A spectrometer for lifetime determination by β-γ-γ delayed coincidence technique at KUR-ISOL

A new spectrometer for measuring nuclear level lifetimes has been installed at the on-line isotope separator of the Kyoto University Reactor. The spectrometer consists of a LaBr3(Ce), Ge and a thin plastic scintillation detector, and the lifetimes are determined using a β-γ-γ delayed coincidence technique. In this study, the LaBr3 detector was used to obtain time spectra, whereas the Ge detector was used to select a desired γ branch. The energy dependence of the time resolutions was measured down to a photon energy of 100 keV. The lifetimes measured for the excited levels in 93Sr and 148Ce agree well with their evaluated values. The lifetime of 8.5(5) ns was obtained for the first time for the 98.2 keV level in 148Pr.