DEPU对上海光源储存环的影响与补偿

Compensations of double elliptical polarization undulator effects on the SSRF storage ring

上海光源储存环安装了一套由两台椭圆极化波荡器组成的插入件(DEPU),该插入件尤其是其中一台椭圆极化波荡器的积分场误差引起了闭轨畸变、工作点漂移、耦合度变化、动力学孔径减小等多种效应,这些效应对上海光源储存环的正常运行造成了极大影响。采用校正线圈前馈将最大闭轨畸变降低到10μm的水平,采用四极铁强度前馈将工作点漂移控制在0.001左右,采用斜四极铁前馈将耦合度很好地控制在0.1%左右。通过六极铁在线优化解决了动力学孔径退化的问题,将注入效率保持在80%以上。在接近4年的运行中,补偿方案工作表现很好,轨道补偿的前馈还在不断地完善中。

A pair of Apple-II type EPU （double elliptical polarization undulators, DEPU） was installed in the SSRF storage ring. The unwanted integral magnetic field errors induced by the devices lead to closed-orbit distortions （COD）, tune shifts, coupling variation, reduction of the dynamic aperture and so on. These effects deteriorate the operation performance of the SSRF. Feedforward tables of corrector coils, quadrupoles and skew quadrupoles are used to correct the COD, tune shifts and coupling, respectively. The max COD keeps smaller than 10 μm, the tune shifts keep around 0. 001 and the coupling keeps 0.1%. Sextupole strengths were optimized to restore the dynamic aperture, the injection efficiency resumes to more than 80%. In the nearly 4 years operation, the compensations have been working well, and there are still more and more supplements and revisions of the feedforward tables in development for the COD corrections.