On Shear Alfvén Wave-Induced Fast Ion Losses in Optimized Stellarator Equilibria
ORAL
Abstract
Recent advances in stellarator optimization [1, 2] have achieved fusion power-plant (FPP) relevant levels of energetic particle (EP) confinement [3] from equilibrium magnetic fields. However, MHD waves can cause prompt EP losses [4]. An important transport [5] mechanism is the resonant interaction of shear Alfvén waves (SAW) with energetic ions [6,7].
This work presents an assessment of SAW-induced prompt drift-orbit EP losses in optimized stellarator equilibria scaled to FPP parameters [3]. We use a hybrid MHD-kinetic vorticity model [8] with a reduced MHD model for the thermal plasma and a kinetic closure for EPs to capture EP-SAW interactions. We identify radially global SAWs in Alfvén continuum gaps [9,10] that become unstable through interactions with fusion-born alpha particles. The amplitudes at which these global SAWs cause prompt EP losses are then determined with Monte Carlo drift orbit tracing. Analysis of lost EP trajectory types [11] reveals that most losses occur for particles that transition between passing and trapped categories. Future work will extend the analysis with quasilinear models [12] to establish SAW saturation amplitudes.
1. Landreman, Paul, PRL 2022
2. Goodman et al., PRX Energy 2024
3. Bader et al., NF 2021
4. Salewski, NF 2025
5. Mynick, PoP 1993
6. White, Duarte, PoP 2023
7. Paul et al., JPP 2023
8. J. Varela et al., Frontiers 2024
9. Spong et al., PoP 2010
10. Paul et al., JPP 2025
11. Paul et al., NF 2022
12. Saby et al., NF 2025
This work presents an assessment of SAW-induced prompt drift-orbit EP losses in optimized stellarator equilibria scaled to FPP parameters [3]. We use a hybrid MHD-kinetic vorticity model [8] with a reduced MHD model for the thermal plasma and a kinetic closure for EPs to capture EP-SAW interactions. We identify radially global SAWs in Alfvén continuum gaps [9,10] that become unstable through interactions with fusion-born alpha particles. The amplitudes at which these global SAWs cause prompt EP losses are then determined with Monte Carlo drift orbit tracing. Analysis of lost EP trajectory types [11] reveals that most losses occur for particles that transition between passing and trapped categories. Future work will extend the analysis with quasilinear models [12] to establish SAW saturation amplitudes.
1. Landreman, Paul, PRL 2022
2. Goodman et al., PRX Energy 2024
3. Bader et al., NF 2021
4. Salewski, NF 2025
5. Mynick, PoP 1993
6. White, Duarte, PoP 2023
7. Paul et al., JPP 2023
8. J. Varela et al., Frontiers 2024
9. Spong et al., PoP 2010
10. Paul et al., JPP 2025
11. Paul et al., NF 2022
12. Saby et al., NF 2025
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Presenters
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Alexey Romanovich Knyazev
Columbia University
Authors
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Alexey Romanovich Knyazev
Columbia University
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Alexandra Lachmann
Columbia University
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Abdullah Syed Hyder
Columbia University
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Michael Czekanski
Cornell University
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Elizabeth J Paul
Columbia University
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William Fei
Columbia University