GEF 2014/1.2

General description of fission observables. Released January 25, 2014.
(Modified description of multi-chance fission.
Prompt-neutron spectrum slightly shifted in energy after correction of binning problem.)
(Some technical corrections applied on February 1, 2014, without changing the physics of the model.)


Stand-alone version (Monte-Carlo method)

The stand-alone version of the GEF code is written in FreeBASIC (a). The FreeBASIC compiler produces binary code from the same source on Windows (b) and on Linux. The executable uses the C library.  For  the Windows version, a GUI is provided, written in JustBasic (c). The Windows version runs also on Linux with Wine (d).

Quick start on Windows:

Quick start on Linux:

Sample output plot:

Mass distribution of 239Pu(nth,f)

Calculated prompt-neutron spectra (red) compared with experimental data (black):

Spectra for 235U(nth,f) and 252Cf(sf)

Windows version


Input mask of the graphical user interface:

GUI for windows

Linux version


For Windows and Linux

Complete package


Readme file (Technical information, list of relevant publications)
EFNUDAT report (First comprehensive documentation)
Report JEFDOC 1423 (Updated documentation)

Source (for Windows and Linux)

Source files


Input files for extended input options
Distribution of entrance energies (example)
List of input parameters (example)
See Readme file for more detailed information.
Data tables in XML format (example)
List-mode file (example)
Raw data for the multi-variant distribution of fission-fragment yields from calculations with perturbed parameters (example)
See Readme file for more detailed information.

You may consider using the Windows version of GEF on Linux with Wine in order to profit from the more comfortable input handling offered by the graphical user interface. This option may also solve problems of missing libraries under Linux.

Subroutine (Folding method)

The subroutine aims for being used in combination with other nuclear-reaction codes. For a given fissioning nucleus with excitation energy E* and angular momentum I it calculates a number of fission observables with the GEF model.

Complete package


Technical description of the subroutine

FreeBASIC version


FORTRAN version


(a) FreeBASIC is a free compiler (
(b) Windows is either a registered trademark or a trademark of Microsoft Corporation in the United States and/or other countries.
(c) JustBasic is a free interpreter (
(d) Wine is a windows compatibility layer for Linux (