Re: [fluka-discuss]: comparison of photon fluence from mgdrawBDX and USRBDX

From: Fasso, Alberto <>
Date: Wed, 9 Sep 2020 07:44:46 +0000

Dear Riya Dey,
the ratio between the USRBDX results and that obtained by you with mgdraw is nearly exactly 2. Therefore, it is obvious that with mgdraw you have not scored fluence, but current.
See any of the FLUKA course lectures:
"In an isotropic field can be easily seen that on a flat surface
J = /2"
Indeed, did you take into account the cosine of the crossing angle? It is not an easy task, especially for grazing particles
crossing the boundary. One important lesson you should learn is to trust the built-in FLUKA scoring algorithms, which are nearly always much better than what you can try to do by
yourself with mgdraw or other user functions


From: <> on behalf of Riya Dey <>
Sent: Wednesday, September 9, 2020 5:54 AM
Subject: [fluka-discuss]: comparison of photon fluence from mgdrawBDX and USRBDX

Dear FLUKA experts,

In a simulation, mgdrawBDX has been used to obtain photon distribution from void to target. The total no of data point obtained is 243341 for 5E+9 primaries (no of history = 1E+8, spawn = 10, cycle = 5). Then from this information, photon fluence is 4.86682E-5 particle/primary.

At the same time I have used USRBDX card with one way scoring from void to target and fluence is ( --> (Part/pr) 9.6862677E-05 +/- 0.3224583 % ).

From my understanding, these two numbers should match.

Can you please guide me in this matter ?

Thanks and Regards

Riya Dey

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Received on Wed Sep 09 2020 - 09:44:46 CEST

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