Intense Gallium X-Rays for Microradiography and Diffraction Investigations

Abstract

THE identification of segregates in ferrous and non-ferrous alloys by the technique of microradiography^1–4 is now established as an extremely valuable complement to the conventional optical micrographic procedures. The contrast between segregate and matrix is independent of the etching characteristics of the metal, but depends, instead, on the relative absorption of the X-ray beam through a finite depth of specimen. Since the linear absorption coefficient μ is C. N⁴ρλ³, where N is the atomic number of the absorbing element, ρ its density, λ the wave-length of X-rays and C a constant between absorption edges, it follows that, provided suitable wave-lengths are available, a segregated element may be positively identified by X-ray methods alone. When it is sought to distinguish between two elements close to each other in atomic number, it is possible to accentuate the contrast in X-ray absorption by choosing a radiation with a wave-length lying between the K-absorption edges of the elements.