After the final nearly 90 degree bend, the proton beam extracted from the main ring is focused on a 60cm long alminum target which is a part of the first magnetic horn. The horn is designed to focus positively charged pions that are produced at the target efficiently together with the second horn that immediately follows the first while defocusing negatively charged particles.

Between the second horn and the entrance of the decay pipe there is space reserved for two devices: a pion monitor and a phi-asymmetry monitor.

The pion monitor is a gas Cherenkov detector that is designed to measure the angular and momentum distributions of the secondary pions assuming that the distributions are symmetric in phi with respect to the beam axis.

The phi-asymmetry monitor is made of a pair of ionization chamber arms attached on a wheel which rotates around its axis parallel to that of the beam. Because of its shape and its use of ionization chambers, it is dubbed as "Ionocopter". As the name suggests, it can measure the flux of charged particles, most of which are charged pions, as a function of the phi around the beam axis and the radial distance from the beam axis.

These two devices together with the muon monitors right after the beam dump provide vital informtion about the neutrino beam so that we can tune the beam simulation code.