G4NDL "Elastic/FS" files

In am using the G4NDL library for high precision neutron cross sections at low energy. I would like to know what the files in this directory specify:


I looked in the physics manual and it seems the only possible reference is under the “Final State” section where the manual talks about the “final state files:”

Unlike the format of the cross section files, the format of the final state files is not straightforward and pretty com-plicated. Even though each of these files follows the same format rules, the actual length and appearance of each filewill depend on the specific data. The format rules of the final state files are a subset of the ENDF-6 format and a deepunderstanding of the format is required to correctly interpret the content of the files. Because of limited resources, wedo not plan to provide a complete documentation on this part in the near future.

Are the files in /Elastic/FS “final state files” and what does that mean? What part of the data evaluations (ENDF, JENDL, etc) does this information come from?

Are the files for a similar purpose to the files in /Fission/FS or /Inelastic/F13 for example?

Dear villaa,

“Final state” refers to all the information needed to create the secondary particles, after the nuclear reaction takes place. In practice, all the data but cross sections.

The files in G4NDL4.5/Elastic/FS/ will contain info concerning the angular distribution of the neutron after the elastic reaction. Which is all the information the code needs in this case. It corresponds to MT=2, MF=4 data, in ENDF-6 format (I don’t know if it could be also MF=6 in this case).

The files in Fission/FS and Inelastic/F13 contain information needed to generate the secondary particles in fission and “F13” inelastic reactions (I don’t know which channel is “F13”, but coud be (n,2n), (n,np) … any no-elastic, no-fission and no-capture channel). The data there will be particle yields, and energy and angular distributions: MF=4,5,6,12,13,14 and 15.



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yes, it is final state data.


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I found that in older documentations there is a section called “Further Information,” that contains a link to a description of the “Final State” files. For example in the 10.3 documentation.


Newer versions of the documentation do not render the link correctly, so it can’t be read. The link to the documentation is:


The documentation is not easy to read or understand.