Lethargy for neutron

dear fluka user,
by using USRBDX, (for lethargy calculation), i cant get plot dphi/d(lnE) in surface at top of geometery.
if we want to calculate the lethagy on th outer surface of a for example cube, toward the sky, which region should be specify in USRBDX?
what’s the problem?or which option in USRBDX card is wrong?
test.flair (8.1 KB)
test.inp (12.8 KB)
best regards

dear Francesco,
according to your recent activities in USRBDX field,The LOW-PWXS was added to my input, but i get no plot.

lethargy in *tab.lis file is zero… why???

You did not indicate the second region defining the scoring boundary (so the region #2, VOID, is taken by default, and it does not share any boundary with ROOF6).

thanks for your help.
I applied your reply… but the output is zero.

does more nps can solve this problem?

dear Francesco
The problem solved…
i change the “opt:” in biasing card…
and run again.
Thank you for your guidance.
the best wishes,