USRYIELD- cant get the 'REG' and 'To REG' tabs working

Dear Experts
I have never used USRYIELD and I am trying to learn how to use it to record the angular divergence of the positrons coming out of a surface. I can do it with usrbdx too but I thought this will be a new thing.
The problem I am having is that FLAIR gui wont show me the REGION options. When I go to the editor mode and edit it, it reverts back. I upgraded the FLAIR to latestversion. Can someone please advice about the mistake I am making?

fast_positron_LINAC.flair (1.9 KB) fast_positron_LINAC.inp (1.6 KB)

Dear Saurabh,

The behavior of Flair is correct. If you select EMERGING, FLUKA will score the yield of particles EMERGING from inelastic hadronic interactions. As far as I know, this scoring is not limited to (a) region(s), thus Flair correctly removes the options of region selection.

You can find more information in the manual:


Dear David
thank you for the reply.