作为CSNS/RCS横向束流准直系统的关键部件，次级准直器用于吸收经主准直器散射后不在预定轨道的束晕粒子，其工作原理决定了该设备要求满足强辐射环境下的稳定性、超高真空及高定位精度等要求。基于主准直器的设计及研制经验，对次级准直器结构方案及控制系统进行详细设计。针对关键部件吸收体，结合辐射防护分析结果，考虑水冷降温的方式，设计了控制程序，通过有限元分析软件ANSYS对其进行瞬态热分析，保证吸收体设计的可行性。

As the key components of rapid cycling synchrotron of China Spallation Neutron Source (CSNS/RCS) collimation system, secondary collimators are used to absorb the unconstrained halo particles which are scattered by primary collimator’s scrapers, they should meet the special requirements of high stability, ultra-high vacuum, high positioning accuracy and so on. Based on the design and manufacturing experience of primary collimator, the absorber which is the key part of secondary collimators is designed by using ANSYS and FLUKA, and cooling by water pipe is adopted. Combined with the control system, transient analysis has been done to ensure the feasibility of the design.