  The Neutrinos at the Main Injector (NuMI) beamline will deliver an intense
muon neutrino beam by focusing a beam of mesons into a long evacuated decay
volume. We have built 4 arrays of ionization chambers to monitor the neutrino
beam direction and quality. The arrays are located at 4 stations downstream of
the decay volume, and measure the remnant hadron beam and tertiary muons
produced along with neutrinos in meson decays.
