EPJ Web of Conferences
Volume 93, 2015CGS15 – Capture Gamma-Ray Spectroscopy and Related Topics
|Number of page(s)||6|
|Published online||28 May 2015|
The Generalized Centroid Difference method for lifetime measurements via γ-γ coincidences using large fast-timing arrays
1 IKP der Universität zu Köln, Zülpicher Str. 77, 50937 Köln, Germany
2 Grupo de Fisica Nuclear, FAMN, Universidad Complutense, CEI Moncloa, 28040 Madrid, Spain
3 National Centre for Nuclear Research, BP1, ul. Hoza 69, PL-00-681, Warsaw, Poland
4 LPSC Grenoble, 53, rue des Martyrs, 38026 Grenoble Cedex, France
5 School of Engineering, University of the West of Scotland, Paisley, PA1 2BE, United Kingdom
6 Institut Laue-Langevin, CS 20156, 38042 Grenoble Cedex 9, France
7 GANIL, Bd Henri Becquerel, BP 55027, 14076 Grenoble Cedex 05, France
8 INFN, Sezione di Padova, Via Marzolo 8, 35131 Padova, Italy
9 Faculty of Physics, University of Warsaw, ul., Hoza 69, PL-00-681, Warsaw, Poland
10 SCEM, University of Brighton, Lewes Road, Brighton, BN2 4GJ, United Kingdom
11 IKP der Technische Universität zu Darmstadt, Schlossgartenstr. 9, 64289 Darmstadt, Germany
12 CEA de Saclay, Route Nationale, 91400 Gif-sur-Yvette, France
13 Faculty of Physics, University of Sofia, “St. Kliment Ohridski”, 1164 Sofia, Bulgaria
14 Department of Physics, University of Surrey, Guildford, GU2 7XH, United Kingdom
15 Horia Hulubei NIPNE, 77125 Bucharest, Romania
16 NPL, Teddington, Middlesex, TW11 0LW, United Kingdom
17 IPN de Lyon, 4, Rue Enrico Fermi, 69622 Villeurbanne Cedex, France
a e-mail: firstname.lastname@example.org
Published online: 28 May 2015
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.
© Owned by the authors, published by EDP Sciences, 2015
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