Beam Position 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 stripline BPM system generates a calibration pulse that is sent to the striplines to correct for signal gain variation and drift. This is performed between beam pulses.
LCLS Stripline BPM Processor Engineering Specification (DRAFT)
LCLS BPM Data Acquisition System WPPB40
2022 SLACPAS Steve Smith BPM Talk Slides
LCLS BC1 rectangular BPM, beam left to right
LCLS-II undulator hall cavity BPM
LCLS-II cavity BPM electronics in Building 913 BPM MPS Interlocks
LCLS Cavity BPM Receivers Network Information
