Energetic particle loss mechanisms in reactor-scale equilibria close to quasisymmetry

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dc.contributor.authorPaul, E. J.en
dc.contributor.authorBhattacharjee, A.en
dc.contributor.authorLandreman, M.en
dc.contributor.authorAlex, D.en
dc.contributor.authorVelasco, J. L.en
dc.contributor.authorNies, R.en
dc.date.accessioned2023-04-17T19:16:04Zen
dc.date.available2023-04-17T19:16:04Zen
dc.date.issued2022-12en
dc.description.abstractCollisionless physics primarily determines the transport of fusion-born alpha particles in 3D equilibria. Several transport mechanisms have been implicated in stellarator configurations, including stochastic diffusion due to class transitions, ripple trapping, and banana drift-convective orbits. Given the guiding center dynamics in a set of six quasihelical and quasiaxisymmetric equilibria, we perform a classification of trapping states and transport mechanisms. In addition to banana drift convection and ripple transport, we observe substantial non-conservation of the parallel adiabatic invariant which can cause losses through diffusive banana tip motion. Furthermore, many lost trajectories undergo transitions between trapping classes on longer time scales, either with periodic or irregular behavior. We discuss possible optimization strategies for each of the relevant transport mechanisms. We perform a comparison between fast ion losses and metrics for the prevalence of mechanisms such as banana-drift convection (Velasco et al 2021 Nucl. Fusion 61 116059), transitioning orbits, and wide orbit widths. Quasihelical configurations are found to have natural protection against ripple-trapping and diffusive banana tip motion leading to a reduction in prompt losses.en
dc.description.notesThe authors acknowledge fruitful conversations with R. White, H. Mynick, A. Boozer, R. Mackay, and F. Parra. A. Bader provided the Wistell-A, Ku5, NCSX, and ARIES-CS equilibria and assistance with benchmarking of the SIMSOPT code. EJP was supported by the Presidential Postdoctoral Research Fellowship at Princeton University. This research was also supported by the Simons Foundation/SFARI (560651, AB and ML). Some calculations were performed using computing resources at Princeton Plasma Physics Laboratory under DOE Contract DE-AC02-09CH11466.en
dc.description.sponsorshipPresidential Postdoctoral Research Fellowship at Princeton University; Simons Foundation/SFARI [DE-AC02-09CH11466]; DOE; [560651]en
dc.description.versionPublished versionen
dc.format.mimetypeapplication/pdfen
dc.identifier.doihttps://doi.org/10.1088/1741-4326/ac9b07en
dc.identifier.eissn1741-4326en
dc.identifier.issue12en
dc.identifier.other126054en
dc.identifier.urihttp://hdl.handle.net/10919/114527en
dc.identifier.volume62en
dc.language.isoenen
dc.publisherIOP Publishingen
dc.rightsCreative Commons Attribution 4.0 Internationalen
dc.rights.urihttp://creativecommons.org/licenses/by/4.0/en
dc.subjectfast ionsen
dc.subjectstellaratorsen
dc.subjectoptimizationen
dc.titleEnergetic particle loss mechanisms in reactor-scale equilibria close to quasisymmetryen
dc.title.serialNuclear Fusionen
dc.typeArticle - Refereeden
dc.type.dcmitypeTexten

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