Evaluation and Application of an Improved Slit Probe for the X-Ray Secondary Emission Spectrometer

Abstract

AbstractX-ray probe accessories for commercial flat-crystal X-ray secondary emission (fluorescence) spectrometers have consisted of pinhole apertures in the primary or secondary X-ray beam. The smaller the aperture the lower the intensity, and apertures having diameters less than approx. 0.1 mm are of real value only for relatively high concentrations of elements having intense spectral lines.There are two practical methods for increasing the intensity obtained with small apertures. One method is use of curved crystals ; it is applicable to any type of sample. The other method m use of a slit instead of a pinhole. It is limited to samples such as long linear inclusions ; sections of coated surfaces, diffusion couples, and metal-to-metal and metal-to-ceramic interfaces; and other layered structures where composition varies in a direction normal to the layers, but not along any one layer. The slit also has several other disadvantages that do not apply to the pinhole. However, when used with samples of the proper type, the slit has two outstanding advantages : Increased sensitivity and statistical precision are realized by replacing a pinhole of a given diameter with a slit of the same width ; alternatively, improved resolution is realized without loss of intensity by replacing the pinhole with a slit of smaller width. Moreover, the slit can be installed on a commercial X-ray spectrometer quickly and conveniently, and often allows useful X-ray probe work to be done on samples for which pinhole apertures would be inadequate.A slit probe of the type already described by the writer has been improved and evaluated on a General Electric X-ray spectrometer equipped with a curved crystal. The improved accessory has been applied to studies of several metal-tometal and metal-to-ceramic systems. Some of these studies are discussed in detail.