环形加速器自旋动力学研究新方法探索

极化束是高能物理实验用于研究标准模型和标准模型以外新物理的重要工具。精确了解环形加速器自旋动力学，并寻找有效方法减小自旋tune分散和避开自旋共振，是获得极化束的关键步骤。针对目前lattice设计上缺少通用可行的极化优化方案，以及亮度和极化度很难兼顾等问题，该项目将构建能够把非线性轨道和自旋动力学信息同时包含在内的新物理模型，自旋动力学孔径。基于该模型，研究环形加速器中的各类自旋共振问题，并结合粒子群优化算法研究通过调节六极铁参数减小自旋tune分散、实现非线性轨道和自旋动力学同时优化的方法，从而保证同时得到好的亮度和极化度。另外，该项目还将研究紧凑的螺线管型西伯利亚蛇的快速设计方法，并用自旋动力学孔径模型加以验证。

Polarized beam is an important tool for studying standard model and the new physics beyond standard model in high energy physics experiment. Accurate understanding of spin dynamics in circular accelerator and finding effective ways to reduce spin tune spread and avoid spin resonances are the critical steps to obtain polarized beam. In view of the lack of a general and feasible polarization optimization scheme in lattice design, as well as the difficulty in balancing luminosity and polarization, this project will construct a new physical model that can incorporate both nonlinear orbit and spin dynamics information, called spin dynamic aperture. Based on this model, various spin resonance problems in circular accelerator are studied. Combining with particle swarm optimization algorithm, the method of simultaneously optimizing nonlinear orbit and spin dynamics by adjusting sextupole parameters to reduce spin tune spread is studied, so as to ensure good luminosity and polarization at the same time. In addition, the project will study a rapid design method for a compact solenoid Siberian Snake, which will be validated by the spin dynamic aperture model too.