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DOE OSTI · 3371694

Spectrally accurate, reverse-mode differentiable bounce-averaging algorithm and its applications

Unalmis, Kaya [Princeton Univ., NJ (United States)] (ORCID:0000000217556764)·Gaur, Rahul [Princeton Univ., NJ (United States)] (ORCID:0000000343679052)·Conlin, Rory [Univ. of Maryland, College Park, MD (United States)] (ORCID:0000000183662111)·Panici, Dario [Princeton Univ., NJ (United States)] (ORCID:0000000307364360)·Kolemen, Egemen [Princeton Univ., NJ (United States); Princeton Plasma Physics Laboratory (PPPL), Princeton, NJ (United States)] (ORCID:0000000342123247)
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Abstract

We present a fast, spectrally (exponentially) accurate, automatically differentiable bounce-averaging algorithm that is used to simplify kinetic models. Using this algorithm, implemented in the DESC stellarator optimisation suite, we can perform efficient optimisation of many objectives to improve stellarator performance, such as the effective ripple đťś– eff metric for the neoclassical transport coefficient in the low collisionality regime and proxies for energetic particle confinement. For the first time, we optimise a finite-beta stellarator to directly reduce neoclassical ripple transport using reverse-mode differentiation. This ensures the computational cost of differentiation is independent of the number of controllable parameters.

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Unalmis, Kaya [Princeton Univ., NJ (United States)] (ORCID:0000000217556764), Gaur, Rahul [Princeton Univ., NJ (United States)] (ORCID:0000000343679052), Conlin, Rory [Univ. of Maryland, College Park, MD (United States)] (ORCID:0000000183662111), Panici, Dario [Princeton Univ., NJ (United States)] (ORCID:0000000307364360), Kolemen, Egemen [Princeton Univ., NJ (United States); Princeton Plasma Physics Laboratory (PPPL), Princeton, NJ (United States)] (ORCID:0000000342123247). 2026-06-10. Spectrally accurate, reverse-mode differentiable bounce-averaging algorithm and its applications. https://doi.org/10.1017/s0022377826101652

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