DOE OSTI · 2997570
Divertor characterization and access to dissipative divertor conditions in negative triangularity discharges in DIII-D
Abstract
Reduced radial transport, short midplane-to-target parallel connection lengths, and a strong effect of cross-field drifts were responsible for the high densities required for detachment in strong negative triangularity (NT) configurations in DIII-D. Dissipative divertor conditions were achieved in NT discharges at different triangularity, injected power, plasma current, and toroidal field direction. Differences between negative and positive triangularity (PT) discharges are analyzed in this paper to understand the requirements for access to detached divertor conditions: power balance, geometry, radial transport and effect of cross-field particle drifts. Parametric dependencies of access to detachment on plasma current and power flowing into the scrape-off layer remained similar in negative and PT and impurity seeding was observed to reduce the density needed to detach by up to 30% at the expense of core impurity dilution. The impact of triangularity on core-edge integration was tested varying bottom triangularity at fixed top triangularity. The high density needed to detach was not intrinsic to the NT edge as shapes with positive lower triangularity and negative upper triangularity were able to detach at lower upstream densities while maintaining an ELM-free NT edge. Confinement degradation at deeper detachment levels was however observed in all NT shapes, often associated with radiation instabilities.
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Scotti, Filippo [Lawrence Livermore National Laboratory (LLNL), Livermore, CA (United States)] (ORCID:0000000201969919), Marinoni, Alessandro [University of California, San Diego, CA (United States)] (ORCID:0000000310045782), McLean, Adam G. [Lawrence Livermore National Laboratory (LLNL), Livermore, CA (United States)] (ORCID:0000000206974397), Nelson, A. O. [Columbia University, New York, NY (United States)] (ORCID:0000000296121936), Paz-Soldan, Carlos [Columbia University, New York, NY (United States)] (ORCID:0000000150694934), Thome, K. E. [General Atomics, San Diego, CA (United States)] (ORCID:0000000248013922), Zhao, M. [Lawrence Livermore National Laboratory (LLNL), Livermore, CA (United States)] (ORCID:0000000194877644), Allen, S. [Lawrence Livermore National Laboratory (LLNL), Livermore, CA (United States)], Austin, Max [University of Texas, Austin, TX (United States)] (ORCID:0000000200178605), Burke, M. G. [Lawrence Livermore National Laboratory (LLNL), Livermore, CA (United States)] (ORCID:0000000176193724), Bykov, I. [General Atomics, San Diego, CA (United States)] (ORCID:0000000165196081), Chrystal, Colin [General Atomics, San Diego, CA (United States)] (ORCID:0000000330498658), Eldon, David [General Atomics, San Diego, CA (United States)] (ORCID:0000000318950648), Fenstermacher, M. [Lawrence Livermore National Laboratory (LLNL), Livermore, CA (United States)] (ORCID:0000000156357330), Hyatt, A. [General Atomics, San Diego, CA (United States)], Glass, Fenton [General Atomics, San Diego, CA (United States)] (ORCID:0000000311011859), Lasnier, C. J. [Lawrence Livermore National Laboratory (LLNL), Livermore, CA (United States)] (ORCID:0000000271092278), Lore, Jeremy [Oak Ridge National Laboratory (ORNL), Oak Ridge, TN (United States)] (ORCID:000000029192465X), Leonard, A. [General Atomics, San Diego, CA (United States)] (ORCID:0000000193561074), Murphy, Christopher [General Atomics, San Diego, CA (United States)], Osborne, Thomas [General Atomics, San Diego, CA (United States)] (ORCID:0000000326414597), Sauter, O. [École Polytechnique Fédérale de Lausanne (EPFL) (Switzerland)] (ORCID:0000000200996675), Truong, D. [Lawrence Livermore National Laboratory (LLNL), Livermore, CA (United States)] (ORCID:0000000285732539), Wang, Huiqian Q. [General Atomics, San Diego, CA (United States)] (ORCID:0000000319202799), Wilcox, Robert [Oak Ridge National Laboratory (ORNL), Oak Ridge, TN (United States)] (ORCID:0000000313691739). 2025-09-19. Divertor characterization and access to dissipative divertor conditions in negative triangularity discharges in DIII-D. https://doi.org/10.1088/1361-6587%2Fadf881
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