自2018年11月环形正负电子对撞机（CEPC）概念设计报告发布以后，CEPC的基本设计框架已经完成。为了满足CEPC- Z能区的能量精确测量和纵向极化束对撞物理实验的要求，我们需要及时开展CEPC-Z能区束流极化的研究，这也是CEPC进一步细化设计的必然j进程。本申请项目将对CEPC-Z能区加快辐射自极化过程、 CEPC Booster束流升能过程中退极化机制和处理、CEPC-Z能区纵向极化束流对撞等方面展开研究。我们将对极化束流进行全程跟踪模拟——从极化束流的产生，到极化束流在直线加速器和增强器中的加速，以及极化束流的传输，最后实现纵向极化束流的对撞。这些加速器物理问题的研究解决是在CEPC中实现5-10%横向极化度用于Z能区能量精确测量以及实现40-50%纵向极化度束流对撞的关键。

Since the release of the Conceptual Design Report for the Circular Electron and Positron Collider (CEPC) in November 2018, the basic design framework for CEPC has been completed. In order to meet the requirements of the accurate energy measurement and longitudinal polarization beam collision physics experiment at CEPC Z-pole, we need to carry out research on beam polarization at CEPC Z-pole in time, which is also the inevitable process for CEPC to further refine the design. This project will study the acceleration of the self-polarization process at CEPC Z-pole, the depolarization mechanism and processing in the CEPC Booster beam energy enhancement process, and the longitudinal polarization beam collision at CEPC Z-pole. We will perform a tracking simulation of the polarized beam—from the generation of the polarized beam to the acceleration of the polarized beam in the linear accelerator and Booster, as well as the transmission of the polarized beam, and finally the collision of the longitudinally polarized beams. The solution to these accelerator physics problems is the key to achieve 5-10% transverse polarization at CEPC Z-pole for accurate measurement of energy and to achieve 40-50% longitudinal polarization beam collision.