Introduction

It is vital for a successful user operation to reproduce and stabilize a previously established reference orbit (``Golden Orbit'') within 1/10th of the vertical beam size corresponding to $\approx$ 1 $\mu$m at the location of the insertion devices (IDs). As a consequence, the digital BPM [1] and corrector hardware [2] have been designed in order to allow for the implementation of a Fast Orbit Feedback (FOFB) that is able to suppress residual orbit oscillations up to $\approx$ 100 Hz with attenuation factors of $>$ 10. The FOFB imposes tight constraints on the capabilities and reliability of the involved subsystems since the feedback loop runs at a sampling rate of 4 kHz on the DSP level of the BPM hardware.
In order to gain experience with the various subsystems, a Slow Orbit Feedback (SOFB) with much relaxed requirements ($<$ 3 Hz correction rate) has been implemented, communicating with the underlying hardware components through a ``CDEV Server'' which is connected to the EPICS based control system [3].