紧凑型回旋加速器作为重离子医学专用装置同步加速器的注入器，其引出系统设计所用的磁场为TOSCA模型计算磁场。通过单粒子轨道计算确定引出系统的元件类型及基本参数；通过多粒子跟踪确定最终的元件参数和束流参数。为了提高引出效率，改善引出束流品质，在引出位置磁场梯度较大的位置，安放了一块C型磁铁，以改善此处的磁场梯度。同时，为了消除此C型磁铁对主磁场的影响，在此区域安放了一对线圈。计算结果表明引出系统的设计能够保证引出束流的强度和品质符合同步加速器的要求。

A compact cyclotron as the injector of a synchrotron which forms the heavy ion medical machine is being designed and constructed at Institute of Modern Physics, China. The required high intensity and high beam quality of the extraction beam make it difficult to design the extraction system. The magnetic field used in the design is calculated from TOSCA model. The single particle orbit is calculated to determine component types and basic parameters of the extraction system. The multi-particle tracking is done to determine the final component parameters and beam parameters. In order to improve the efficiency and beam quality of the extraction system, a C-type magnet is placed at the location, where the magnetic field gradient is very large. A pair of coil is used to eliminate the effect of the C-type magnet on the main magnetic field. Detailed calculations show the extraction beam intensity and beam quality can meet the requirement of the synchrotron.