Dose Eq. Simulation

test.inp (25.3 KB)
calculations_test.pdf (378.7 KB)

Dear FLUKA Experts,

I am simulating Dose Eq. at the surface of the geometry in the input file.
At Z=29.4 to 30.4, as I move from x=0 to x=11, the dose eq. value should decrease. But while simulating it in FLUKA, the dose eq. value decreases till x=7, but again increase from x = 7 to 10. Why is it so?

Please guide.

With regards,

This is the logical effect of the air gaps you modeled at r = 8.3 and 9.3 cm in the forward part of your geometry.
Best wishes

Dear Francesco,

I filled the air gap: i) with SS and ii) with Lead.
In both cases, pattern is still the same.

Is it due to sudden density changes? Please guide.

With regards,

If you fill the air gaps with stainless steel, the result is not the same:

Still, the persisting rise beyond r = 7 cm is due to the fact that stainless steel provides a photon absorption significantly inferior to lead and tungsten, related to its lower density and especially average atomic number. If you replace it with lead, including the ss1 to ss19 regions!, that feature disappears:

(Note that my statistics is limited to half a million simulated histories in total, to be suitably increased as in your input).

test_2.pdf (391.1 KB)

I also obtained the same results as yours in FLUKA. However, I ran the same simulation in MCNPX, the dose rate decreases from r = 0 to 11 (no increase in dose rate near the air gap).

Then you should inquire in the MCNP forum why your MCNP simulation does not display the expected gap effect.