  A system for bunch-by-bunch detection of transverse proton and antiproton
coherent oscillations in the Tevatron is described. It is based on the signal
from a single beam-position monitor located in a region of the ring with large
amplitude functions. The signal is digitized over a large number of turns and
Fourier-analyzed offline with a dedicated algorithm. To enhance the signal,
band-limited noise is applied to the beam for about 1 s. This excitation does
not adversely affect the circulating beams even at high luminosities. The
device has a response time of a few seconds, a frequency resolution of 1.6e-5
in fractional tune, and it is sensitive to oscillation amplitudes of 60 nm. It
complements Schottky detectors as a diagnostic tool for tunes, tune spreads,
and beam-beam effects. Measurements of coherent mode spectra are presented to
show the effects of betatron tunes, beam-beam parameter, and collision pattern,
and to provide an experimental basis for beam-beam numerical codes. Comparisons
with a simplified model of beam-beam oscillations are also described.
