Exploration of the parameter space of quasisymmetric stellarator vacuum fields through adjoint optimisation

Nies, Richard; Paul, Elizabeth J.; Panici, Dario; Hudson, Stuart R.; Bhattacharjee, Amitava

doi:10.1017/s002237782400093x

Exploration of the parameter space of quasisymmetric stellarator vacuum fields through adjoint optimisation

Journal Article · Thu Dec 19 23:00:00 EST 2024 · Journal of Plasma Physics

DOI:https://doi.org/10.1017/s002237782400093x· OSTI ID:2496685

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Princeton Univ., NJ (United States); Princeton Plasma Physics Laboratory (PPPL), Princeton, NJ (United States)
Columbia Univ., New York, NY (United States)
Princeton Univ., NJ (United States)
Princeton Plasma Physics Laboratory (PPPL), Princeton, NJ (United States)

Optimising stellarators for quasisymmetry leads to strongly reduced collisional transport and energetic particle losses compared with unoptimised configurations. Although stellarators with precise quasisymmetry have been obtained in the past, it remains unclear how broad the parameter space is where good quasisymmetry may be achieved. We study the range of aspect ratios and rotational transform values for which stellarators with excellent quasisymmetry on the boundary can be obtained. A large number of Fourier harmonics is included in the boundary representation, which is made computationally tractable by the use of adjoint methods to enable fast gradient-based optimisation and by the direct optimisation of vacuum magnetic fields, which converge more robustly compared with solutions from magnetohydrostatics. Several novel configurations are presented, including stellarators with record levels of quasisymmetry on a surface, three field period quasiaxisymmetric stellarators with substantial magnetic shear, and compact quasisymmetric stellarators at low aspect ratios similar to tokamaks.

View Accepted Manuscript (DOE)

Research Organization:: Princeton Plasma Physics Laboratory (PPPL), Princeton, NJ (United States)

Sponsoring Organization:: USDOE; Simons Foundation

Grant/Contract Number:: SC0022005; SC0024548; SC0016072; AC02-76CH03073; AC02-09CH11466

OSTI ID:: 2496685

Journal Information:: Journal of Plasma Physics, Journal Name: Journal of Plasma Physics Journal Issue: 6 Vol. 90; ISSN 0022-3778

Publisher:: Cambridge University PressCopyright Statement

Country of Publication:: United States

Language:: English

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