Low energy neutron cross section for 54Fe

Dear FLUKA users,
As we know, the low energy neutron cross section can be added by the LOW-MAT card together with the MATERIAL card, in the manual as shown below, I guess only 56Fe can be linked with the cross section. Now the material in my simulation contains the 54Fe, so how can I link the cross section data? Any suggestions are appreciated.

Your guess is not correct, since the IRON cross sections made available in the low energy neutron library refer to the iron natural isotopic composition, including the 54Fe percentage. Conversely, they are not available for single iron isotopes.
By the way, if in the MATERIAL card you call your material IRON, the aforementioned cross sections (namely the ones corresponding to the first IRON entry above, applying to room temperature) will be automatically used, with no need for a LOW-MAT card.
If your iron material does not reflect the natural isotopic composition, you will not be able to use low energy neutron cross sections other than the ones assuming the latter, though.

Thanks a lot. :grinning: