While using the GCR-ALLF card, the manual explained that WHAT(2) means height of the (infinitely large surface) source when set to negative values, and means radius when set to positive. The explanation is not so clear and raises a few concerns.
1.Is the height WHAT(2) or the absolute value of WHAT(2)? (for example if WHAT(2) is -50.0, is the height -50cm or 50cm)
2.By default, does the source generate particles in one direction or both directions? If in one, is it up or down? Does it shoot all particles in the same direction or evenly spread over solid angle?
3.Is it possible to set the source in the other half of the world (cuz if surface source is only when WHAT(2) <0 it naturally could only be in one half of the geometry)? And is it possible to set the source surface in a direction other than the default xy-plane?
Idk but my estimators are giving out zero outputs so there’s gotta be something wrong with my comprehension of the manual. Thx.
Input files
Please upload all relevant files. (FLUKA input file, Flair project file, user routines, and data files)
sorry for the long delay. From what I have gathered:
the negative is only used for choosing the type of source. In your example, setting WHAT(2) is -50.0, creates a plane which emits particles
they generate particles on one side, but not one direction; that means, e.g. the plane you defined above will emit particles downwards, but not always perpendicular to the plane. Same with the sphere, inward, but not always perpendicular.
I believe the only configurations are the default ones described in point 1 and 2. For other permutations (e.g. plane in y-z plane, direction of particles reversed) you will have to write a source routine.
what estimators are you using? Please try placeing USRBDX to see surface crossings.
Thanks for your response, it helps.
However when setting USRBDX at z=0 and using the mentioned source, there are only protons going from z<0 to z>0(probably from interaction with material), and none going from z>0 to z<0. Thus I believe that the source is z=-50.0cm emitting particles downwards.
By the way, in some cases the source height is irrelevant (all you need is evenly distributed half-space emission), cleverly setting the target surface at z=-100.0cm or any z smaller than |WHAT(2)| would produce correct results regardless of the ambiguity. Which is what I did for safety, and it indeed works.
very good point, thank you for following up. Can you please send me your input file so I can make sure for your specific cases everything applies?
From my own testing, I can confirm that with what(2) = -|z|, the source is set as a beam of particles with origin at BEAMPOS (0,0,0 by default) coordinates and directed downwards, with cosine weighted distribution of angles.
This differs from my answer above, based on the description provided in the documentation. Apologies for the confusion.
A fix will be devised soon. Until then, please use a custom source routine to achieve the desired result, or a very large sphere with appropriate shift in geometry.
let me know if you managed to solve this issue with the user routine, and if you can send me your input. I have written a source.f routine that you may use to simulate the expected behavior of GCR-ALLF.
As described in the above replies I used a trick of shifting the target downwards to solve the problem, rather than actually confronting it with the user routine. It was unnecessary to grind on this for me so I just moved on.
My input has been drastically changed since this conversation and no longer relevant, since I changed to spherical geometry later on. However I do have a copy of my simple input some one month ago or something. Hope it helps.