Abstract
We present a direct method to measure fission product yield distributions (FPY) and isomeric yield ratios (IYR) for spontaneous fission (SF) fragments. These physical properties are of utmost importance to the understanding of basic nuclear physics, the astrophysical rapid neutron capture process ('r process') of nucleosynthesis, neutron star composition, and nuclear reactor safety. With this method, fission fragments are produced by spontaneous fission from a source that is mounted in a cryogenic stopping cell (CSC), thermalized and stopped within it, and then extracted and transported to a multiple-reflection time-of-flight mass-spectrometer (MR-TOF-MS). We will implement the method at the FRS Ion Catcher (FRS-IC) at GSI (Germany), whose MR-TOF-MS relative mass accuracy (~ 10-7) and resolving power (~ 600,000 FWHM) are sufficient to separate all isobars and numerous isomers in the fission fragment realm. The system's essential element independence and its fast simultaneous mass measurement provide a new direct way to measure isotopic FPY distributions, which is complementary to existing methods. It will enable nuclide FPY measurements in the high fission peak, which is hardly accessible by current techniques. The extraction time of the CSC, tens of milliseconds, enables a direct measurement of independent fission yields, and a first study of the temporal dependence of FPY distributions in this duration range. The ability to resolve isomers will further enable direct extraction of numerous IYRs while performing the FPY measurements. The method has been recently demonstrated at the FRS-ICr for SF with a 37 kBq 252Cf fission source, where about 70 different fission fragments have been identified and counted. In the near future, it will be used for systematic studies of SF with a higher-activity 252Cf source and a 248Cm source. The method can be implemented also for neutron induced fission at appropriate facilities.
Highlights
Nuclear fission was discovered in 1939, and has since been extensively researched and applied to the design and construction of nuclear reactors
Fission Product Yields (FPYs) and Isomer Yield Ratios (IYRs) form an integral part of the prediction of antineutrino spectra generated by nuclear reactors
The method is realized at the FRS Ion Catcher (FRS-IC) [15], at the FRagment Separator (FRS) [16] in GSI (Germany)
Summary
Nuclear fission was discovered in 1939, and has since been extensively researched and applied to the design and construction of nuclear reactors. Experimental data on the high fission peak is limited to ‘cold fission’ (i.e. without neutron emission) [12], and to an evaluation based on the measurement of two nuclides per isobar chain [13]. IYR data for 252Cf SF exist for only ∼10 nuclides, in a limited region (A = 128-138) in the high fission peak [14]. It was extracted from γ-ray spectroscopy coupled with radiochemistry, relied on γ-ray branching ratios that were not always well-known, and was limited to fragments with half-lives longer than one minute
Sign-in/Register to view highlights & summary Sign-in/Register to access full text options 
Talk to us
Join us for a 30 min session where you can share your feedback and ask us any queries you have
Schedule a callDisclaimer: All third-party content on this website/platform is and will remain the property of their respective owners and is provided on "as is" basis without any warranties, express or implied. Use of third-party content does not indicate any affiliation, sponsorship with or endorsement by them. Any references to third-party content is to identify the corresponding services and shall be considered fair use under The CopyrightLaw.
