RE: [fluka-discuss]: study photon backscattering using FLUKA

From: Anton Lechner <Anton.Lechner_at_cern.ch>
Date: Sat, 27 Sep 2014 16:01:05 +0000

Dear Yuanjie,

It is not surprising that you find EM-CASCA to be much slower than NEW-DEFA since the applied electron/photon transport and production thresholds differ for these settings: for EM-CASCA, electrons/photons are transported down to 100 keV/10 keV, while they are only transported down to 1 MeV/333 keV in case of NEW-DEFA. In any case, I would recommend not to use NEW-DEFA, in particular since you have ~660 keV photons as source particles (for your application, electrons are not transported at all with the NEW-DEFA settings).
Apart from that, transport and production settings for electrons/photons can always be adjusted with the EMFCUT card (i.e. you can overwrite the predefined settings of the DEFAULTS option).

Secondly, concerning the difference between air and concrete. When running your input file (with EM-CASCA) and looking at the bins close to the wall I see an increase in equivalent-dose (by about 10%) and photon fluence (by about 30%). Of course, in both cases dose and fluence are dominated by the incoming photons, but still there is an increase if one uses concrete instead of air (due to backscattering). Maybe you did not run enough primaries to appreciate the differences? (I ran several 1E9 primaries in both cases).

Cheers, Anton




________________________________________
From: owner-fluka-discuss_at_mi.infn.it [owner-fluka-discuss_at_mi.infn.it] on behalf of 毕远杰 [biyuanjie_at_tsinghua.org.cn]
Sent: 25 September 2014 14:40
To: fluka-discuss
Subject: [fluka-discuss]: study photon backscattering using FLUKA

Dear fluka users,

I am using FLUKA to study the backscatting of the concrete wall from Cs137 source.
The source is put 3.5m from the wall. I expect to get different dose when the material of the wall is set to concrete and air, but I did not.
I attached my input file and have some questions of the setting:
1. The Defaults: Should I use EM-CASCA or NEW-DEFA? EM-CASCA is much slower than NEW-DEFA.
2. I can find the fluence difference, but no dose difference when using EM-CASCA. But when I use NEW-DEFA, both the fluence and the dose have no difference.

I am looking for a reply from the experts.

Many thanks and best wishes
Yuanjie
Received on Sat Sep 27 2014 - 19:57:46 CEST