OPT-PROD scintillation light production doubt

Dear FLUKA experts,
I have a question related to the production of optical photons with the card “OPT-PROD”, with type “SCINTILL”. The number of optical photons produced is inferior to the one I would expect; I’ve attached an example simulation to better explain the problem I have.

The simulation is relative to a 100keV beam inside a scintillator material. The scintillator is big enough to guarantee that all the energy of the beam is deposited inside the material (I’ve checked through a USRBIN scoring card that this is indeed the case, and each beam photon deposits 100keV). For this example purpose, the scintillation light photon energy is set to 2eV, and the fraction of deposited energy that is converted to scintillation light is set to 0.20. Given these settings, I would expect a production of 100000*0.2/2 = 10000 optical photons per beam particle from the scintillation process. Instead, the number of optical photons produced per beam particle is only around 8200, as reported at line 1567 and 1578 of the .out file attached.

I’d appreciate if you could help me understand this discrepancy, and if there is a different way I could set up the simulation to fix it.

Thank you in advance,
Best regards,

GADOX_optiphoton_test.flair (1.8 KB)
GADOX_optiphoton_test.inp (1.6 KB)
GADOX_optiphoton_test001.out (82.0 KB)

Dear Fabien,

I have performed several tests and this discrepancy always seems to be there. I will try to investigate with other FLUKA experts and let you know once we find where the problem is.

Kind regards

Dear Vojtěch,
first of all thank you for helping me investigate this discrepancy.
I would like to run some simulaitons with scintillators and I was wondering if there were any updates on this matter. Thanks again,
Best regards

Dear @Fabien.Bellini ,
From my experience, I found some of the photons trapped in the scintillators.
Best regards

Dear Fabien,

My apologies for the delay.

The issue was followed up and identified: as opposed to continuous energy losses along a charged-particle step, discrete/point-like energy losses were not systematically considered for the generation of optical photons. Your low-energy-photon problem happened to be in a condition where the latter were significant.

This has now been corrected and the fix is planned to be included in the next major release scheduled for this month.

Thanks for your patience!




Dear Cesc and FLUKA experts,

Thank you very much for solving this issue and fixing it in the upcoming release.

Best regards,