CEPC对撞区最终聚焦系统的设计研究

The discovery of the Higgs-like boson at the LHC has placed the focus on the need to study the properties of this new particle with high precision. Many labs around the world have showed their interests on building electron positron colliders as Higgs factories to investigate the features of the Higgs boson. A long term plan was proposed by IHEP that a circular e+-e- collider (CEPC) will be built as the Higgs factory in China and then can be converted to a super p-p collider (SppC) as a discovery machine for new particles and physics in the far future. The R & D of CEPC project is very difficult, especially for the IR section. In order to give a good design of Final Focus System (FFS) which fulfills the dynamic aperture requirement of CEPC and also prepare the CDR writing for the next step, we hope to make deeper design study of CEPC FFS optics and meanwhile to publish some high level research papers with the support of NSFC. In addition, this study is not only helpful to the CEPC project but also meaningful to the next international scientific machine aimed for future high energy physics study. Some new issues in accelerator physics will come out along with the whole design of Final Focus System (FFS), which would contribute to training of high quality professionals and development of certain field in high energy physics.

在欧洲核子中心LHC上的重大实验结果Higgs 粒子一经发现，立刻受到全球高能物理学界的广泛关注。全球高能物理协会正在积极推动下一代高能轻子对撞机希格斯工厂的预研工作，中国方面也在积极筹备对希格斯工厂的设计研究，高能物理研究所提出了一机两用的长远设想，即建造下一代环形正负电子对撞机（CEPC）并适时转为质子对撞机（SppC）。CEPC的预研工作面临诸多难题，对撞区的设计尤为突出。我们希望借助本基金的支持，开展对撞区部分的物理设计研究，最终完成满足CEPC动力学孔径要求的对撞区光学系统的设计，为CDR的撰写做好准备，同时发表一些高水平的研究论文。本课题的意义不局限于CEPC这一台机器，对于未来国际高能物理装置的发展具有普适性。在整个对撞区的设计过程中，必然会挖掘出一些新的加速器物理问题，有助于培养高水平的专门人才，促进学科发展。

希格斯粒子是粒子物理“标准模型”预言的解释物质质量起源的粒子。2012年Higgs粒子在LHC上被发现后，全球高能物理学界开始积极推动下一代超大型高能对撞机的建造，欧洲核子中心CERN提出了FCC项目，我国科学家提出了CEPC-SPPC项目，装置周长都大幅度增加，对撞亮度也提高近两个量级，所以要求对撞点处的束流截面极小，对撞区的设计没有现成的经验参照，所以开展对撞区的设计研究很有必要，很具创新性和挑战性。. 本项目的研究探索出一套基于先进crab waist理念及局域色品校正的对撞区lattice设计方法，同时结合环形加速器动力学孔径优化方法，给出了能够满足CEPC亮度需求的对撞区设计，参与了CEPC加速器两部技术报告的撰写，完成了CEPC加速器CDR报告的正式发表和国际评审。同时，从本项目中积累起的极小对撞点对撞区设计及动力学孔径优化方法及经验，可以应用于未来任何一台小对撞点的对撞机，其中也包括直线对撞机。. 整个课题按计划稳步实施，进展顺利，达到预期目标。课题研究过程中发表SCI期刊文章及国际知名会议文章不下8篇，培养出3位该领域优秀青年骨干人才及1位优秀博士毕业生。