The Performance of Slow Orbit Feedback for the PLS-II

In order to achieve orbit stability of a few pm, a global orbit feedback system is absolutely a necessary and has been operated at the Pohang Light Source (PLS) since 2005. The feedback uses a singular value decomposition (SVD) method and MATLAB channel access to experimental physics and industrial control system (EPICS) input output controller (IOC) of beam position monitors (BPMs) and correctors. However, selection for the BPM, the corrector and the number of singular values are shared in the x and the y planes of the present feedback. This causes a limit on the performance of the feedback system. Therefore, separation between the x and the y planes is required for a global orbit feedback system for PLS-II, which is an upgrade of PLS. In this paper, we describe the performance of a newly developed global orbit feedback system for PLS-II.