BPMs monitors sense the passage of the beam when it induces a signal in the pickup electrodes mounted in the beam waveguide. This induced signal is of low current but can be 10's of volts for several nanoseconds, in synch with the beam's arrival. This signal is put directly on to a high quality coax to the receiving electronics.
In addition to this readback pulse, the BPM generates a calibration pulse that is sent to the electrodes to simulate a beam in a quantified manor. This is a low level signal in synch with the beam rep rate, but out of phase with the beam itself.
BPM acquisition electronics is similar to other VME/Motorola PowerPC racks except for a high speed digitizer which will clock at approximately 100MHz. this is an internal clock to the ADC board and should not be able to propagate out of the VME chassis.
