Dear Honghu,
currently Flair only can visualize the beam direction set on the BEAMPOS card, but an user routine obviously overwrites this.
The effectiveness of showing particle track - especially when divergence sampling is used - is limited.
But there are two options you can consider to visualize your source:
-
Simply use a fine enough USRBIN scoring around the beam position. If you are curious about the energy distribution sampled in your source routine. You can place a sphere around the source and use an USRBDX scoring.
-
Use the USERDUMP card with at least scoring the Source with Complete selected, then plotting the available values (coordinates, directions of the primaries) in Flair.
For more detail, please have a look at:
https://flukafiles.web.cern.ch/flukafiles/manual/USERDUMP.html
https://flair.web.cern.ch/flair/manual/Userdump.html
Cheers,
David