I met a problem in using DOSE-EQ in USRBIN. I want to score kerma in water by trasmission photons from 450 keV electrons on a 100-micron tungsten target. To score kerma I set the transportation cutoff of electrons larger than the primary electron energy and photons of 1 keV. In USRBIN with ENERGY and DOSE the results seems reasonable, however, I tried DOSE-EQ, the result becomes much larger with much smaller error. To use DOSE-EQ for this calcualtion purpose may not be proper, but would anyone tell me what is the reason for getting this strange result with DOSE-EQ?
I’m not convinced that the answer by @xiaosj is exactly fitting your question.
The reason for the difference between the central value of the DOSE-EQ and the ENERGY scoring is simply the fact that these are different quantities. There is no reason for these to be equal.
The fact that the uncertainty on these is different instead derives from the different ways these are calculated. DOSE-EQ is calculated applying conversion factors to the track-length density. This means that a particle passing within a bin of your USRBIN contributes to the DOSE-EQ even if there is no interaction and no energy deposition, hence the different statistical uncertainty.
Once extra comment.
Setting an electron transport threshold in the water higher than the primary energy give the artifact that you see in your ENERGY and DOSE plots. The electrons enter the water, but since they are below threshold they are “killed” immediately and release their energy on the spot, i.e. your first bin, which in fact is much higher than all the others.
A045.inp (1.7 KB)