Hi:
I have most recently been using G4 to measure the dose rate parameters of our newly designed radioactive sources, but now I am having some problems with the dose rate measurements.
We designed the I-125 radioactive source activity of 0.5mCi, according to the formula this 0.5mCi radioactive source can produce 1.85*10E8
decays per second. I used G4 with/run/beamOn 185 , 1850 and 18500
particles respectively.
And counting the absorbed doses in SD, I found that these absorbed doses basically showed a linear relationship. So I used the command /run/beamOn 185000
in the final experiment and multiplied the absorbed dose by 1000 to get the absorbed dose of 5mCi I-125 in the detector in one second.
But I don’t know if this method of mine is feasible, so I would like to ask for your advice. Also I have another question.
I see more in some papers that use MCNP
to calculate absorbed dose, they use MCNP *f4 tally
to calculate energy fluence (MeV/cm2)
and then use mass-energy absorption coefficients
to convert energy fluence to absorbed dose rate.
According to my understanding, I count the absorbed dose of SD in one second in G4, so that I can get the absorbed dose rate in Gy/s
, and then I multiply this value by 3600 to get the absorbed dose rate in Gy/h
.
Based on the above description my questions are as follows:
The first question is whether I can conclude that G4 shows a linear relationship when counting the absorbed dose, such that I can use the command /run/beamOn 185000000 instead of /run/beamOn 185000 or even less and multiply it by the corresponding multiplier.The resulting absorbed dose rate of SD in one second was obtained.
The second question is whether the way I calculated the absorbed dose rate using G4 is correct, which is to first derive Gy/s
and then multiply by 3600 to get Gy/h
.
The third question is whether there is a big difference between the absorbed dose rate calculation method of MCNP
and the absorbed dose rate counted by G4
. If my absorbed dose rate calculation method is correct is it possible that there is not much error between these two.
Thank you all for your responses.