  We have conducted tests at the Fermilab Booster of ionization chambers to be
used as monitors of the NuMI neutrino beamline. The chambers were exposed to
proton fluxes of up to 10$^{12}$ particles/cm$^2$/1.56$\mu$s. We studied space
charge effects which can reduce signal collection from the chambers at large
charged particle beam intensities.
