Experiences of the QSBPM system on MAX II

The MAX II is a third-generation synchrotron radiation source. The first beamline is in operation and several others are in the commissioning phase. The storage ring is equipped with a Quadrupole Shunt BPM (QSBPM) system for in situ calibration of the button-pickup BPM system. The calibration system uses switchable shunts on the combined-function quadrupole-sextupole magnets to find their magnetic centers. The BPM system has a time constant of several seconds, so a switched system is the only possibility. Each BPM pickup head and its corresponding electronics have been calibrated with the QSBPM system. The system has been in operation for about two years and operational experience, together with the technique itself, is discussed. The quadrupole shunts that are a part of the QSBPM system are, together with a spectrum analyzer and a tracking generator, also used to measure the beta functions individually in all main quadrupoles of the machine.