Long-Wavelength Neutron Transmission as an Absolute Method for Determining the Concentration of Lattice Defects in Crystals

Abstract

The scattering of long-wavelength neutrons by lattice defects has been used to measure in an absolute way the number of isolated interstitial atoms and vacancies introduced in graphite by reactor irradiation. For an exposure of 1.1×${10}^{20}$ neutrons/${\mathrm{cm}}^2$ the fraction of displaced atoms was found to be 0.0263. This value is more accurate than present theoretical estimates largely because of uncertainties in exposures. Within this limitation the experimental value is in excellent agreement with that derived from Seitz's theory.