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The Generalized Centroid Difference method for lifetime mesaurements via $\gamma$-$\gamma$ coincidences using large fast-timing arrays

Abstract : A novel method for direct electronic "fast-timing" lifetime measurements of nuclear excited states via γ-γ coincidences using an array equipped with N very fast high-resolution LaBr3(Ce) scintillator detectors is presented. The generalized centroid difference method provides two independent “start” and “stop” time spectra obtained without any correction by a superposition of the N(N − 1)/2 calibrated γ-γ time difference spectra of the N detector fast-timing system. The two fast-timing array time spectra correspond to a forward and reverse gating of a specific γ-γ cascade and the centroid difference as the time shift between the centroids of the two time spectra provides a picosecond-sensitive mirror-symmetric observable of the set-up. The energydependent mean prompt response difference between the start and stop events is calibrated and used as a single correction for lifetime determination. These combined fast-timing array mean γ-γ zero-time responses can be determined for 40 keV < Eγ < 1.4 MeV with a precision better than 10 ps using a 152Eu γ-ray source. The new method is described with examples of (n,γ) and (n,f,γ) experiments performed at the intense cold-neutron beam facility PF1B of the Institut Laue-Langevin in Grenoble, France, using 16 LaBr3(Ce) detectors within the EXILL&FATIMA campaign in 2013. The results are discussed with respect to possible systematic errors induced by background contributions.
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http://hal.in2p3.fr/in2p3-01077155
Contributor : Michel Lion <>
Submitted on : Friday, October 24, 2014 - 9:45:18 AM
Last modification on : Friday, September 10, 2021 - 1:50:11 PM

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J.-M. Régis, J. Jolie, H. Mach, G.S. Simpson, A. Blazhev, et al.. The Generalized Centroid Difference method for lifetime mesaurements via $\gamma$-$\gamma$ coincidences using large fast-timing arrays. Fifteenth International Symposium on Capture Gamma-Ray Spectroscopy and Related Topics (CGS15), Aug 2014, Dresden, Germany. pp.01013, ⟨10.1051/epjconf/20159301013⟩. ⟨in2p3-01077155⟩

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