An experiment has been prepared and performed to prove the feasibility of creating anisotropic structures in which surfaces of thermal-neutron sinks are formed with the subsequent concentration in selected areas. A device capable of selecting neutrons by the direction in space is based on the effect of neutron reflection from the surface of materials. Experimental confirmation has been obtained for the operability of a neutron concentrator design in devices that form and use directed high-intensity thermal-neutron beams with elliptical-profile channels. The neutron concentrator is made of blocks of profiled-graphite and aluminum plates. The operability of a slowing-down and focusing structure (SFS) based on a package of elliptical neutron mirrors has been experimentally verified. The SFS is able to form oriented thermal-neutron beams from the outgoing flow of reactor neutrons. Silicon single-crystal wafers are used, with which it is possible to obtain distributions of integral neutron fluxes in a reactor to detect the effect of selective thermal-neutron separation. The experiments have been carried out in the GEK-4 channel at the IRT-T reactor of the National Research Tomsk Polytechnic University with an integral neutron flux of (2.30−3.02) × 1017 cm−2. The neutron flux is determined from the change in the electrical resistivity of single-crystal silicon wafers. The effect of the thermal-neutron concentration has been detected both on a block of graphite neutron mirrors and on a block of thin-walled aluminum elliptical mirrors.

S. N. Stolbov

Papers

Anisotropic Structures for Concentrating Thermal-Neutron Fluxes