Energy response of Bonner spheres to neutrons in parallel beam and point source geometries

The energy response of the multisphere system equipped with a 3He proportional counter was calculated by means of the adjoint flux technique. Calculations were performed using the one-dimensional, discrete ordinate neutron transport code ANISN and the DLC-47 cross section library. The effect of the angular distribution of the impinging neutrons in the so-called 'point source' geometry was studied. In current correction procedures, this effect is expressed only as a function of the ratio of the sphere radius and source-to-sphere distance. This study shows additional pronounced dependencies on both neutron energy and sphere size. (orig.)