Abstract
We propose to optimize the nonlinear beam dynamics of existing and future storage rings with direct online optimization techniques. This approach may have crucial importance for the implementation of diffraction limited storage rings. In this paper considerations and algorithms for the online optimization approach are discussed. We have applied this approach to experimentally improve the dynamic aperture of the SPEAR3 storage ring with the robust conjugate direction search method and the particle swarm optimization method. The dynamic aperture was improved by more than 5 mm within a short period of time. Experimental setup and results are presented.
Highlights
In a storage ring accelerator, sextupole magnets are used to cancel the energy dependence of the focusing force of quadrupole magnets
Reducing the impact of the nonlinear forces of the sextupoles in order to gain large dynamic aperture and momentum aperture is crucial for the lattice design of a storage ring, and it has become more challenging in recent years as new rings push for lower emittances, which typically require stronger focusing and more lattice periods and in turn more and stronger sextupole magnets
In the following we will discuss the online nonlinear dynamics optimization for the SPEAR3 storage ring with the robust conjugate direction search (RCDS) and particle swarm optimization (PSO) methods, which may serve as an illustration of the above considerations
Summary
In a storage ring accelerator, sextupole magnets are used to cancel the energy dependence of the focusing force of quadrupole magnets (i.e., chromaticity correction). In the case of a large ring with many sextupole magnets, the incomplete cancellation could add up to give large errors to the resonance driving terms (RDTs), which may cause the nonlinear beam dynamics of the real ring to deviate significantly from the design model. Another source of errors is the differences of the nonlinear elements in the design model and the real ring. In the following we discuss considerations of the online nonlinear dynamics optimization approach and present experimental results of the application of this approach to the SPEAR3 storage ring
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