“…Although prompt gamma-rays emitted from Cd are used in the KUR slow positron beamline to enhance the quantity of positron creation, the use of other materials having large neutron-capture cross sections is also worth consideration [17,35,36]. The 157 Gd(n,γ) 158 Gd, 155 Gd(n,γ) 156 Gd, and 149 Sm(n,γ) 150 Sm reactions may be effective, since the neutron-capture cross sections of 157 Gd, 155 Gd, and 149 Sm have large values of 254000 barns, 60900 barns, and 40140 barns, respectively [25].…”