High confinement in negative triangularity discharges in DIII-D

Discharges with negative triangularity ($\delta )$ shape have been created in DIII-D with H-mode-like confinement (H$_{\mathrm{98y2}} \quad =$ 1.2) and high normalized beta (\textit{{\ss}}$_{\mathrm{N}} \quad =$ 2.6) with L-mode-like edge pressure profiles and no ELMs. These inner-wall-limited plasmas with $\delta =$\textit{-0.4 }had the same global performance as a positive triangularity ($\delta =$\textit{0.4)} ELMing H-mode discharge with the same $I_{\mathrm{p}}$, elongation and area. Preliminary fluctuation data shows negative $\delta $ plasmas have lower turbulence levels, typically reduced by 20{\%}, in the outer region of the plasma, 0.7 \textless $r/a $\textless 1.0, compared to equivalent positive $\delta $ discharges. Correspondingly, transport analysis indicates reduced ion and electron diffusivities for negative $\delta $ compared to the positive $\delta $ cases. Also, the positive triangularity discharges had 30-50{\%} lower neutron rates as the identically heated negative triangularity ones, due primarily to impurity retention and deuterium dilution. These results show that negative triangularity is a viable candidate for reactor scenarios with its high confinement, ELM-mitigated characteristics plus a more economical and effective option for divertor placement.