Robust Avoidance of Edge-Localized Modes alongside Gradient Formation in the Negative Triangularity Tokamak Edge

Nelson, A. O.; Schmitz, L. (ORCID:0000000313460914); Paz-Soldan, C. (ORCID:0000000150694934); Thome, K. E. (ORCID:0000000248013922); Cote, T. B.; Leuthold, N.; Scotti, F.; Austin, M. E. (ORCID:0000000200178605); Hyatt, A. (ORCID:0000000333845280); Osborne, T. (ORCID:0000000326414597)

doi:10.1103/physrevlett.131.195101

DOE OSTI · 2008488

Robust Avoidance of Edge-Localized Modes alongside Gradient Formation in the Negative Triangularity Tokamak Edge

Nelson, A. O.·Schmitz, L. (ORCID:0000000313460914)·Paz-Soldan, C. (ORCID:0000000150694934)·Thome, K. E. (ORCID:0000000248013922)·Cote, T. B.·Leuthold, N.·Scotti, F.·Austin, M. E. (ORCID:0000000200178605)·Hyatt, A. (ORCID:0000000333845280)·Osborne, T. (ORCID:0000000326414597)

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Abstract

In a series of high performance diverted discharges on DIII-D, we demonstrate that strong negative triangularity (NT) shaping robustly suppresses all edge-localized mode (ELM) activity over a wide range of plasma conditions: ⟨n⟩ = 0.1 − 1.5 × 1020 m−3, Paux = 0 − 15 MW and |Bt| = 1 − 2.2 T, corresponding to Ploss/PLH08 ∼ 8. The full dataset is consistent with the theoretical prediction that magnetic shear in the NT edge inhibits access to ELMing H-mode regimes; all experimental pressure profiles are found to be at or below the infinite-n ballooning stability limit. Our present dataset also features edge pressure gradients in strong NT that are closer to an H–mode than a typical L-mode plasma, supporting the consideration of NT for reactor design.

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Nelson, A. O., Schmitz, L. (ORCID:0000000313460914), Paz-Soldan, C. (ORCID:0000000150694934), Thome, K. E. (ORCID:0000000248013922), Cote, T. B., Leuthold, N., Scotti, F., Austin, M. E. (ORCID:0000000200178605), Hyatt, A. (ORCID:0000000333845280), Osborne, T. (ORCID:0000000326414597). 2023-11-08. Robust Avoidance of Edge-Localized Modes alongside Gradient Formation in the Negative Triangularity Tokamak Edge. https://doi.org/10.1103/physrevlett.131.195101

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