description of fission observables. Released October 18, 2017.
Modification October 23, 2017. (New set of model parameters. Note that this affects the results of the model!)
Modification October 30, 2017. (Spurious structure in pre-neutron yields at exact symmetry removed.)
Modification November 1, 2017. (New set of model parameters. Note that this affects the results of the model!)
Modification November 23, 2017. (Modified parameters for Z=38 shell. Affects the results for light systems!)
Modification November 24, 2017. (Sequence of energy values are now also
allowed for input from file with options "GS" and "EB"; no change in
the physics of the model.)
Modification November 27 - December 20, 2017. (Calculation of fission
probabilities modified - new algorithm. Affects results of multi-chance fission.)
Modification Januray 20, 2018. (Optional scaling of variation of perturbed parameters introduced. Results of GEF are unchanged.)
Modification January 29, 2018. (Calculation of covariances/correlations
between two different systems corrected. Results of GEF are unchanged.)
Modification January 30, 2018. (Model parameters slightly modified, better adjusted to independent yields of 235U(nth,f).)
Short characterisation of GEF 2017/1.2:
The November-23 version of GEF 2017/1.2 is the result of a careful
re-adjustment of the model
parameters, still with special care on the reproduction of the fission
observables of 235U(nth,f) and a tentative description of systems in
the Hg-Pb region. Because there were many substantial modifications
with respect to GEF 2016/1.2, we are still checking "all corners" of
the code. Therefore this GEF version should still be considered as
"under development". When the new features are not needed, GEF 2016/1.2 may also be used as a stable alternative.
Properties of GEF 2017/1.2: GEF
2017/1.2 is the result of a new careful and comprehensive fit of the
experimental data. In particular, the mass distribution of 235U(nth,f),
the system for which the most accurate data exist, was considered with
special care. GEF 2017/1.2 replaces the preliminary version GEF
2017/1.1 that was the first which achieved an appreciably improved
description of the mass-yield data for 235U(nth,f) by the replacement
of the yield for A=129 by an alternative experiment (see figure below).
Less weight has been layed on a good description of spontaneous
fission. In particular, the far-reaching tails of the super-asymmetric
fission channel are underestimated by this version of the GEF model,
because we could not find a consistent description that also reproduces
the data of neutron-induced fission.
GEF 2017/1.2 provides also a tentative description of the
mass yields in the mercury-lead region, e.g. the beta-delayed fission
of 180Hg, the proton-induced fission of 201Tl and other systems in this
region. In addition, the excitation-energy-dependent influence of shell
effects on the symmetric fission channel has been reconsidered, leading
to modifications of the TKE and of the mass-dependent prompt-neutron
Also the influence of pairing on the fission probabilties near the threshold has been re-considered.
Finally, an error in the calculation of the fission probability that
appeared for nuclei with a strong ground-state shell effect has been
corrected. This error appears in all previous GEF versions.
The mass distribution of 235U(nth,f) from GEF-2017/1.2 (red
comparison with the ENDF/B-VII evalution (black symbols with error
bars). The calculated contributions from different
fission channels are traced in green. 10 million events have been
calculated. The data point for A=129 is taken from H. Thierens, D. de
Frenne, E. Jacobs, A. de Clercq, P. D'Hondt, A.J. Deruytter
Instrum. 134 (1976) 299-308.
An extended version of GEF-2017/1.2
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 runs also on OS X (e)
with Wine (d).
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
Complete package, revised
(In March 2019 it was realized that the transision from asymmetric to symmetric fission in Fm isotopes is not well
reproduced by the original GEF 2017/1.2 version This package offers a revised version.)
(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