Date: Tue, 28 Mar 2017 07:51:02 +0000
Dear experts,
In my pursuit to calculate the 192Ir dose distribution in the Zubal head phantom using Fluka code I got stuck again - this is time in calculating the dose rate constant. As no external help available for me locally, I would appreciate any insights or comment from you.
As it is stated, the dose rate constant Λ (cGy/U-hr) is defined as the dose rate to water at a distance of 1 cm on the transverse axis of a unit air kerma strength source in a water phantom.
So it is necessary to measure both the reference air kerma rate at 100 cm and the absorbed dose rate to water at 1 cm distance from the source perpendicular to the source axis
I modelled the seed geometry and usrbin-ed the dose values in 150 cm radius sphere, filled with air and later- filled with water. In the air sphere the dose rate at 100 cm from the seed approx. 2.7E-17 Gy per decay that more less is what can be expected (400GBq would give ~39 mGy/hr in comparison with expected ~45 mGy/hr)
The dose rate in the water sphere at distance 1 cm from the seed surface is around 1.2E-13 Gy per decay. So here I stuck - ther ref value for dose rate constant for 192Ir seed should be approx. 1.1 cGy/(U-hr). How to combine all this data to something like that?
I assume there is a certain "obvious" thing I am missing, due to lack of experience.
Input files are attached in case it is interesting. Dose rate values are scored in usrbin R-phi-z mesh then plotted as type 1D Max in Flair on R axis. However I tried many other options including setting detectors regions, etc. I also noticed that energy spectra is missing ~1.4 MeV spike in comparing with spectra from MCNP but maybe this is not related or there is other explanation for this.
Regards
Alex
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- application/octet-stream attachment: IR192_k1.inp
- application/octet-stream attachment: IR192_k2.inp
(image/jpeg attachment: ir192_spectra.jpg)