Abort called from DEDX reason Exceeded upper dp/dx abscissa

Dear FLUKA experts,

I was using isotope card, and while using Am - 241, I got an error message saying :
Abort called from DEDX reason Exceeded upper dp/dx abscissa. Run stopped!
STOP Exceeded upper dp/dx abscissa.

From the previous discussion threads, I could see that this issue can be caused if the energy value in beam card is less than the sampled energy. I have used 5 MeV, even 1 GeV, still I got the error. If I change this isotope to cobalt, no error is there. Can you please guide me? Is this because alphas have very small range in air ?

Here are the test files:

test.inp (1.2 KB)
source.f (9.1 KB)


Dear Riya,

This problem was reported several months ago in this thread and was duly fixed for FLUKA version 4-2.1, released Dec 14, 2021, as per the corresponding RELEASE-NOTES.

You must be running an older version. I warmly recommend to stay regularly updated with the latest released version.

With kind regards,



Dear @cesc

Yes, it is now working. Thank you.