Two detectors of anti-protons. At left is the arrangement Segre's group used successfully in 1955. M indicates bending magnets, Q focusing quadrupole magnets, S scintillation counters and C Cerenkov counters to eliminate false counts. At right is the Lofgren group's detector that analyzed the. beam from Segre's magnets. The small Cerenkov counters distinguished the antiproton from a meson, the large one registered the annihilation of an antiproton with a proton.