Simulated Dose Comparison with Experimental

Hi everyone,

I have been doing simulations for a 6 MeV LINAC. For this I need to score dose rate. I get energy deposited through usrbin card and then convert it to dose rate incorporating our Pulse width and pulse repetition frequency. But the dose i get through simulation is much less than the dose we measure in lab at 6 MeV LINAC.

So, my question is can we get exact absolute dose through FLUKA Simulations?

Dear @anum.asif,

Did you normalized your results? Fluka results are given per single primary particle.

Dear @amario yes. I considered my result as energy deposited per particle(electron).

Dose per primary particle or electron (Gy/primary)= Energy deposited/primary particle*1.602E-7

Number of electrons/pulse(4 µs) for 100 mA current= 100mA*4 µs/1.6e-19C= 2.5E12 electrons

average dose/pulse= Dose per electron* number of electrons/pulse

Dose/second = Dose per pulse* Pulse repetition frequency(PRF-Hz)

In this way, when I get dose rate which is not equal to the measured dose in lab.

Per region [GeV] or through a regular mesh [GeV/cm^3]?

This does not check out: if you multiply GeV/primary (or GeV/(cm^3 primary), see above) by 1.6E-7 mJ/GeV, you get mJ/primary (or mJ/(cm^3 primary)), which is not a dose. The density [g/cm^3] of the scoring material has to be included in the equation.

Dear @ceruttif ,

Thank you for addressing my question.

1)It is a regular mesh in Cartesian coordinates.

  1. Yes I am considering density as well But as I am scoring dose in water and its density is 1g/cm3 that’s why I didn’t write here the density number.

What is the difference that you see?
What are the uncertainties on the results of the measurements and of the simulations?
Did you take into account the volumes?

Also, it would be good if you could share your input.

Dear @amario,

I get dose deposited about 10 cGy/min after calculation but in actual for 100 HZ PRF with 100 mA current, we measure 80 cGy/min dose in lab. I am sharing here my input file.
Linac6.flair (5.2 KB)

In the BEAM card, you implemented an isotropic source, irradiating over 4pi, which is not a beam directed towards your setup.

Dear @ceruttif what specifications should I use in the beam card?? As I have a beam spot of 6MeV electrons coming out from electron gun. The diameter of beam spot is 3mm with guassian distribution.

Dear @anum.asif,

Have you tried looking at the Simple Source lecture from the last course for beginner?
Or at the BEAM card manual?
There it is well explained how to define a simple beam like the one you want to simulate.

Dear @amario,
Thanks,
I will look into them. I hope this solves my problem.