Neutron radiography with isotropic illumination by diffuse source

The idea of this article is to use an isotropic illumination of a sample by thermal neutrons instead of a collimated beam for imaging purposes. The standard experimental setup is rearranged: the inspected object is placed to an isotropic field of slow neutrons and observed by a pinhole camera with an imaging neutron detector. A fraction of neutrons scattered inside of the inspected sample can pass through the pinhole and reach the detector. Images created by this method are similar to the standard photography. The regions with larger cross-section for neutron scattering are highlighted in the acquired images. A compact experimental system has been designed. The system consists of a semiconductor pixel detector Medipix2 (14times14 mm, 256times256 pixels) adapted for neutron detection, a pinhole collimator and a sample holder. The entire system is placed inside a shielded waterproof box. The neutron shielding was optimized using Monte-Carlo simulations. The first experimental results measured in the active zone of the research nuclear reactor LR-0 at Nuclear Research Institute in Rez near Prague are presented