Independent isotopic fission yields of ²⁵²Cf spontaneous fission via mass measurements at the FRS Ion Catcher

¹ Israel Atomic Energy Commission, P.O. Box 7061, Tel Aviv 61070, Israel
² II. Physikalisches Institut, Justus-Liebig-Universität Gießen, 35392 Gießen, Germany
³ Extreme Light Infrastructure-Nuclear Physics (ELI-NP), Horia Hulubei National Institute for R&D in Physics and Nuclear Engineering, Str. Reactorului 30, 077125 Bucharest-Măgurele, Romania
⁴ Doctoral School in Engineering and Applications of Lasers and Accelerators, University Polytechnica of Bucharest, 060811 Bucharest, Romania
⁵ Soreq Nuclear Research Center, Yavne 81800, Israel
⁶ School of Physics and Astronomy, Tel Aviv University, Tel Aviv 6997801, Israel
⁷ GSI Helmholtzzentrum für Schwerionenforschung GmbH, 64291 Darmstadt, Germany
⁸ Department of Physics, Nuclear Research Center Negev, P.O. Box 9001, Beer Sheva 84190, Israel
⁹ Jozef Stefan Institute, SI-1000 Ljubljana, Slovenia
¹⁰ Nuclear Energy Group, ESRIG, University of Groningen, 9747 AA Groningen, The Netherlands
¹¹ Department of Physics and Astronomy, Uppsala University, SE-75105 Uppsala, Sweden
¹² Helmholtz Forschungsakademie Hessen für FAIR (HFHF), GSI Helmholtzzentrum für Schwerionenforschung, Campus Gießen, 35392 Gießen, Germany
¹³ Johannes Gutenberg-Universität Mainz, 55099 Mainz, Germany

^* e-mail: mardor@tauex.tau.ac.il

Published online: 26 May 2023

Abstract

We present first preliminary results of a novel method for measuring independent isotopic fission yields (IIFYs) of spontaneous fission (SF) via direct mass measurements, at the FRS Ion Catcher (FRS-IC) at GSI. Fission products were generated from a ²⁵²Cf source installed in a cryogenic stopping cell, and were identified and counted with the multiple-reflection time-of-flight mass spectrometer (MR-TOF-MS) of the FRS-IC, utilizing well-established measurement and data analysis methods. The MR-TOF-MS resolves isobars unambiguously, even with limited statistics, and its non-scanning nature ensures minimal relative systematic uncertainties amongst fission products. The analysis for extracting IIFYs includes isotope-dependent efficiency corrections for all components of the FRS-IC. In particular, we applied a self-consistent technique that takes into account the element-dependent survival efficiencies in the CSC, due to chemical reactions with the buffer gas. Our IIFY results, which cover several tens of fission products in the less-accessible high-mass peak (Z = 56 to 63) down to fission yields at the level of 10⁻⁵, are generally similar to those of the nuclear database ENDF/B-VII.0. Nevertheless, they reveal some structures that are not observed in the database smooth trends. These are the first results of a planned campaign to investigate IIFY distributions of spontaneous fission at the FRS-IC. Upcoming experiments will extend our results to wider Z and N ranges, lower fission yields, and other spontaneously-fissioning actinides.