HIGH-ENERGY GAMMA-RAY PRODUCTION IN PROTON-INDUCED REACTIONS AT 104, 145, AND 195 MEV

Energy spectra and angular distributions have been measured for high energy gamma rays (E-gamma greater-than-or-equal-to 20 MeV) from proton-nucleus reactions at 104, 145, and 195 MeV on targets of C, Zn, and Pb. Gamma rays were observed with energies up to 170 MeV. The spectra showed differences from the typical exponential shape that is observed in gamma ray production from heavy-ion reactions. The angular distribution of the gamma ray is forward peaked in the laboratory, which is consistent with emission from a moving source. A comparison is made with previous measurements at 72, 140, 168, and 200 MeV. The experimental evidence indicates that first-chance incoherent proton-neutron bremsstrahlung is the main production mechanism.