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Development of the DESC Equilibrium and Optimization Suite and Its Application to Omnigenous Stellarators.

Record Type:	Language materials, manuscript : Monograph/item
Title/Author:	Development of the DESC Equilibrium and Optimization Suite and Its Application to Omnigenous Stellarators./
Author:	Dudt, Daniel William.
Description:	1 online resource (147 pages)
Notes:	Source: Dissertations Abstracts International, Volume: 85-12, Section: B.
Contained By:	Dissertations Abstracts International85-12B.
Subject:	Mechanical engineering. -
Online resource:	click for full text (PQDT)
ISBN:	9798382810775

Development of the DESC Equilibrium and Optimization Suite and Its Application to Omnigenous Stellarators.
Dudt, Daniel William.

Development of the DESC Equilibrium and Optimization Suite and Its Application to Omnigenous Stellarators. - 1 online resource (147 pages)

Source: Dissertations Abstracts International, Volume: 85-12, Section: B.

Thesis (Ph.D.)--Princeton University, 2024.

Includes bibliographical references

This dissertation presents the research that has resulted in the development of DESC, a new stellarator equilibrium and optimization suite. DESC is fundamentally a pseudo-spectral optimization package that has been applied to solving partial differential equations of interest to stellarators. This thesis studies the problems of solving for three-dimensional ideal magnetohydrodynamic (MHD) equilibria and optimizing those equilibria for good particle confinement through quasi-symmetry and omnigenity. By taking advantage of advanced numerical methods, the code can solve equilibria more accurately and explore the full parameter space of stellarators much faster than conventional tools.DESC directly solves the fixed-boundary ideal MHD equilibrium force balance equations in real space. Discretizing with global Fourier-Zernike basis functions properly treats the magnetic axis and minimizes the number of coefficients needed to describe the nested flux surfaces. Equilibria are computed and compared against the benchmark code VMEC for both axisymmetric and non-axisymmetric examples, and the results show fast convergence rates and solutions with low errors throughout the plasma volume.Optimizing these equilibria for various objectives requires only a single equilibrium solution at each optimization step thanks to automatic differentiation. With just-in-time compilation and GPU compatibility, high-dimensional stellarator optimizations run in orders of magnitude less computation time with DESC relative to other approaches. The theory of this optimization algorithm is presented along with examples of quasi-symmetry optimizations, and the results are compared to the conventional code STELLOPT. Three different forms of quasi-symmetry objectives are showcased, and their relative advantages are discussed.Quasi-symmetry is not the only way to ensure good neoclassical confinement in a stellarator: omnigenity is the more general property of toroidal magnetic fields that confine particles. Every equilibrium previously found to approximate omnigenity has been either axisymmetric, quasi-symmetric, or has poloidally closed contours of magnetic field strength B. However, general omnigenous equilibria are a much larger design space than these subsets. A new model is presented to represent and discover the full parameter space of omnigenous equilibria. Examples far from quasi-symmetry with poloidally, helically, and toroidally closed B contours are shown to have low neoclassical transport and fast particle losses.

Electronic reproduction.
Ann Arbor, Mich. :
ProQuest,
2024

Mode of access: World Wide Web

ISBN: 9798382810775Subjects--Topical Terms:

557493
Mechanical engineering.
Subjects--Index Terms:

Stellarator equilibriumIndex Terms--Genre/Form:

554714
Electronic books.

Development of the DESC Equilibrium and Optimization Suite and Its Application to Omnigenous Stellarators.
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520 $a This dissertation presents the research that has resulted in the development of DESC, a new stellarator equilibrium and optimization suite. DESC is fundamentally a pseudo-spectral optimization package that has been applied to solving partial differential equations of interest to stellarators. This thesis studies the problems of solving for three-dimensional ideal magnetohydrodynamic (MHD) equilibria and optimizing those equilibria for good particle confinement through quasi-symmetry and omnigenity. By taking advantage of advanced numerical methods, the code can solve equilibria more accurately and explore the full parameter space of stellarators much faster than conventional tools.DESC directly solves the fixed-boundary ideal MHD equilibrium force balance equations in real space. Discretizing with global Fourier-Zernike basis functions properly treats the magnetic axis and minimizes the number of coefficients needed to describe the nested flux surfaces. Equilibria are computed and compared against the benchmark code VMEC for both axisymmetric and non-axisymmetric examples, and the results show fast convergence rates and solutions with low errors throughout the plasma volume.Optimizing these equilibria for various objectives requires only a single equilibrium solution at each optimization step thanks to automatic differentiation. With just-in-time compilation and GPU compatibility, high-dimensional stellarator optimizations run in orders of magnitude less computation time with DESC relative to other approaches. The theory of this optimization algorithm is presented along with examples of quasi-symmetry optimizations, and the results are compared to the conventional code STELLOPT. Three different forms of quasi-symmetry objectives are showcased, and their relative advantages are discussed.Quasi-symmetry is not the only way to ensure good neoclassical confinement in a stellarator: omnigenity is the more general property of toroidal magnetic fields that confine particles. Every equilibrium previously found to approximate omnigenity has been either axisymmetric, quasi-symmetric, or has poloidally closed contours of magnetic field strength B. However, general omnigenous equilibria are a much larger design space than these subsets. A new model is presented to represent and discover the full parameter space of omnigenous equilibria. Examples far from quasi-symmetry with poloidally, helically, and toroidally closed B contours are shown to have low neoclassical transport and fast particle losses.
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