The use of the Geiger - Miiller counter X - ray spectrometer in an X - ray laboratory , with special reference to automatic recording

The advantages and limitations of Geiger counter techniques in a laboratory applying X-ray methods to a variety of problems are discussed and some simple examples are described. These illustrate the convenience of its use in obtaining semi-quantitative results very rapidly and in following the effects of various treatments. The accuracy of the method is considered in relation to the statistical effects associated with the operation of the Geiger counter and the influence of damping in the recording system. The addition of Geiger-Muller counting devices to X-ray equipment has placed at the disposal of the investigator a means of directly and rapidly estimating X-ray diffraction intensities which he has not possessed since the early ionization chamber technique was generally discarded in favour of the photographic record. Several years' experience with the new technique at the National Physical Laboratory has made it evident that Geiger-Muller counter apparatus has a definite part to play in an X-ray laboratory and that for dealing with certain kinds of problem it has marked advantages over the photographic procedures. The following example is typical of the more straightforward forms of application. A request was received for the examination of six metallic specimens, all somewhat dirty or oxidized, each of which was stated to consist of an iron base with a plated surface layer, probably nickel. The problem was to determine as rapidly as possible whether all the specimens were in fact plated with nickel. One of the specimens was immediately mounted on a Geiger-Muller counter X-ray spectrometer, and on the assumption that nickel diffraction lines would be found, a manual traverse was made over the range 28 = 70"-40" at a rate of approximately 1" in 10 sec, using unfiltered iron radiation. The pen of the automatic recorder was switched on at the same time, but its chart remained stationary, and so long as no diffraction line was encountered, the pen suffered a small deflexion corresponding to background intensity and remained stationary upon the chart except for slight movement due to the natural fluctuations of the counts emerging from the Geiger-Muller counter tube. As soon as a diffraction line was encountered, however, an increasing deflexion was observed, and the effective position and intensity of the line was then determined in a few seconds by successively narrower bracketing traverses across the peak and the angle written down. The chart was then moved forward by hand to a new …