The development and application of the phosphor-photomultiplier combination to the detection and spectrometry of low energy quanta

Abstract

Although the phosphor-photomultiplier combination provides an instrument of great versatility, up to quite recent times it has been employed almost solely in the nuclear physics field. This thesis describes some experiments designed to determine the effectiveness of the device for the detection and spectrometery of low energy X-ray quanta such as are employed in X-ray diffraction work. The present experiments were all carried out using Copper K radiation (8keV). A coincidence pair was the principal experimental arrangement investigated, as this provided a means of greatly reducing the number of dark noise pulses. A two channel pulse height analyser was devised to enable the distribution of the total number of photoelectrons released in each scintillation to be determined. The single phototube counter was also investigated and the results obtained confirm its practibility for X-ray diffraction work provided photocathodes of high quantum efficiency (15% at least) are employed. Diffractometer records are included which illustrate the practical performance of both the single and coincidence counters. The absolute accuracies of the measurements made throughout these experiments are relatively poor since practically no calibrated test instruments were available at any stage of the project. However, the satisfactory overall performance of the equipment is evidenced by the diffractometer records which generally are aS good, if not better, than those obtainable on commercial instruments employing conventional detectors.