Dear FLUKA experts,
A long time ago, I used FLUKA 4-0.1 version to calculate the photoneutron yields from 197Au(g,x)n, natPb(g,x)n, natSn(g,x)n reactions with Eg=16 MeV using USRYIELD card.
Recently, I have done the same calculations using the latest version of FLUKA 4-2.1
However, the results are quite different, particularly in the low-energy regions. The figure below shows the ratio of two FLUKA versions for the 197Au target at two different angles. For other targets, the discrepancy also was seen for other targets as well.
I checked the FLUKA update log files, and there was an explanation about a change in physics as " Spin and parity of the compound nucleus are now accounted for during the evaporation and Fermi break-up stages."
I really appreciate it if you could confirm such discrepancy is coming from that improvement.