Current and Future Research on Negative Triangularity on the DIII-D Tokamak*

The results of the 2023 DIII-D Negative Triangularity (NT) Campaign are promising for a fusion pilot plant due to its core-edge integration potential. During the campaign, high confinement (H_98y,2≥1), high current (I_p=1.0 MA, q₉₅<3), and high normalized pressure plasmas (β_N>2.5), with short impurity confinement times were achieved at high-injected-power in strongly NT-shaped non-ELMing diverted plasmas over a wide operational space. New detailed physics results from this campaign will be presented, such as: the identification of an edge localized MHD mode, “advanced tokamak” studies at higher q_min, and operation at high core radiated fraction. During the 2023 campaign, the plasma control restricted NT plasma shapes, preventing robust operation at reduced δ_avg and constraining changes to other shaping parameters. Thus, current experimental research at DIII-D is focused on improving NT plasma shape control to address those issues. Also, in the campaign, a detached divertor without impurity seeding was achieved but this required very high density where confinement degradation was observed due to formation of a MARFE.  Ongoing edge modeling work is analyzing the campaign data in preparation for the possible future installation of a new NT divertor.