Storage Ring Lattice Design,optimization And Related Theoretical Research

Diffraction limited storage ring(DLSR)is the future development direction of light sources.The main difference between DLSR and the third-generation light sources is that the emittance is lower.It is close to the diffraction limit of photons.The lower the emittance,the higher the brightness of the light.There are many ways to reduce the emittance.Among them,the multi-bend achromat(MBA)method is the most popular one.It increases the number of dipole irons in a single unit,which can reduce the emittance very effectively.Use 7BA lattice has also become first choice for new light sources and light source transformations.In addition,some other methods can also reduce the emittance by changing related parameters from different angles,such as the use of antibend,longitudinal gradient dipole bend method,Robinson Wiggler,and transverse gradient dipole bend method.In order to cope with the increase number of users and the higher demand of them for light,we need to transform the Shanghai Light Source to improve the performance and reduce the emittance on the base of existing storage ring.At present,the circumference of the Shanghai Light Source is 432 m,and the emittance is3.6nm·rad.In the reconstruction process,we will keep the circumference and the length of the straight section as constant as possible.This article first introduces the main methods of reducing the emittance,and then elaborates the design process of the magnetic focusing structure used in the transformation of Shanghai Light Source.The 7BA structure is mainly used,and on the base of 7BA,anti-bend and longitudinal gradient dipole bend are added.Iron,this method greatly reduces the emittance,which can be as low as 100pm·rad.During the design process,the minimum emittance that can be achieved at each stage was explored,and various aspects such as magnet technology and funding were considered to ensure the basic requirements for actual operation.Because the low emittance also brings about the problem of too small dynamic aperture,in order to make the dynamic aperture large enough to ensure beam injection,after completing the main design,simple dynamic aperture optimization was carried out.In addition to the 7BA-based magnetic focusing structure design,single-turn?bump and single-turn dispersion bump injection methods are also designed to ensure efficient beam injection for the diffraction limit loop.The longitudinal beam injection has been non-linearly optimized,and the high frequency frequency suitable for the injection of the diffraction limit loop of the Shanghai Light Source has been found.A storage ring for EUV lithography is designed,and the nonlinear optimization is carried out.It is analyzed that the working point should avoid the resonance line as much as possible,and the third harmonic cavity is used to stretch the bunch to extend the beam life.The light source has low complexity and cost.As an alternative,it provides us with a new choice for a variety of applications in EUV lithography,and has important value,providing design reference for similar facilities in the future.