with A High Confinement Plasma State for Steady-state Operation

Excellent compatibility of actively controlled full divertor detachment with a high-performance ($\beta_{\mathrm{N\thinspace }}$\textasciitilde 3, $\beta_{\mathrm{p\thinspace }}$\textgreater 2, H$_{\mathrm{98\thinspace }}$\textasciitilde 1.5) core plasma has been achieved, for the first time, in DIII-D high-$\beta_{\mathrm{p}}$ (poloidal beta) plasmas associated with a sustained core internal transport barrier (ITB) and an H-mode edge transport barrier (ETB). Compared to standard H-mode plasmas, the high-$\beta_{\mathrm{p}}$ plasmas exhibit a much wider window of detachment compatible with a high confinement core. With a newly developed detachment control system, coupled with optimized nitrogen impurity seeding, fully detached divertor plasmas were achieved with low plasma temperature (Te\textless 5eV), low particle flux and low heat flux across the entire divertor target plate. It is found that this high-p high confinement plasma scenario enables full divertor detachment at lower density due to long connection length associated with the high edge safety factor, needed for steady-state, and reduced loss power from core to boundary plasma associated with the high confinement. Furthermore, the divertor detachment facilitates the access to an even stronger ITB at large radius with a weakened ETB through self-organized synergy between ITB and ETB, leading to improved high confinement, in contrast to confinement degradation with divertor detachment in standard H-mode. The presence of a large-radius ITB compensates the degradation of ETB by the divertor detachment, while a weak ETB is more prone to an edge regime with natural small edge localized modes. In particular, with neon injection, a long-period no-ELM H-mode phase has been achieved simultaneously with high-performance core and partially detached divertor plasmas. These results demonstrate the possibility of integrating excellent core plasma performance with an efficient divertor solution, an essential step towards steady-state operation of reactor-grade plasmas.