I am seeking guidance on two issues related to my simulation setup:
I would like to score the one-way current using the USRBDX card. However, I understand that USRBDX is limited to scoring particles between two adjacent regions. In my case, I need to score the particles reaching each of four detectors placed around the target. Could you please suggest an alternative method that would allow me to achieve this?
My second concern is regarding simulations involving multiple beam positions. I initially used the built-in loop option in Flair, but it consumes a large amount of memory and causes the system to hang, requiring a full restart. Since I cannot run all beam positions in a single execution due to memory constraints, is there a more memory-efficient way to loop through all defined positions and still retrieve the results, either combined or individually for each run?
Regarding your first question, you are correct that USRBDX scores the one-way particle current between two adjacent regions. To score the particles reaching your detectors, you can still use USRBDX by defining Region 1 as AIR and Region 2 as detecto1/2/3/4. This way, you can define four USRBDX cards, one for each detector allowing you to record the particle current entering each detector.
In your input file I have noted that you don’t indicate a surface area. This is fine, as long as you include the factor in the post-processing. You can find more information on that topic in the Scoring II lecture of this years FLUKA beginner course.
For your second question about handling multiple beam positions:
If you only have a few distinct positions, you can use #DEFINE cards in your input file to specify different beam positions and then run the simulations sequentially, selecting the desired beam position before each run. This allows you to analyse the results for each beam position separately.
Alternatively, you may consider using the SPECSOUR in combination with SPOTBEAM as described in the Sources and Preprocessor lecture of this year FLUKA beginner course. This allows the definition of several beam spots within a single run.
If you have large number of positions, a better approach is to use a custom source routine (more information in the Source Routine lecture), where the beam position is sampled from a list or distribution at runtime, avoiding the loops in FLAIR.
Please let me know if any part of this is unclear.