The collapsed cross-sections, reaction rates depend strongly on the nature of the projectile spectra, and so it is important to use the appropriate spectrum together with the appropriately-weighted cross-section data. With the advances of modern simulation software and high-resolution spectra the user is reminded of the importance of the tails, low or high-energy ones, on the reaction rates.
The majority of neutron-application spectra stem from light-water assemblies, mock-ups, piles or reactors where the integral responses are strongly, if not solely, influenced by the energy ranges of the fission spectra, resonance range and thermal Maxwellian. Fusion spectra that have been obtained from magnetic confinement (MCF) or inertial confinement fusion (ICF) present typical D-D 2.5 MeV, or D-T 14 MeV peaks sometimes accompanied by a higher-energy tail, but also showing rather different slowing-down profiles. Accelerator-driven beam spectra are important in their role in nuclear data acquisition and materials research, but also for medical therapeutic and diagnostic applications. [More..]
In essence, the particle spectrum profile, through the collapsing process, emphasises the energy region of most importance for the application. Transferring data from one application or energy range to another should be done with great care as it can easily lead to misleading and inappropriate numerical results.
Several incident particle spectra are provided in the table below, mostly including neutron incident spectra but with some charged particle spectra. Note that these are provided in the original energy group structures as generated by the code(s) that calculated them. These are often not the same energy group structures as those provided for the nuclear data libraries and may require a flux conversion. Note that while the group conversion can easily be performed, this cannot add structure when moving from a coarse group structure to a more refined multi-group.
