FAST ORBIT FEEDBACK

In general an orbit feedback detects the orbit oscillations induced by incoming ground waves using the beam position monitors around the ring. A lattice dependent well known correlation between monitors and corrector magnets is then used to fight the oscillation (see subsection ``Theoretical Concepts''). No information on amplitude, frequency and phase of the distortion is needed for the correction. If the noise source would be exactly known a feed forward would be much more appropriate and much easier to implement. There are two different approaches to implement a feedback. Firstly it could be tried to minimize orbit variations at each experiment individually involving only correctors around the insertion device. This would have the main disadvantage that non locality of the correction would lead to a crosstalk between the local feedbacks which could be extremely difficult to control. A much better alternative represents a global orbit feedback which tries to minimize the orbit variations at all experiments at the same time. Following this approach a global orbit feedback will be adopted at SLS.