Systematics in Differential Thick-Target Neutron Yields Parameterized by Moving Source Model

Abstract

Applications of accelerators to fields other than nuclear physics have been increasing more and more. As the fields expand, a greater variety of ions with wider accelerating energies are being used in these accelerator facilities. The thick-target neutron yield (TTNY) is the base data used for the shielding design as well as for the application of these accelerator facilities to estimate the neutron production rate in the facilities. However, so far, very few data of differential TTNY have been measured except for protons. Even for alpha particles, the number of measurements is not enough. Because of the lack of measured data, a study on TTNY for heavy ions has not been done. A practical calculation method for estimating the data for heavy ions has still not been established. Here, generalized parameterization of the differential thick-target neutron yield (TTNY) is obtained by studying systematics in the differential TTNY based on moving source parameters deduced from experimentally obtained differential TTNYs for light and heavy ions. The yields of equilibrium neutrons (ENs) and nonequilibrium neutrons (NENs) are expressed by simplified expressions. The variation of the nuclear temperature of the EN is scaled with the excitation energy transferred to the target-like fragment. The nuclearmore » temperature of the NEN is reproduced fairly well by the Fermi gas model. The scaling of the velocity parameter of the EN is considered based on the breakup fusion mechanism. The velocity of the NEN component is compared with the corresponding data for the proton emission. The velocity is related to the relative speed between projectile and target nuclei at contact.« less