Yield of Neutrons per Interaction in U, Pb, W, and Sn by Protons of Six Energies between 250 and 900 Mev Selected from Cosmic Radiation

The production of low-energy neutrons in U, Pb, W, and Sn by protons of six selected energies between 250 and 900 Mev has been measured using cosmic radiation as a proton source. The protons were selected and their energy measured by a vertical counter telescope containing three Cerenkov detectors which employed liquid nitrogen, water, and Plexiglas as radiating media. The protons interacted in 22 and 44 g ${\mathrm{cm}}^{-2\mathrm{}}$ thick slabs of the target elements, and the neutrons produced were detected in a 4-foot cubic paraffin moderator, ${\mathrm{B}}^{10}$ ${\mathrm{F}}_3$ counter assembly placed below the proton selecting telescope. The principal body of data was obtained at 3260 m altitude; a series of runs at 150 m was made to check the high-altitude data for muon contamination of the selected protons.