|Program name||Package id||Status||Status date|
|Package ID||Orig. computer||Test computer|
|NEA-1864/07||Linux-based PC,PC Windows||Linux-based PC|
GEF is a computer code for the simulation of the nuclear fission process. The GEF code calculates preneutron 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 mercury to seaborgium in spontaneous fission as well as neutron- and proton-induced fission. Multi-chance fission (fission after emission of neutrons and protons) is included. For neutron-induced fission, the pre-compound emission of neutrons is considered. Output is provided as tables and as parameters of fission observables on an event-by-event basis.
The full GEF version includes the calculation of beta-delayed processes, like emission of delayed neutrons and cumulative yields. In addition, it produces tables of fission yields (independent and cumulative yields) in ENDF-6 format.
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 [4,5,6,7,11] 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 from mass tables with gamma competition included.
Model uncertainties, covariances and correlation coefficients are determined by a series of calculations with perturbed parameters. Covariances and correlations of fission yields from two different systems are available.
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
General description of fission observables, K.-H. Schmidt, B. Jurado, Ch. Amouroux, JEFFReport 24, NEA of OECD, 2014
Revealing hidden regularities with a general approach to fission, K.-H. Schmidt, B. Jurado, Eur. Phys. J. A 51 (2015) 176
Influence of complete energy sorting on the characteristics of the odd-even effect in fission-fragment element distributions, B. Jurado, K.-H. Schmidt, J. Phys. G: Nucl. Part. Phys. 42 (2015) 055101
General description of fission observables: GEF model code, K.-H. Schmidt, B. Jurado, C. Amouroux, C. Schmitt, Nucl. Data Sheets 131 (2016) 107
|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 between saddle and scission, 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 multichance 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.