Epithermal neutron self-shielding factors in foils for collimated beams.

An epithermal neutron self-shielding factor must be introduced to take into account the absorption of a neutron beam crossing a sample. This factor depends on the geometry and dimension of the sample, as well as on the physical and nuclear properties of the nuclides. On the basis of a dimensionless variable, which includes the relevant characteristics of the sample, universal curves for monoenergetic and 1/E collimated neutron beams are proposed, which enable the determination of the self-shielding factor for isolated resonances of high absorber nuclides.