|Program name||Package id||Status||Status date|
|Package ID||Orig. computer||Test computer|
|NEA-1864/06||Linux-based PC,PC Windows|
GEF is a computer code for the simulation of the nuclear fission process. The GEF code calculates pre-neutron and post-neutron fission-fragment nuclide yields, angular-momentum distributions, isomeric yields, prompt-neutron yields and prompt-neutron spectra, prompt-gamma spectra, and several other quantities for a wide range of fissioning nuclei from polonium to seaborgium in spontaneous fission and neutron-induced fission. Multi-chance fission (fissionafter emission of neutrons) is included. For neutron-induced fission, thepre-compound emission of neutrons is considered. Output is provided as tables and as parameters of fission observables on an event-by-event basis.
Specific features of the GEF code:
The mass division and the charge polarisation 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  governs the interplay of macroscopic and microscopic effects.
Five 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 .
The stiffness of the macroscopic potential with respect to mass asymmetry is deduced from the widths of measured mass distributions .
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 from the fragments is calculated with a Monte-Carlo statistical code using level densities from empirical systematics  and binding energies with theoretical shell effects with gamma competition included.
Model uncertainties and covariances are determined by a series of calculations with perturbed parameters.
Multi-chance fission is supported.
Pre-compound emission of neutrons is considered for neutron-induced fission.
The main routines are written in FreeBASIC (http://www.freebasic.net/). FeeBASIC produces compiled binary code using the C run-time library. Graphics output is based on the X11 library. A graphical user interface is provided for Windows, written in JustBasic (http://www.justbasic.com/), which has a specific run-time library. The Windows version of GEF runs also under WINE on LINUX.
|Package ID||Status date||Status|
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
Nuclear-fission studies with relativistic secondary beams: analysis of fission channels, C. Boeckstiegel et al., Nucl. Phys. A 802 (2008) 12
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
Entropy-driven excitation-energy sorting in superfluid fission dynamics, K.-H. Schmidt, B. Jurado, Phys. Rev. Lett. 104 (2010) 212501
New insight into superfluid nuclear dynamics from the even-odd effect in fission, K.-H. Schmidt, B. Jurado, arXiv:1007.0741v1 [nucl-th]
Thermodynamics of nuclei in thermal contact, K.-H. Schmidt, B. Jurado, Phys. Rev. C 82 (2011) 014607
Final excitation energy of fission fragments, K.-H. Schmidt, B. Jurado, Phys. Rev. C 83 (2011) 061601(R)
Inconsistencies in the description of pairing effects in nuclear level densities, K.-H. Schmidt, B. Jurado, Phys. Rev. C 86 (2012) 044322
|Package ID||Computer language|
Multi-chance fission is supported, except when a distribution of excitation energies at fission is provided on input. The results on neutron emission prior to fission and prompt-neutron emission from the fragments are given separately.
The sequence of the events in the list-mode output is sorted by energy at fission in the case of multi-chance fission in order to save computing time.
An optional enhancement factor may be specified. A value >1 increases the statistics of the Monte-Carlo calculation and hence reduces the statistical uncertainties of the results. Default value is 1.E5 events. With this value, the statistical uncertainties are already smaller than the model uncertainties in most cases. Higher statistics may be useful to compare different systems, to study systematic trends and to determine reliable covariances.
GEF provides all results event by event in a list-mode file on demand.
Keywords: Monte Carlo method, nuclear fission, statistical models.