Browsing Radiocarbon, Volume 34, Number 1 (1992) by Authors
Liquid Scintillation Counter Characterization, Optimization and Benzene Purity CorrectionMcCormac, F. G. (Department of Geosciences, The University of Arizona, 1992-01-01)In liquid scintillation counting (LSC), small variations in benzene purity can cause 14C pulse-height spectra to move with respect to the counting window. Thus, one must carefully monitor the purity of each benzene sample and apply corrections for spectral shifts. I describe here the techniques used at Queen's University Belfast for deriving correction factors for observed small variations in benzene purity. I also describe the methods used at our laboratory to fine-tune our Quantulus LS counters for high-precision dating. The tuning of the instruments minimizes the effect of fluctuations in gain that may occur during the long counting periods required for high-precision dating. Any remaining influences on efficiency owing to gain changes are corrected for, along with the purity correction, by continuous monitoring of the spectrum produced by the external source.