The Angular Distribution of Thermal Neutrons at the Surfaces of Black and Grey Cylinders

Angular distributions of thermal neutrons at the surfaces of cadmium and copper cylinders were measured by activating directionally sensitive detectors. Comparisons of the experimental data with the theoretical predictions of the distributions were made by the “optical path method,” using a radial flux distribution either calculated with the THERMOS code or measured. Experimental points agree within ±3% with the predicted values given by the measured fine structure, corrected for the shadowing effect due to the collimator, and are about 10% lower than the values predicted by the THERMOS radial flux. The results give some information on the analytical form of the angular flux in the different regions of observation.