A theoretical model is presented that for the first time matches experimental measurements of the pedestal width-height Diallo scaling in the low-aspect-ratio high- β tokamak NSTX. Combining linear gyrokinetics with self-consistent pedestal equilibrium variation, kinetic-ballooning, rather than ideal-ballooning plasma instability, is shown to limit achievable confinement in spherical tokamak pedestals. Simulations are used to find the novel Gyrokinetic Critical Pedestal constraint, which determines the steepest pressure profile a pedestal can sustain subject to gyrokinetic instability. Gyrokinetic width-height scaling expressions for NSTX pedestals with varying density and temperature profiles are obtained. These scalings for STs depart significantly from that of conventional aspect ratio tokamaks.
Parisi, J. F., Guttenfelder, W., Nelson, A. O., Gaur, R., Kleiner, A., Lampert, M., Avdeeva, G., Berkery, J. W., Clauser, C., Curie, M., Diallo, A., Dorland, W., Kaye, S. M., McClenaghan, J., & Parra, F. I. (2024). Kinetic-ballooning-limited pedestals in spherical tokamak plasmas. Nuclear Fusion, 64(5). https://doi.org/10.1088/1741-4326/ad39fb
Parisi, J. F., Guttenfelder, W., Nelson, A. O., et al., "Kinetic-ballooning-limited pedestals in spherical tokamak plasmas," Nuclear Fusion 64, no. 5 (2024), https://doi.org/10.1088/1741-4326/ad39fb
@article{osti_2336637,
author = {Parisi, J. F. and Guttenfelder, W. and Nelson, A. O. and Gaur, R. and Kleiner, A. and Lampert, M. and Avdeeva, G. and Berkery, J. W. and Clauser, C. and Curie, M. and others},
title = {Kinetic-ballooning-limited pedestals in spherical tokamak plasmas},
annote = {Abstract A theoretical model is presented that for the first time matches experimental measurements of the pedestal width-height Diallo scaling in the low-aspect-ratio high- β tokamak NSTX. Combining linear gyrokinetics with self-consistent pedestal equilibrium variation, kinetic-ballooning, rather than ideal-ballooning plasma instability, is shown to limit achievable confinement in spherical tokamak pedestals. Simulations are used to find the novel Gyrokinetic Critical Pedestal constraint, which determines the steepest pressure profile a pedestal can sustain subject to gyrokinetic instability. Gyrokinetic width-height scaling expressions for NSTX pedestals with varying density and temperature profiles are obtained. These scalings for STs depart significantly from that of conventional aspect ratio tokamaks. },
doi = {10.1088/1741-4326/ad39fb},
url = {https://www.osti.gov/biblio/2336637},
journal = {Nuclear Fusion},
issn = {ISSN 0029-5515},
number = {5},
volume = {64},
place = {IAEA},
publisher = {IOP Publishing},
year = {2024},
month = {04}}
Field, A. R.; Chapman-Oplopoiou, B.; Connor, J. W.
Philosophical Transactions of the Royal Society A: Mathematical, Physical and Engineering Sciences, Vol. 381, Issue 2242https://doi.org/10.1098/rsta.2021.0228