Poly-capillary lens for neutrons

It is experimentally shown that when slow neutrons are focused, in the lens focal plane halo is produced by both slow and fast neutrons, as well as hard photon radiation. The ratio of fluences in the lens focus and in the halo is determined by the spectral structure of radiations of the neutron source used and properties of the lens and its shielding. iguration is suggested of a neutron lens, iteratively suppressing fluences of halo background radiations. ectral structure and spatial distributions of neutron fluxes in the focal planes of a conventional half-lens and of the lens of suggested configuration have been experimentally studied.