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

Clauser, Cesar ; Guttenfelder, Walter ; Rafiq, Tariq ; Schuster, Eugenio
Issue date: 2022
Rights:
Creative Commons Attribution 4.0 International (CC BY)
Cite as:
Clauser, Cesar, Guttenfelder, Walter, Rafiq, Tariq, & Schuster, Eugenio. Linear ion-scale micro-stability analysis of high and low-collisionality NSTX discharges and NSTX-U projections [Data set]. Princeton Plasma Physics Laboratory, Princeton University. https://doi.org/10.11578/1888254
@electronic{clauser_cesar_unknown,
  author      = {Clauser, Cesar and
                Guttenfelder, Walter and
                Rafiq, Tariq and
                Schuster, Eugenio},
  title       = {{Linear ion-scale micro-stability analysi
                s of high and low-collisionality NSTX di
                scharges and NSTX-U projections}},
  publisher   = {{Princeton Plasma Physics Laboratory, Pri
                nceton University}},
  url         = {https://doi.org/10.11578/1888254}
}
Description:

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. 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.

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1 README.txt 266 Bytes
2 fig10.txt 1.78 KB
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52 fig9_abc.txt 26.6 KB
53 fig9_def.txt 26.3 KB
54 fig9_ghi.txt 26.4 KB