Design and Application of X-ray Emission Analyzers Using Radioisotope X-ray or Gamma Ray Sources

This paper reviews the present state of development and application of X-ray emission spectrometry using radioisotope X-ray and gamma ray sources for excitation, and energy discrimination and dispersion techniques for spectrum analysis. The design and use of instrumentation is characterized by the choice of one of the two main methods of energy selection now employed. The balanced filter method is simple but restricted to sequential determinations of single elements and so finds its main use in small, hand-portable, battery-operated analyzers for field, laboratory, or industrial use. Energy dispersion with high resolution silicon or germanium detectors permits simultaneous collection of the whole excited spectrum and so promises rapid multielement analysis. Available equipment is more suited to laboratory conditions. Relevant components of radioisotope X-ray spectrometers are described. Emphasis is placed on source-specimen-detector configurations, sources, source-target assemblies, absorption edge filters, and relevant properties of detectors. Equations for estimating the feasibility of a given analysis are derived, and interferences due to absorption, enhancement, and heterogeneity effects are discussed. A major portion of the paper is devoted to a review of published applications and covers elemental analysis from aluminum to uranium, and measurement of coating thickness. References are made where appropriate to available portable, industrial, and laboratory instruments.