Optical photons during geometry transformation

Dear Fluka experts, I’ve faced with a problem dedicated to optical photons detection. The geometry of the experiments is quite simple: the model that consists of several layers of various materials is irradiated by monoenergetic electrons. As a result of electron interaction with media, the model generates optical photons (within EJ212A layer). Then these optical photons are absorbed inside FIBERS region, where in turn new optical photons are generated (with different wavelength). These new photons travel within media until they reach DI region where they are absorbed. In its first iteration, the model works just fine. But when I’m trying to make some geometrical transformations by using ROT-DEFI card and $start_transform directives, the model stops working. The model still generates optical photons and everything works as it should be until photons reach GL region. In this region they just disappear without any reason. Could you please help me to find out the reason of such behavior? I attached the input files to this message (det_v1 is a model without geometry transformation, det_v2 is a model with geometry transformation)

abscff.f (1.5 KB)
det_v1.inp (9.0 KB)
det_v2.inp (9.5 KB)
wvlnsh.f (2.7 KB)

Dear @Alexy ,

Carefully looking at the model with transform, I noticed some errors in the geometry. It could be the cause of your problem. In flair, there should be no red boundaries or ‘x’. Please fix them and see if that solves the problem.

Dear Benoit,

Thank you for your reply, but I’m afraid that the problem is different. I’ve noticed that the problem you mentioned appear in Flair, because it does not implement transformations automatically when one opens a file. If you click on start_transform card and redefine Trans: value for every transformation card the error will disappear. But even in this case the optical photons won’t reach the detector.

Dear @Alexy ,

Indeed, I also managed to see the transform, but after reopening flair.

As for your problem, I suggest the following solution: You should identify your transformations with a name that cannot be interpreted as a number in the ROT-DEFI card. In your case, you used 111 and 112 which you could replace with, for example, TRANS1 and TRANS2. Flair did not mind this detail and shows you the correct transformation. However, FLUKA will almost surely not behave like you intend at runtime.

The problem is when you call the transformation using the $start_transform statement. There, you must provide the name of the transformation. If the name you provide can be interpreted as a number, FLUKA will switch to number-based input and look up the transform associated with that number. In your case you meant to create a transform “111” (string) but FLUKA looked up the transform 111 (integer).

If you wish to use number-based input with ROT-DEFI, you must use the ID field and ignore the Name field. Please note that this approach only works with a pure FLUKA input file, not in Flair.

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Dear Benoit,

Thank you very much. I followed your advice about changing of ‘111’ into ‘TR1’ and it worked.