Abstract
A multi-objective genetic algorithm is developed for optimizing nonlinearities in diffraction limited storage rings. This algorithm determines sextupole and octupole strengths for chromaticity correction that deliver optimized dynamic aperture and beam lifetime. The algorithm makes use of dominance constraints to breed desirable properties into the early generations. The momentum aperture is optimized indirectly by constraining the chromatic tune footprint and optimizing the off-energy dynamic aperture. The result is an effective and computationally efficient technique for correcting chromaticity in a storage ring while maintaining optimal dynamic aperture and beam lifetime. This framework was developed for the Swiss Light Source (SLS) upgrade project.
Highlights
Multiobjective genetic algorithms have found much success providing nonintuitive solutions to problems that are not adequately solved by analytic methods
The beam lifetime would be maximized by maximizing the momentum aperture, which is the largest momentum kick that an initially on-axis particle can receive without being lost downstream
One feature of this algorithm is the use of dominance constraints to encourage individuals in the early population to take on properties that will later on contribute to healthy objective values
Summary
Multiobjective genetic algorithms have found much success providing nonintuitive solutions to problems that are not adequately solved by analytic methods. A genetic algorithm is developed for optimizing dynamic aperture and beam lifetime using sextupole and octupole strengths in next-generation diffraction limited storage rings (DLSR). The established technique for optimizing nonlinearities in a storage ring is resonant driving term minimization and was developed for the original Swiss Light Source (SLS) [6]. It is a Lie algebra expansion of the transfer map in driving terms that are functions of the sextupole strength. These terms drive higher order chromatic tune shifts, amplitude dependent tune shifts, and resonances.
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