| It is important to represent the spectrum of emitted neutrons as realistically as possible due to their importance for shielding, activation, and fission. Small emission probabilities for low-energy neutrons may acquire increased importance due to the large cross sections at low energies. However, many modern evaluations are done with nuclear model codes that represent emission in energy bins (that is, histograms). Direct use of such calculations would severly distort the effects of emitted neutrons (although the representation would be reasonable for emitted charged particles). In such cases, the evaluator should fit a realistic evaporation shape to his low-energy neutron emissions and use this shape to generate additional points for the energy distribution. |
See ENDF102, Section 6.3.4.
Supplementary Note:
| The limiting energy dependence at low emission energies is sqrt(E') in either CM or LAB. The Jacobian of the transformation from the CM to the LAB is just Sqrt(E'LAB/E'CM). This shows why a reasonable energy dependence for the emissions in the CM is important to get good results for the laboratory distributions. |