We are trying to compute the absorbed dose in our region of interest resulting from a proton beam (energy considered is between 10-18 MeV in steps of 1 MeV). In terms of intensity of beam we have a pulsed beam of 70nA in 10ns. We are interested in the value of the absorbed dose only per pulse.
We used the USRBIN card scoring DOSE and we are struggling a bit with the normalization that should be used in order to obtain the absorbed dose in Gy/pulse from the results given by fluka in GeV/g.
As far as we understood from the manual and from doing a bit of reading on the forum we are thinking that the normalization factor should be like this:
NF = 1.602E-07 (so that we go from GeV/g to Gy/s) * Intensity of beam [in particles/s] * pulse duration [in seconds]
We transformed the intensity from nA per pulse like this: (70E-09*10*10E-9)/(1*1.6E-19) so that we obtain the intensity in particles/s.
So in the end would be:
Absorbed Dose = Value from fluka * 1.602E-07 * ((70E-09*10*10E-9)/(1*1.6E-19)) * (10E-09)
In this correct?
Bellow you can find the .flair project, .flair input
Any assistance or guidance is highly appreciated.
Input files
Please upload all relevant files. (FLUKA input file, Flair project file, user routines, and data files)
There is a double mistake here: 10 ns should read 10E-9, and not 10*10E-9 (which gives 1e-7), and the resulting value represents the pulse intensity in protons, and not the pulse current in protons/s! [ A * s / (C/p) = p ].
Multiplying by 1.602E-07 (which by the way cancels out the above identical term, apart from the power of 10) you go from GeV/g (FLUKA result per primary particle) to Gy, and not Gy/s.
No, since you multiplied twice by the pulse duration.
Note that the FLUKA result for DOSE is in GeV/g per primary particle in case of a regular USRBIN mesh (such as the Cartesian mesh X-Y-Z you adopted), while in case of scoring by Region it is in GeV/(g/cm^3) and it has to be further divided by the region volume in cm^3.
Yes, if applied to the FLUKA DOSE value resulting from the Cartesian (or cylindrical) USRBIN mesh (for the USRBIN region scoring, the region volume has to be included too).
Note that 1.602 and 1.6 are exactly the same number.
Also, the dose result may be extremely sensitive to the adopted spatial resolution, especially in case of a (unrealistic) pencil beam, which by definition implies an infinite dose value at the impact point.