HI,
I’m trying to measure the kerma in air for an F18 source. I used the USRTRACK card to obtain the fluence which I then use with an external python script to calculate the kerma by multiplying by the energy and the (μ(E)ρ) e integrating as per the formula:
K=∫Emax0dΦ(E)dE⋅(μ(E)ρ)⋅EdE
However, the results they obtain differ a little from what I expect. I don’t know if there’s something wrong.
Thank you
prova.flair (1.8 KB)
This is the file
Dear Andrea,
thank you for your question. Please consider that, due to my involvement in the on-going FLUKA course, my answer might be delayed.
In the meantime, would you mind sharing your integration script (even privately, if you prefer) and quantifying the discrepancies that you observe (i.e.: is it something surely beyond statistical uncertainty?) ?
I will review your input file soon.
Best regards,
Tommaso
If it helps, I’ve run this simulation for several radionuclides and only had this problem for F18. I think the problem could be the fact that the photons generated by the F18 are due to the annihilation process of the positrons emitted during decay.
Dear Andrea,
I would suggest setting to air also the space between the source and the scoring volume. You could also verify that your AIR material description matches the one used for the conversion factor computation you are referencing.
As usual, I would then work on transport thresholds, normalisation, and statistics of the run.
As you have already understood, in your current setup, the photon spectrum is essentially a delta function at e+/e- annihilation energy.
Best regards,
Tommaso
Other resources on the forum: