The Los Alamos model of neutron emission in fission

Theoretical representations of two of the observables in prompt neutron emission in fission are given, namely, the prompt fission neutron spectrum N(E) and the average prompt neutron multiplicity <(nu)over bar>(p). Early representations of these observables are presented and their deficiencies are discussed. This is followed by a description of the Los Alamos model for the calculation of the two quantities. Emphasis is placed upon predicitability and accuracy. In particular, the dependencies of N(E) and <(nu)over bar>(p) upon the fissioning nucleus and its excitation energy are treated in detail. Recent work in the calculation of the prompt fission neutron spectrum matrix N(E, E-n), where E-n is the energy of the neutron inducing fission, is then discussed. Concluding remarks address the current status of our ability to calculate these observables with confidence, the direction of future theoretical efforts, and limitations to current (and future) approaches.