Stop invalid whydr

Dear FLUKA experts,

We are carrying out a FLUKA simulation to determine the pion decay photon spectrum expected from energetic ions impacting a thick target source with solar atmosphere composition. A beam of protons is directed at a cuboid composed of a substance which is mostly hydrogen, with small quantities of helium, carbon, oxygen, nitrogen, etc. The simulations run fine and produce understandable results for moderate proton energies, up to a few GeV, but if we go to 10 GeV we start to find an event that causes a crash with the error message

Abort called from STCPPR reason INVALID WHYDR Run stopped!

If we run the simulation with a single species target source there is no error. So, we guess this is something to do with transport in our composite medium. We can work around it by doing several runs with modest numbers of primaries. Not all of them will crash and we can use results from the successful ones in the usual way. But this is slow and fiddly, and we would like to understand what causes the error in case it highlights something we should be aware of in our results.

Example .flair, .inp and .err files are attached. Thanks in advance for help.

test_01001.err (11.7 KB)
test.flair (2.5 KB)
test.inp (2.4 KB)

1 Like

Dear Sergio,

Thanks for reporting this crash, which was due to a failed evaluation of the capture probability for an antiproton on 4He.

This issue has now been fixed and will be included in an upcoming minor release, ideally before the end of the year.

With kind regards,



Dear Francesc,

Thank you very much for the prompt response and the fix!

Best regards,