| Energy spectra calculations have been refined for the low energy (e.g. <2.5 MeV) neutron continuum produced in the alpha + Be reaction. As expected, new distributions shift neutrons to maxima <1 MeV, and support previous assertions that the continuum is the result of a sequential three-body decay process. Appropriate kinematic descriptions were added to the SOURCES computer code thus providing for the first time a simple algorithm to include a break up reaction. Difficulties associated with spectral calculations are discussed and three calculations are compared to experimental data for AmBe, PuBe, and PoBe neutron sources. This work represents a new tool to predict neutron energy spectra in the lower energy regime and, upon submission to the Radiation Safety Information Computational Center, the code distributor, will ultimately upgrade SOURCES from version 4C to 5A. |
