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arXiv · 2305.13458

Robust avoidance of edge-localized modes alongside gradient formation in the negative triangularity tokamak edge

A. O. Nelson·L. Schmitz·C. Paz-Soldan·K. E. Thome·T. B. Cote·N. Leuthold·F. Scotti·M. E. Austin·A. Hyatt·T. Osborne
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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: $\langle n\rangle=0.1-1.5\times10^{20}$m$^{-3}$, $P_\mathrm{aux}=0-15$MW and $|B_\mathrm{t}|=1-2.2$T, corresponding to $P_\mathrm{loss}/P_\mathrm{LH08}\sim8$. 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. Importantly, we also report enhanced edge pressure gradients at strong NT that are significantly steeper than in traditional ELM-free L-mode plasmas and provide significant promise for NT reactor integration.

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A. O. Nelson, L. Schmitz, C. Paz-Soldan, K. E. Thome, T. B. Cote, N. Leuthold, F. Scotti, M. E. Austin, A. Hyatt, T. Osborne. 2023-05-22. 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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