Design and implementation of a compact analog Constant Fraction Discriminator for high-resolution timing in gamma-ray spectroscopy

Abstract This work presents a custom analog front-end card designed for the read-out of PMTs coupled to lanthanum bromide scintillators. It integrates 16 discrete analog constant fraction discriminators (CFDs) on a compact 12×10 cm board, providing precise timing information for nuclear lifetime measurements. The design emphasizes cost-effectiveness, utilizing off-the-shelf discrete components, as well as compactness, achieved by using miniature coaxial connectors and cables as delay elements. The focus of this paper lies on the unusual and extremely minimalist analog shaper/discriminator design which is devised without operational amplifiers, making use of only a handful of RF transistors and LVDS receivers in place of comparators.