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GEF 2018/1.1

General description of fission observables. Released June 21, 2018.

Short characterisation of GEF 2018/1.1: The model parameters were re-adjusted on the basis of recent empirical fission-fragment mass distributions and independent yields. A rather good agreement with the mass yields from the JEFF 3.3 evaluation was achieved, in particular for 235U(nth,f) (see figure). Isomeric ratios are calculated with the spectroscopic data from NUBASE 2016. Some corrections, improvements and new features were inserted (see the protocol at the beginning of GEF.bas).

Properties of GEF 2018/1.1: According to rather extensive tests, GEF 2018/1.1 gives a good description of different kind of fission data for a large variety of systems. Some problems of GEF 2017/1.2 could be solved, e.g. there are no inconsistencies in the description of thermal-neutron-induced and spontaneous fission any more.

22 Dec. 2018: Estimated nuclear properties included in NucpropNUBASE.bas.
                          Problem in GUI for Windows version corrected.
27 Jan. 2019: Several technical changes. The physics should be unchanged.
07 Feb. 2019: Technical problems in list-mode output (Linux and Windows versions) corrected.

Mass distribution of U235T

The mass distribution of 235U(nth,f) from GEF-2018/1.1 (red points) in comparison with the JEFF 3.3 evalution (black symbols with error bars). The calculated contributions from different fission channels are traced in green. 10 million events have been calculated.

See also this gallery, where the mass distributions of other systems from different evaluations and experiments are compared with the results of the GEF code.

An extended version of GEF-2018/1.1 that includes delayed processes (output of delayed-neutron multiplicities, delayed-neutron emitters, cumulative fission-fragment yields in ENDF format) is available on demand.
It provides also an option for producing random files of fission-fragment yields in ENDF format.

We are happy about any feed-back (mail to schmidt-erzhausen<at>t_online.de). This helps to correct errors, to improve the quality of the model and to better respond to the needs and preferences of the users.

Use of the GEF code is subject to the GNU GENERAL PUBLIC LICENSE agreement that you find here: <License>.

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).  The Windows version runs also on OS X (e) with Wine (d).

a) FreeBASIC is available from http://www.freebasic.net/ with no cost.
b) Windows is either a registered trademark or a trademark of Microsoft Corporation in the United States and/or other countries.
c) JustBasic is available from http://www.justbasic.com/ with no cost.
d) Wine is a windows compatibility layer for Linux and Mac OS X (http://www.winehq.org/).
e) OS X is a trademark of Apple Inc., registered in the U.S. and other countries.

Quick start on Windows:

Quick start on Linux:

Windows version

Input mask of the graphical user interface:

Input maks of GEF GUI

For Windows and Linux

Complete package


Readme file (Technical information, list of relevant publications)
JEFF-Report 24, part I (Comprehensive documentation of the GEF model.)
JEFF-Report 24, part II (Technical information on the GEF code.)

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)   (short sample of most complete event list)
Raw data for the multi-variate 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 complete distributions of a number of fission observables before emission of prompt neutrons and prompt gamma radiation with the GEF model.


Technical description of the subroutine

FreeBASIC version

In preparation

FORTRAN version

In preparation