Hello
The input needs to be better tailored to your problem:
The input does not include any DEFAULTS or EMF-CUT card. As a consequence,
the production and transport thresholds are set according to the default
"DEFAULT":, which means NEW-DEFA, which sets the photon transport
threshold to 300 keV. No photon below that energy will be transported.
The threshold settings can be chacked in the output file, the FLUKA
output, not the flair one. The FFLUKA output is obtained for each cycle
and has the cycle number in it. In your case mu_original001.out for the
first cycle. There you'll see
PMMA
Rho = 1.19000 g/cm**3 Rlc= 34.0748 cm
Ae = 1.51100 MeV Ue = 5061.25 MeV
Ap = 0.333333 MeV Up = 5060.74 MeV
Ae and Ap being the thresholds for electrons and photrons, in MeV, total
energy.
You can either include a DEFAULT card with SDUM=PRECISIO, and/or add two
EMF-CUT cards for production and transport of electrons and photons. I
would suggest to add in any case a DEFAULT=PRECISION, because it activates
precision effects important at low energies. With it, the electron
threshold ids set to 100 keV, and the phorton one to 33 keV.
Regards
Paola
> Dear Fluka Experts,
>
> I am using USRBDX to obtain the mass attenuation coefficient for some
> polymers like PMMA , using photons with energies from 50 keV to 150 keV.
> Before using it in the geometry that I am building, I wanted to test the
> method in a simpler input. I am using the input provided by user Andrea
> Fontana from this discussion
> http://www.fluka.org/web_archive/earchive/new-fluka-discuss/11329.html
> (mu_orignial.inp).
>
> It works well for energies above 400 keV, with the resultant mass
> attenuation coefficient value being very close to NIST, but below that it
> detects 0 particles on the estimator that goes from the sample to the
> vacuum around (24 BIN), as it shows in the file mu_original_24_sum.lis,
> with any different thickness of material that I try .
> By Lambert-Beer Law, and using NIST value of mass attenuation coefficient
> for PMMA (pho= 1.19 g/cm³) 1.456E-01 cm²/g, with 2.5000002E-03 part/cm²/pr
> of incident intensity, thickness of 0.1 cm,
> I should be detecting around 2.10E-03 part/cm²/pr of transmitted
> intensity
> for 150 keV, but it detects 0.
>
> There are no error messages in the compilation. I don't understand why
> this
> is happening, can you please help with this issue?
>
> Regards,
> Samuel
>
Paola Sala
INFN Milano
tel. Milano +39-0250317374
tel. CERN +41-227679148
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Received on Mon Aug 24 2020 - 11:45:21 CEST