Two-parameter pulse height analysis in liquid scintillation. Chapter 5

Virtually all liquid scintillation spectrometers since 1950 have utilised dual-phototube coincidence detectors to reduce background count rate. Various methods of combining the output signals from each detector have been used for pulse height discrimination against background. This chapter shows how analysis of the relative pulse height from each detector is utilised to provide additional information about the sample specimen and photo-detectors. Two-parameter pulse height analysis is used to examine the relative response from each photodetector. Correlations between the response from each detector are used to resolve some of the ambiguities which arise in single-parameter observations. The added dimension provides a new means of discriminating between background events and those caused by scintillations in the sample, by rejecting regions of the 2-parameter plane. Various transformations of the 2-parameter spectrum into a single-parameter spectrum to improve background discrimination, spectral resolution and/or efficiency are described. (author)