储存环的闭合轨道畸变校正研究

The study of closed orbit distortion correction in SSRF storage ring

在电子储存环中，弯转磁铁的场误差、转动误差和四极磁铁的横向位置偏差所产生的二极磁场分量，会导致循环电子的闭合轨道畸变（COD）。以SSRF电子储存环为例，探讨如何利用国际通用加速器程序MAD和RACETRACK进行第三代储存环的闭合轨道畸变校正。首先对SSRF电子储存环闭合轨道校正方案中的校正子和BPM不同安放方案作了比较研究，结果表明，采用每个单元安放10BPM（安在六极磁铁附近），每个普通单元安装8个校正子（水平、垂直方向各4个）的方案是可行的，可以将COD均方根校正到0．1mm以下。并且探讨了弯转磁铁场误差、转动误差和四极磁铁位置偏差、BPM读数误差及校正子误差对COD均方根和校正子最大强度的影响。结果表明，通过闭合轨道畸变校正后，可将SSRF电子储存环的动力学孔径恢复到理想情况下的75％以上。

In electronic storage ring, the bending magnet field error, rotational error andthe quadrupole displacement error produce dipole field, which will induce the closed orbit distortion (COD) of cycle electrons. Different corrector and BPM placementschemes were compased and studied, it is found that the scheme with 10 BPM (BPMclose to the sextupole ) and 4 horizontal and 4 vertical correctors in each cell isacceptable, and the COD Rms. could be suppressed to be under 0.1mm. The effect ofthe bending magnet field error, rotational error and the quadrupole displacementerror to the COD and how the BPM reading error and correctors error influenced thecorrection result were studied. Through COD correction the dynamic aperture couldbe resumed to be above 75% of the ideal dynamic aperture.