Gamma and conversion electron spectroscopy using GABRIELA
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Special Article - New Tools and Techniques
Gamma and conversion electron spectroscopy using GABRIELA R. Chakma1,a , K. Hauschild1, A. Lopez-Martens1, A. V. Yeremin2 , O. N. Malyshev2 , A. G. Popeko2 , Yu. A. Popov2 , A. I. Svirikhin2 , V. I Chepigin2 , O. Dorvaux3 , B. Gall3 , K. Kessaci3 1
Université Paris-Saclay, CNRS/IN2P3, IJCLab, 91405 Orsay, France Flerov Laboratory of Nuclear Reactions, JINR, 141980 Dubna, Russia 3 CNRS, IPHC UMR 7178, Université de Strasbourg, 67000 Strasbourg, France
2
Received: 11 June 2020 / Accepted: 1 September 2020 / Published online: 1 October 2020 © Società Italiana di Fisica and Springer-Verlag GmbH Germany, part of Springer Nature 2020
Abstract GABRIELA (Gamma Alpha Beta Recoil Investigations with the Electromagnetic Analyzer) is a detection system installed at the focal plane of the SHELS (Separator for Heavy Elements Spectroscopy) recoil separator for gamma and internal conversion electron spectroscopy of heavy and superheavy nuclei. GABRIELA has recently been upgraded. The characteristics of the new setup are presented using the Geant4 Monte Carlo simulation toolkit and validated against experimental results. The impact of summing on the gamma-ray and electron detection efficiencies is discussed.
1 Introduction Superheavy nuclei are unique nuclear systems under large Coulomb forces owing their existence to strong quantum shell effects. The quest for the next proton and neutron spherical shell closures motivated the idea of ‘the island of stability’, where residing nuclides are predicted to have half-lives that vary over tens of orders of magnitude, possibly spanning the age of the earth [1]. Although there is a consensus across different theoretical models in the prediction of the next neutron shell closure at N = 184, the position of the next proton shell closure at either Z = 114, 120, or 126 remains controversial [2]. Despite evidence in the measured lifetimes of the heaviest nuclei synthesized (see the review [3]), the anticipated island of stability awaits discovery. With the current state of technology, the lighter transfermium nuclei are relatively easier to synthesize as compared to their heavier counterparts. To reduce large extrapolations of the nuclear models to the island of stability, the study of the nature, sequence, and spacing of the states of the lighter heavy nuclei are pertinent. Hitherto the spectroscopic data in the transfermium region remain sparse (see fig. 1 of ref. a e-mail:
[email protected] (corresponding author)
[4]). Constant efforts are underway in major experimental facilities around the globe. Recent developments in nuclear spectroscopy techniques and instrumentation have allowed the identification of single-particle and collective states in many heavy systems. To study the structure in detail, two techniques are currently employed: the first one is prompt spectroscopy at the target [4], generally performed using the recoil decay tagging method (RDT) [5,6]. The other complementary technique is decay spectroscopy either at the
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