Thermal cross section libraries for neutron filters

Here we present new thermal cross section libraries for sapphire and silicon, materials that are usually used as neutron filters in neutron facilities with thermal beams. Due to the lack of these thermal cross section libraries, calculations performed in order to optimize beams for specific applications are based on the "free gas" approximation. Debye model was used in both cases to represent the vibrational frequency spectra required to feed NJOY nuclear data processing system in order to produce the corresponding libraries in ENDF and ACE format. These libraries were validated with experimental data available, some from the literature and others obtained in the pulsed neutron source at Centro Atómico Bariloche. Good agreement is reached what confirms the usefulness of using the Debye temperature as a single parameter to represent the lattice dynamics in solids, for generating cross section libraries necessaries to be used in design and optimization of auxiliary components of nuclear facilities. (author)