o GEF GEneral description of Fission observables - Access to the GEF code (new release December 2011) - Documentation - References
o GEFY GEF-based fission-fragment yield library in ENDF format for 376 fissioning nuclei from Z=88 to Z=106 (August 2011) - spontaneous fission - neutron-induced fission of stable and metastable target nuclei (En = thermal to En = 6 MeV)
The GEF code calculates pre-neutron and post-neutron fission-fragment nuclide yields for a wide range of heavy nuclei from polonium to seaborgium and other fragment properties. The development of GEF has been supported by the European Union in the framework of the EFNUDAT project (http://www.efnudat.eu/) and by the OECD Nuclear Energy Agency. A detailed description of the physics of the code is given in this final EFNUDAT report.
Executables of the GEF code for Windows[a] and Linux are available. They are easy to use: Just download the ZIP file, extract the files and run GEF.bat (Windows [a]) or ./GEF (Linux) in a command window on your computer! The file README.txt contains further information.
[a] Windows is either a registered trademark or a trademark of Microsoft Corporation in the United States and/or other countries.
Download (including copyright information and license.): GEF code, Version 2011/3.7, executables and source (October 2011) GEF code, Version 2011/4.4, executables and source (December 2011)
Authors: Beatriz Jurado (jurado.at.cenbg.in2p3.fr) and Karl-Heinz Schmidt (khs-erzhausen at t_online.de).
Here are some results of the GEF code. (Enlarge figure.)
Main ingredients of the model
The mass division and the charge polarization are calculated assuming a statistical population of states in the fission valleys at freeze-out. The freeze-out time considers the influence of fission dynamics and is not the same for the different collective variables.
The separability principle [1] governs the interplay of macroscopic and microscopic effects.
Four fission channels are considered. The strengths of the shells in the fission valleys are identical for all fissioning systems. The mean positions of the heavy fragments in the asymmetric fission channels are essentially constant in atomic number, as suggested by experimental data [2].
The stiffness of the macroscopic potential with respect to mass asymmetry is deduced from the widths of measured mass distributions [3].
The excitation-energy-sorting mechanism [4,5,6,7] determines the prompt neutron yields and the odd-even effect in fission-fragment yields of even-Z and odd-Z systems.
Neutron evaporation is calculated with a Monte-Carlo statistical code using level densities from empirical systematics [8] and binding energies with theoretical shell effects [9] with gamma competition included.
References: [1] Experimental evidence for the separability of compound-nucleus and fragment properties in fission, K.-H. Schmidt, A. Kelic, M. V. Ricciardi, Europh. Lett. 83 (2008) 32001 [2] Nuclear-fission studies with relativistic secondary beams: analysis of fission channels, C. Boeckstiegel et al., Nucl. Phys. A 802 (2008) 12 [3] Shell effects in the symmetric-modal fission of pre-actinide nuclei, S. I. Mulgin, K.-H. Schmidt, A. Grewe, S. V. Zhdanov, Nucl. Phys. A 640 (1998) 375 [4] Entropy-driven excitation-energy sorting in superfluid fission dynamics, K.-H. Schmidt, B. Jurado, Phys. Rev. Lett. 104 (2010) 212501 [5] New insight into superfluid nuclear dynamics from the even-odd effect in fission, K.-H. Schmidt, B. Jurado, arXiv:1007.0741v1 [nucl-th] [6] Thermodynamics of nuclei in thermal contact, K.-H. Schmidt, B. Jurado, Phys. Rev. C 82 (2011) 014607 [7] Final excitation energy of fission fragments, K.-H. Schmidt, B. Jurado, Phys. Rev. C 83 (2011) 061601(R) [8] Systematics of nuclear level density parameters, Till von Egidy, Dorel Bucurescu, Phys. Rev. C 72 (2005) 044311 [9] Nuclear ground state masses and deformations, P. Moeller et al., Atom. Data Nucl. Data Tables 59 (1995) 185
Required input of GEF: Z and A of fissioning nucleus Excitation mode and excitation energy Quantities available on output of GEF: Relative yields of fission channels Element-yield distribution Neutron-yield distribution (pre- and post-neutron) Mass-chain yields (pre- and post-neutron) Prompt-gamma spectrum (new!) Prompt-neutron spectrum (new!) Fragment angular-momentum distributions (for every nuclide) Relative independent isomeric yields Neutron-multiplicity distribution (Many more quantities are internally calculated and may be listed.)
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GEFY 1.1 (August 2011):
Fission-fragment yields for isotopes of Z = 88 to Z = 106 (376 fissioning nuclei). Independent and cumulative yields. Cumulative yields were calculated using the decay data of JEFF 3.1. Nuclides with half lives longer than 1.E6 years were treated as stable.
Here are some results of the GEF code. (
