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.
The mass distribution of 235U(nth,f) from GEF-2018/1.1 (red
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
See also this gallery,
where the mass distributions of other systems from different
evaluations and experiments are compared with the results of the GEF
An extended version of GEF-2018/1.1
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
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)
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
version, a GUI is provided, written in JustBasic (c). The Windows
version runs also on Linux with Wine (d). The Windows version
should also run on OS X (e)
with Wine (d). (Did somebody try it?)
a) FreeBASIC is available from http://www.freebasic.net/ with no
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
e) OS X is a trademark of Apple Inc., registered in the U.S. and other
Quick start on Windows:
- Download the binaries
(that includes some additional files).
- Start GEF.bat in a
- Fill in the input mask of the graphical user interface and start
- Output is written to file \out\...
Quick start on Linux:
- Download the binaries.
- Make sure that the binary file GEF is executable.
- Enter ./GEF in a command
- Answer the input dialogue.
- Output is written to file
Input mask of the graphical
For Windows and Linux
(Technical information, list of relevant publications)
24, part I
(Comprehensive documentation of the GEF model.)
24, part II
(Technical information on the GEF code.)
Source (for Windows and Linux)
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.
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
Technical description of the subroutine