Dear all,
I wish to replicate a dose rate experiment in FLUKA that includes a 60kVp X-ray source and a dosimetre that outputs Air Kerma rate. My input file is attached.
The experiment was done with a solid state dosimetre that measured Air Kerma. I do not have the effective volume and material of the dosimetre medium therefore I can not replicate the physical processes of the dosimetre. However I can measure Air kerma directly. I also have a conversion factor to convert the fluka results from 1/primary to 1/s. This simulation's purpose is to confirm the conversion factor is correct.
To measure Air kerma I am firing the X-ray source in air and measure the dose in an air region that stands at 10.7cm distance from the source(this is equal to the SDD of the experiment). I have set electron transport threshold to 1GeV inside the region so that all secondary electrons are detected by my REGION DOSE-EM USRBIN. I also made sure that secondary electrons from outside the detector region do not enter it by having a 1GeV transport threshold too(discarding them would be faster, wouldn't it?).
From my REGION DOSE-EM USRBIN I am expecting values in GeV/g/primary as stated in the FLUKA manual. However the values are linearly dependent on the volume of the region. Given that my X-ray source is divergent I would of course expect some Air Kerma variation with different region volumes but not as much as a linear dependence. The region sizes I have used are 2cm, 1cm, 0.5cm cubes. I tried those sizes because the dosimetre effective detector volume looks like it is of that order of magnitude.
My questions are:
1. Can I actually compare the simulation with that experiment since no dosimetre information is known other than its Air Kerma measurement? In the literature i've seen people using ambient dose equivalent which has standard volumes and masses.
2. If I can compare, how would I choose the region size in the simulation? Maybe score dose rate at a point?
3. Why does the REGION DOSE-EM USRBIN result increase linearly with increase of region volume? Isn't it supposed to be normalised per mass thus indirectly per volume?
p.s. It just happens that the Air Kerma rate in a region of 2x2x2cm3 is within the error bars of the measured one but i guess this is just a coincidence.
Best regards,
Thomas Primidis
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- chemical/x-gamess-input attachment: HVL.inp
Received on Fri Jun 14 2019 - 16:09:44 CEST