Microstability of β ~ 1 tokamak equilibria

Gaur, Rahul; Abel, Ian G.; Dickinson, David; Dorland, William D.

doi:10.1017/s0022377823000107

Microstability of β ~ 1 tokamak equilibria

Journal Article · Wed Mar 01 04:00:00 EST 2023 · Journal of Plasma Physics

DOI:https://doi.org/10.1017/s0022377823000107· OSTI ID:1991761

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University of Maryland, College Park, MD (United States); University of Maryland
University of Maryland, College Park, MD (United States)
University of York (United Kingdom)

High-power-density tokamaks offer a potential solution to design cost-effective fusion devices. One way to achieve high power density is to operate at a high β value (the ratio of thermal to magnetic pressure), i.e. β~1 . However, a β~1 state may be unstable to various pressure- and current-driven instabilities or have unfavourable microstability properties. To explore these possibilities, we generate β~1 equilibria and investigate their stability. First, we demonstrate the generation of high-β equilibria with the computer code VMEC. We then analyse these equilibria to determine their stability against the infinite-n ideal-ballooning mode. We follow that by engaging in a detailed microstability study using the GS2 code, beginning with assessments of electrostatic ion-temperature-gradient and trapped election mode instabilities. We observe interesting behaviour for the high-β equilibria – stabilization of these modes through two distinct mechanisms – large negative local shear and reversal of electron precession drift. Finally, we perform electromagnetic gyrokinetic simulations and observe enhanced stability in the outer core of high-β equilibria and absence of kinetic ballooning modes in the negative-triangularity, high-β equilibria. The enhanced outer-core stability of high-β equilibria is different from their lower-β counterparts and offers an alternative, potentially favourable regime of tokamak operation.

View Accepted Manuscript (DOE)

Research Organization:: University of Maryland, College Park, MD (United States)

Sponsoring Organization:: USDOE Office of Science (SC), Fusion Energy Sciences (FES)

Grant/Contract Number:: FG02-93ER54197

OSTI ID:: 1991761

Journal Information:: Journal of Plasma Physics, Journal Name: Journal of Plasma Physics Journal Issue: 1 Vol. 89; ISSN 0022-3778

Publisher:: Cambridge University PressCopyright Statement

Country of Publication:: United States

Language:: English

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