Linear ion-scale microstability analysis of high and low-collisionality NSTX discharges and NSTX-U projections

Clauser, C. F.; Guttenfelder, W.; Rafiq, T.; Schuster, E.

doi:10.1063/5.0102169

Linear ion-scale microstability analysis of high and low-collisionality NSTX discharges and NSTX-U projections

Journal Article · Sat Oct 01 00:00:00 EDT 2022 · Physics of Plasmas

DOI:https://doi.org/10.1063/5.0102169· OSTI ID:1896709

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Lehigh University, Bethlehem, Pennsylvania 18015, USA; Lehigh university
Princeton Plasma Physics Laboratory, Princeton, New Jersey 08540, USA
Lehigh University, Bethlehem, Pennsylvania 18015, USA

Linear gyrokinetic simulations were conducted to investigate ion-gyroradius-scale micro-instability predictions for high-beta NSTX discharges and NSTX-U projections that span over an order of magnitude variation in collisionality. A complex mix of microtearing modes and hybrid trapped electron modes/kinetic ballooning modes (TEM/KBM) is predicted for all experimental or projected conditions. Ion temperature gradient (ITG) instabilities are typically stable in the NSTX discharges investigated, consistent with the observed neoclassical ion thermal transport. ITG thresholds inferred from the simulations are typically much higher than the experimental NSTX gradients, as well as the projected gradients in the NSTX-U scenario, which assumed ion temperatures limited by neoclassical transport only. The analysis suggests ITG instabilities are unlikely to contribute significant anomalous thermal losses in high-beta, lower collisionality NSTX-U scenarios. On the other hand, the NSTX experimental profiles and NSTX-U projections are predicted to be very close to the predicted onset of unstable KBM at most radii investigated. The proximity of the various discharges to the KBM instability threshold implies it may play an important role in setting profile shapes and limiting global energy confinement. Here, it remains to be understood and predicted how KBM contributes to multi-channel transport (thermal and particle transport, for both ions and electrons) in a way that is consistent with experimental inferences.

View Accepted Manuscript (DOE)

Research Organization:: Lehigh Univ., Bethlehem, PA (United States)

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

Grant/Contract Number:: SC0021385; SC0013977

OSTI ID:: 1896709

Alternate ID(s):: OSTI ID: 1895496
OSTI ID: 1896712

Journal Information:: Physics of Plasmas, Journal Name: Physics of Plasmas Journal Issue: 10 Vol. 29; ISSN 1070-664X

Publisher:: American Institute of Physics (AIP)Copyright Statement

Country of Publication:: United States

Language:: English

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Linear ion-scale micro-stability analysis of high and low-collisionality NSTX discharges and NSTX-U projections Clauser, Cesar; Guttenfelder, Walter; Rafiq, Tariq Princeton Plasma Physics Laboratory (PPPL), Princeton, NJ (United States) https://doi.org/10.11578/1888254	dataset	January 2022

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