GIANT-DIPOLE RESONANCE NEUTRON YIELDS PRODUCED BY ELECTRONS AS A FUNCTION OF TARGET MATERIAL AND THICKNESS

This paper characterizes the functional dependence of the Giant Dipole Resonance neutron yield produced by electrons in terms of the atomic number (Z) and thickness (T) of the target. The yields were calculated by integrating, over the photon energy, the product of the differenti al photon track length and published photoneutron cross sections. The EGS4 Monte Carlo code and analytical formulas were used to calculate t he differential photon track length. In thick targets, the Giant Dipol e Resonance neutron yield approaches a saturation value as target thic kness T increases to 10 radiation lengths. A formula, 8 x 10(-6) x (Z( 1/2) + 0.12 Z(3/2) - 0.001 Z(5/2)) n electron(-1)Mev(-1), developed fr om EGS4 calculations, estimates thick-target neutron yields for incide nt electron energies E(0) above 50 MeV. Giant Dipole Resonance neutron yields, calculated by several analytic formulas for the differential photon track length, are compared with EGS4 calculations. Modification s to the analytic formulas are suggested. A scaling function is derive d to estimate, from the thick-target formula, neutron yields produced in thin targets.