A novel objective function minimizes resonant trapped energetic particle losses in stellarators
Abstract
Near-omnigenous stellarators are susceptible to energetic particle (EP) losses due to resonances between trapped EPs and non-omnigenous perturbations to the magnetic field. Existing bounce-averaged objectives such as Γc, Γδ , and Γα target the non-resonant misalignment of drift and flux surfaces, but they do not capture resonant convective or diffusive motion. We develop a discrete map theory for the bounce points of trapped EPs in near-omnigenous fields, in which phase-space islands form due to resonance between the precession and bounce frequencies. We introduce Δres, a differentiable, bounce-averaged objective function that penalizes the widths of these islands, promoting phase-space integrability. Optimizing a quasi-axisymmetric configuration using Δres combined with a two-term quasi-symmetry objective yields a factor-of-four improvement in EP confinement by displacing low-order resonances and forming EP transport barriers. Δres is a powerful tool to combat both resonant convective and diffusive losses in power plant-relevant stellarators.
Related
- Frequency-inference method for reduced modeling of energetic particle modes (EPM) utilizing resonant auto-optimization remnants of imperfect time-scale separation
- Runaway electrons in stellarators: Unlikely or unavoidable?
- On the Shafranov shift in stellarators
- Gradient-Based Construction of Collisionless Steady-State Guiding-Center Distributions in Tokamaks and Stellarators
- The shear Alfvén continuum of optimized stellarators
BibTeX
@misc{labbate2026novel,
title = {{A novel objective function minimizes resonant trapped energetic particle losses in stellarators}},
author = {John Anthony Labbate and Elizabeth J. Paul and Amelia Chambliss},
howpublished = {arXiv},
year = {2026},
month = sep,
doi = {10.48550/arxiv.2609.01890},
eprint = {2609.01890},
archivePrefix = {arXiv},
url = {https://arxiv.org/abs/2609.01890},
note = {CC BY 4.0},
}
RIS
TY - UNPB
TI - A novel objective function minimizes resonant trapped energetic particle losses in stellarators
AU - John Anthony Labbate
AU - Elizabeth J. Paul
AU - Amelia Chambliss
PY - 2026
DA - 2026/09/01
PB - arXiv
DO - 10.48550/arxiv.2609.01890
UR - https://arxiv.org/abs/2609.01890
AB - Near-omnigenous stellarators are susceptible to energetic particle (EP) losses due to resonances between trapped EPs and non-omnigenous perturbations to the magnetic field. Existing bounce-averaged objectives such as Γ_c, Γ_δ , and Γ_α target the non-resonant misalignment of drift and flux surfaces, but they do not capture resonant convective or diffusive motion. We develop a discrete map theory for the bounce points of trapped EPs in near-omnigenous fields, in which phase-space islands form due to resonance between the precession and bounce frequencies. We introduce Δ_res, a differentiable, bounce-averaged objective function that penalizes the widths of these islands, promoting phase-space integrability. Optimizing a quasi-axisymmetric configuration using Δ_res combined with a two-term quasi-symmetry objective yields a factor-of-four improvement in EP confinement by displacing low-order resonances and forming EP transport barriers. Δ_res is a powerful tool to combat both resonant convective and diffusive losses in power plant-relevant stellarators.
ER -