COMBINED NEUTRON SCATTERING, NEUTRON CAPTURE GAMMA RAY AND POSITRON ANNIHILATION STUDIES ON MATERIALS UNDER ELASTIC AND PLASTIC DEFORMATION

ABSTRACT Nondestructive characterization of residual stresses in materials by neutron time-of-flight using a novel correlation technique has been supplemented by a high-resolution gamma ray spectrometer to detect radiation from prompt neutron capture simultaneously with the stress measurement. Sensitivities and detection limits for important alloy constituents from characteristic gamma ray spectral lines as well as the composition of a number of alloys have been determined by this method. It can also be used for nondestructive determination of hydrogen contents. The interaction of the high-energy capture radiation with the material generates electron-positron pairs. Positron annihilation radiation is thus produced with intensities sufficiently high to investigate dislocation densities from plastic deformation.