A high sensitivity tune measurement system for BEPCII

BackgroundThe tune is one of the most important parameters of the storage ring which play a crucial role in the brightness optimization. The synchrotron radiation will suppress the oscillation and make the detection unusual difficulty without any kicker excitation.
PurposeA new high sensitivity tune measurement system is developed to show the real-time tune during the colliding.
MethodPeak diode detectors are used to convert short beam pulses from a button BPM into slowly varying signals. Their DC components, constituting a large background related to beam offsets, are suppressed by series capacitors, while the small signals related to beam oscillations are passed to the subsequent stages for amplification and filtering.
ConclusionA direct diode detection technique based on the diode peak hold circuit could increase the sensitivity by hundreds time which gets a clearly tune peak even with synchrotron radiation and bunch-by-bunch feedback damping.