The use of the Polychromator (multichannel spectrometer) for X-ray analysis allows choice of the optimum combination of slit width, crystal type, focussing circle radius and detector for each of the elements to be determined by the instrument.

Comparisons will be made of various curved and ground crystals such as quartz, lithium fluoride, sodium chloride and ADP used in a focussing spectrometer. The effect of the width of the entrance and exit slits upon resolution, line intensity and line-to-background ratios will be discussed. Gas filled detectors such as Multitrons, flow proportional counters and Geiger counters will be discussed as to the effect of the filling upon efficiency and upon their use with counting or integrating techniques. Limits of detectability for various elements with optimum combinations of the above components will be reported.