FOFB Status

Up to now, the digital BPM/FOFB system and the corrector magnet system have been located in two different VME crates. This approach allowed an independent commissioning of two newly developed systems. Since the operation of the SOFB has already fulfilled the requirements of the experiments for the time being, low priority has been given to the implementation of the FOFB. On the other hand, operation of the SLS during the last couple of months has shown the importance of an ``intelligent'' BPM system which is capable of self diagnosing hardware faults. This is an important requirement for a reliable operation of the feedback system. Therefore emphasis has been put on sophisticated low level software in order to detect BPMs with spurious bad readings. When the feedback loop is closed the residual orbit fluctuations are typically in the order of $\mu$m. If both rms values of $x$ and $y$ taken over the last 64 orbit samples exceed a predefined threshold an operator alarm is raised and the DSP software disables the possibly faulty BPM. Since the orbit feedback monitors the on-line status of all BPMs it automatically recalculates the inverse response matrix of the remaining set of BPMs and correctors and continues operation automatically. The next step in the implementation of the FOFB system is to shift the functionality of the SOFB from the central beam dynamics PC down to the DSP level and operate the feedback with initially 3 Hz before switching to the full sample rate of 4 kHz.

Figure 5: Hardware layout of the FOFB in one of the twelve sectors