Übergangskern

Übergangskern is a German term that translates to "transition kernel" in English. It is primarily used in the context of nuclear physics and nuclear engineering, particularly in the study of nuclear reactors and neutron transport. The Übergangskern describes the probability that a neutron, after undergoing a scattering event, will be emitted with a specific energy and in a particular direction.

More formally, the Übergangskern is a function that characterizes the angular and energy distribution of scattered neutrons. When a neutron interacts with a material, it can be elastically or inelastically scattered. Elastic scattering involves the transfer of kinetic energy between the neutron and the nucleus, while inelastic scattering results in the excitation of the nucleus, and the neutron loses more energy. The Übergangskern quantifies these post-scattering properties.

In neutron transport calculations, the Übergangskern is a crucial component of the neutron transport equation. It allows for the accurate simulation of how neutrons propagate through a reactor core or other nuclear material. By understanding the scattering properties, which are encapsulated by the Übergangskern, engineers can predict neutron flux distributions, reaction rates, and ultimately the criticality and safety of nuclear systems. The precise form of the Übergangskern depends on the specific material and the incident neutron energy.