Photoproton and Photoneutron Production in Aluminum and Copper

Abstract

The ratio of proton to neutron yields from aluminum and copper irradiated with betatron x rays up to 20.8 Mev in energy has been measured. Simultaneous detection of protons and neutrons is accomplished by placing two samples of the same element in series in the x-ray beam. Direct detection methods are used in each case, a shallow proportional counter for protons and a boron-lined detector for neutrons. A photon difference method has been used to reduce yield data to cross-section form. The proton and neutron yields for aluminum are found to be approximately equal at 20 Mev with cross sections of 19 and 21 millibarns, respectively. At 20.8 Mev a yield ratio of one proton to about 6 neutrons is found for copper, with a peak photoproton cross section of 23 millibarns. The results are compared to a calculation based on the assumption that these reactions proceed through the formation of a compound nucleus.