  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. The beam must be steered with 1 mRad angular accuracy toward the Soudan
Underground Laboratory in northern Minnesota. 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. We review how the monitors will be used to make beam quality
measurements, and as well we review chamber construction details, radiation
damage testing, calibration, and test beam results.
