合肥光源储存环上八极磁铁的动力学效应分析

 为达到合肥光源二期工程通用模式的设计流强，在储存环上选择垂直方向β函数比较大的位置增加一组八极磁铁。该组八极磁铁对水平方向动力学孔径影响很小，虽然垂直方向动力学孔径明显减小，但仍然大于物理孔径，不会影响束流的注入积累过程。该组八极磁铁产生的垂直方向振荡频率分散可以提供ms量级的Landau阻尼时间，将明显增强抑制垂直方向束流集体不稳定性的能力。该组八极磁铁投入运行后，合肥光源注入积累过程明显改善，注入流强从无八极磁铁时的约100 mA提高到330 mA左右。

Dynamic effects of octupole-magnets in HLS storage ring

In order to attain the design beam intensity of Phase II Project of Hefei Light Source(HLS),one family of octupoles were installed in the place where vertical Batatron function is relatively large in HLS storage ring.After adding octupoles,the horizontal dynamic aperture is little affected but the vertical dynamic aperture decreased drastically.This is not detrimental to beam injection and accumulation,because the vertical dynamic aperture is still larger than physical aperture.The vertical oscillation frequency spread generated by octupoles can provide Landau damping time about several microseconds,which is very helpful to overcome vertical collective instabilities in HLS storage ring,where radiation damping time is 1.4 s.One year's operation has demonstrated the effectiveness of octupoles.The injected beam intensity,which was about 100 mA without octupoles,was improved to more than 330 mA by octupoles.