Determination of the differential cross section for the reaction X(p,n)Y using 800 MeV proton bombardment of Al, Cu, In, Pb, and U

The energy- and angle-dependent differential cross sections for the reaction X(p,n)Y have been determined by bombarding thin targets of Al, Cu, In, Pb, and U with 800 MeV protons. Neutron spectra were measured by using the time-of-flight technique and an NE-213 liquid scintillator which was calibrated over an energy range of about 0.5 to 800 MeV. The spectra were measured at angles of 00, 300, 450, and 1120 relative to the proton beam. The cross sections reveal a strong angular dependence for the neutrons produced with energies greater than about 20 MeV. The angular dependence of the cross sections below about 20 MeV appears to be anisotropic in both the laboratory and zero-linear momentum (ZLM) rest frames. The backward peaking of cross sections below about 1 MeV in the ZLM coordinate system indicates the backward motion of the recoil nucleus during evaporation. The effect of this motion on the cross sections in the laboratory rest frame is seen as an energy shift in the spectra as the detection angle increases, most noticeably for the Al and Cu targets. We have compared our X(p,n)Y data with Monte-Carlo code predictions; in particular, we compared the energy distributions of the measured and calculated double-differential neutron-production cross sections. At each angle, we also compared the integrals of the differential cross sections over the available energy range