Performance of a Fast Closed Orbit Feedback System with Combined Fast and Slow Correctors

摘要

For NSLSII closed orbit feedback system, in order to limit the noise caused by digital step changes of the power supplies in the feedback system, the angular kick corresponding to the last bit of the power supplies for the fast correctors must be smaller than 3 nrad. On the other hand, to carry out closed orbit alignment or orbit correction after a long term drift, they need strong correctors with 0.8 mrad kick strength. In order to avoid the requirement of correctors with both large strength and very small minimum step size, they consider separate sets of slow correctors with large strength and fast correctors with smaller maximum strength. In order to avoid fast and slow feedback systems working in parallel, and avoid the possible interaction between two feedback systems, they consider the possibility of using only one fast feedback system with slow correctors periodically removing the DC components of the fast correctors so that the DC components in fast feedback system do not accumulate to reach saturation even after a large long term drift of the closed orbit motion. They report on simulation of the performance of such a combined system for NSLSII in this paper.