Selectivity of X-Ray Detection by a Variable Geometry Proportional Counter

Abstract

THERE are two reasons for the growing interest in the generation of characteristic X-rays by heavy particle bombardment¹ as opposed to electron irradiation. The resultant X-rays are virtually free from white background radiation, so that even the lightest elements can be detected; and the technique can be allied to the phenomenon of channelling to yield a tool for locating the lattice positions of foreign atoms in crystalline systems². The gas-flow proportional counter is indispensable for detecting the resultant X-radiation because the solid state detector, whilst offering superior resolution, is currently incapable of detecting X-rays of energy lower than 1 keV; thus all elements of atomic number below sodium cannot be identified. Furthermore, even with heavy elements it is often more useful to detect the softer X-ray component, which is produced in greater abundance.