Effect of axial reflector on radial uniformity in neutron transmutation doping of silicon

Significant axial variation of radial uniformity is observed in Si-ingot neutron transmutation doping in the flux screening method, and leads to non-uniform resistivity distribution for a certain part of Si-ingot. This axial variation of radial uniformity is caused by the installation of a partial neutron screen which decreases the reaction rates differently in the center and surface at the region not surrounded by the partial neutron screen. For the improvement of the specific distribution of radial uniformity in the axial direction, a new concept of axial reflector is introduced to partly change the reaction rate at a certain region of Si-ingot, and neutron irradiation experiments are carried out at the heavy water neutron irradiation facility in the Kyoto University Research Reactor. Based on the experimental and numerical results, the new axial reflector is proved to be effective for improving the axial variation of radial uniformity.

► The axial variation of radial uniformity in a Si-ingot of NTD is caused by the partial neutron screen.
► A new concept of axial reflector is introduced to improve the axial variation of radial uniformity.
► Effect of a new axial reflector is investigated through the neutron irradiation experiments.
► The new axial reflector is proved to be effective to improve the axial variation of radial uniformity.