Application of Calorimetric Low-Temperature Detectors for the Investigation of Z-Yield Distributions of Fission Fragments

¹ GSI Helmholtzzentrum für Schwerionenforschung GmbH, 64291 Darmstadt, Germany
² Institut für Physik der Universität Mainz, 55128 Mainz, Germany
³ Institut Laue-Langevin, 38042 Grenoble Cedex 9, France
⁴ Institut für Atom- und Molekülphysik, Justus-Liebig-Universität, 35392 Giessen, Germany
⁵ Physik-Department, Technische Universität München, 85748 Garching, Germany
⁶ Physikalisches Institut, Eberhard Karl Universität, 72076 Tübingen, Germany

^* Corresponding author: s.dubey@gsi.de

Published online: 14 November 2018

Abstract

In recent experiments, the new concept of calorimetric low-temperature detectors (CLTDs) was applied for the first time for the investigation of isotopic yields of fission fragments. Fragments from neutron-induced fission sources were mass-separated by the LOHENGRIN spectrometer at the ILL Grenoble and, after passing silicon nitride membranes used as degraders, detected in a CLTD array. The new detector concept of a thermal detector provides a fundamental advantage over conventional ionization-mediated detectors, in particular for heavier particle masses at low energies. Using fissile targets of ²³⁵U, ²³⁹Pu and ²⁴¹Pu, nuclear-charge separation was studied in the mass region 82 ≤ A ≤ 139. For light fragments, the Z resolution matches historically best values with conventional techniques, while for heavier masses substantial improvement was attained. We have gained first LOHENGRIN data on the isotopic yields in the light-mass group of ²⁴¹Pu. Towards mass-symmetry, known Z-yield data were supplemented in the range A = 110 to 113 for ²⁴¹Pu and ²³⁹Pu. Extended data sets were cumulated for A = 92 and 96 due to a recent request from studies on the reactor anti-neutrino spectrum. Furthermore, considerable progress was achieved to extend isotopic yield measurements up to the heavy-mass region, hardly accessible until now.