Measurement of thermal neutron waves at high frequencies in BeO

Abstract

The amplitudes and phases of neutron waves have been measured in a BeO assembly in the frequency range 515.7 Hz. The results confirm earlier measurements that below ~ 520 Hz the neutron wave has the properties of a discrete mode of propagation. At frequencies > 720 Hz the attenuation α(z) and phase shift parameters ζ(z) change with distance from the source, the change being more marked the higher the frequency. The observed spatial variations of α(z) and ζ(z) do not agree with present theoretical predictions. Interference effects predicted by theory have not been observed.