Linear And Nonlinear Optical Parameter Optimization For Electron Storage Ring Using Genetic Algorithm

Brightness, which is determined by the radiation device and beam parameters, is the key performance parameter for synchrotron light source. An important job for the storage ring designers is to increase the light brightness by minimizing the beam emittance. To achieve higher brightness and better transverse coherence, the beam emittance of next generation synchrotron radiation light source would be in the order of10pm.rad, which is lower than that of third generation light source by2-3orders. Except for minimizing beam emittance, there is a challenging task in lattice design process, which is enlarging dynamic aperture limited by stronger nonlinear effects in diffraction-limited storage ring. The main purpose of this thesis is to develop new method to optimize linear and nonlinear parameters of storage ring.In this thesis, we introduced the parallelized genetic algorithm to storage ring lat-tice parameters optimization, where dynamic aperture tracking results were used as optimization goal directly. Generally, the dynamic aperture cannot be expressed by some analytical formula, so that we made a numerical standard by multi-particle track-ing. The code developed by this thesis will automatically find best solutions with good dynamic aperture properties using genetic algorithm, which has excellent global opti-mum capability. For different problems, the GLASS method, single objective genetic algorithm and multi-objective genetic algorithm (NSGA-Ⅱ) were applied to systemati-cally analyze the storage ring parameters optimization issues. First of all, the GLASS method was used in linear lattice design of low emittance mode for the Hefei light source. The lattice has few magnets to be varied, so that it is very easy to get a satis-factory lattice by scanning from coarse-grained to fine-grained. For the Hefei upgrade project we used multi-objective genetic algorithm to design achromatic mode, non-achromatic mode, low momentum compaction factor mode, and high-low beta hybrid mode. Hefei advanced light source is proposed storage ring based light source with ullralow beam emittance. where it is difficult to apply above methods due to many vari-ables. So that, we used the genetic algorithm to search for the feasible regions firstly and then let the linear variables vary in the obtained regions to simultaneously optimize the linear and nonlinear parameters. The developed code provides a feasible solution set with low emittance and large dynamic aperture and the designer can find desired design parameter from the solution set according different consideration. In a word, an optimization software for storage ring lattice design was developed in this thesis. This code has distinct features, including the ability to simultaneously optimize the linear and nonlinear beam parameters, direct usage of dynamic aperture tracking result as optimization goal to avoid the incomplete relation between DA and known nonlinear indicators. The parallelized multi-objective genetic algorithm will make the lattice design process more direct and efficient.