Dear @dbozzato
Here I provide the Flair file
Spec.flair (2.1 KB)
Please note that I did not use source.f routine but I followed instructions in Sampling from energy spectra so that I could use the spectrum data.
After extracting data, I rearranged the energy values into energy bins as used in the ASCII file. The values in the last column are the intensities corresponding to the intensity values on the spectrum in the reference article. They were fed to the ASCII file without changes.
In FLUKA, I used the USRBDX card to score the neutron spectrum in linear energy of neutrons escaping the spherical region surrounding the source. In Flair, I chose Y to get a linear spectrum instead of a logarithmic one.