Experience with the beam position monitor system of the BESSY II storage ring

The beam position monitor (BPM) system has bean developed at BESSY and operates in 3 different modes: the closed orbit, the single turn, and the diagnostics mode. Details of the BPM system are presented together with the result of some bench tests. The commissioning of the system was done primarily with beam-based techniques and is described in more detail. First measurements of fast and slow beam motions are presented. From the very beginning the BPM system was used successfully for the optimisation of the storage ring.