Measurement of the Angular Distribution of Thermal Neutrons at the Surfaces of Cadmium Rods

The angular distribution of thermal neutrons was measured at the surfaces of cadmium bars in the graphite core of the Physical Constants Test Reactor (PCTR) at Hanford. The distribution was obtained by activating dysprosium detectors placed at the bottom of small holes in the cadmium. Theoretical calculations of the distributions were made with the optical-path method and with two versions of the S_N method: HAPO Program S and the Los Alamos DSN code. All methods agreed to within the 3% standard deviation of the measurements.