Dear Agnieszka
If I am not mistaken you are using a rectangular beam when generating photons at 662 keV while starting from the decay of Cs-137 you will have an isotropic generation of emitted radiations. So primary particle will not have the same probability to reach the detector in both cases. I guess this explain most of the discrepancy.
Also as indicated in my previous email, the 662 keV photon is not coming from Cs-137 but by Ba-137m (populated at ~95 % from the decay of Cs-137), so for the sake of comparison of the two methods you may as well start with Ba-137m. To compare with a real life experiment you should of course start with Cs-137 (which will include both the contribution from Cs-137 and Ba-137m…)
Hoping this help.
Joachim
From: Agnieszka Witkowska [mailto:witkowskaagnieszka07_at_gmail.com]
Sent: 08 February 2018 22:38
To: Joachim Vollaire <joachim.vollaire_at_cern.ch>
Cc: FLUKA discussion <fluka-discuss_at_fluka.org>
Subject: Re: [fluka-discuss]: RADDECAY - problem with card usage
Dear Joachim,
Thank You for reply and help. I have the same structure of the .inp file as in your example, the only difference is that I am scoring the electrons by USRTRACK card.
I created two .inp files - one with RADDECAY card as a beam and another only with main energy line of Cs137 - 0.667MeV as a photon beam. In both cases I am interested in scoring the electrons in the ionization chamber volume.
Simulations of those two files give me completely different results. With RADDECAY card I obtained 7.3796116E-05 cm/pr and with main energy line 4.2062059E-02 cm/pr (I am scoring electrons in two regions - those are results only from the first one).
I do not understand where the differences in results come from, as I believe they shoud not differ as much.
I attached both .inp files and obtained results of the simulations.
Thank You for your support.
Best regards,
Agnieszka
2018-02-06 18:41 GMT+01:00 Joachim Vollaire <joachim.vollaire_at_cern.ch<mailto:joachim.vollaire_at_cern.ch>>:
Dear Agnieszka
It is not clear from your email (maybe you could send the input) what problem you are running. I assume you want to simulate the decay of Cs-137 (you are not specifying which isotope decay of Cs you are interested in…).
I have used an old input I have (it is not a point source in my case, but it is equivalent). Your input should have something like this :
BEAM 1.0ISOTOPE
BEAMPOS 0.0 0.15 0.0 0.24 0.0 CYLI-VOL
BEAMPOS 0.0 0.0 -0.125
HI-PROPE 55. 137.
*
RADDECAY 2.0
And you should adapt to what you want to score, but to see energy dependent spectra (maybe increase the energy upper limit) it could look like this:
* Now scoring particles entering the scoring box
*
DCYSCORE -1. PHO-FL1 PHO-FL1 USRBDX
*
USRBDX 1.0 PHOTON -55.0 CAPSIN CAPSUL1 1.0PHO-FL1
USRBDX 0.001 0.0 300.0 &
*
DCYSCORE -1. ELE-FL1 ELE-FL1 USRBDX
*
USRBDX 1.0 ELECTRON -55.0 CAPSIN CAPSUL1 1.0ELE-FL1
USRBDX 0.001 0.0 300.0 &
In my case it works fine (I have scored the energy spectra with the above cards), I checked with Cs-137 (which includes the decay of Ba-137m with FLUKA) or with Ba-137m itself and results are consistents (you see a continuous beta spectrum with end points at 514 and 1175 keV for Cs-137 emitted radiations and the gamma line at 662 keV from Ba-137m with some discrete electrons at 624 and 655 keV).
Greetings
Joachim
55-Cs-137 ENDF=551370; A=137; Z=55; Iso=0; Level=0[MeV]; Dmass=-86.55[MeV]; Hlife=9.49e+08[s]
J/P=7/2+; Abund=0; Htox=6.7e-09; Itox=1.3e-08; Stat=0
Decay modes:
BetaMinus Diso: 0 BR: 5.400% Qval: 1.1756
BetaMinus Diso: 1 BR: 94.600% Qval: 0.513596
=== Chain with 5.4 %
55-Cs-137 (5.4% BetaMinus) T1/2=9.49e+08
56-Ba-137
=== Chain with 94.6 %
55-Cs-137 (94.6% BetaMinus) T1/2=9.49e+08
56-Ba-137m
=== Chain with 94.6 %
55-Cs-137 (94.6% BetaMinus) T1/2=9.49e+08
56-Ba-137m (100% IsoTrans) T1/2=153
56-Ba-137
From: owner-fluka-discuss_at_mi.infn.it<mailto:owner-fluka-discuss_at_mi.infn.it> [mailto:owner-fluka-discuss_at_mi.infn.it<mailto:owner-fluka-discuss_at_mi.infn.it>] On Behalf Of Agnieszka Witkowska
Sent: 05 February 2018 22:02
To: FLUKA discussion <fluka-discuss_at_fluka.org<mailto:fluka-discuss_at_fluka.org>>
Subject: [fluka-discuss]: RADDECAY - problem with card usage
Dear Fluka Users,
I have some uncertainties regarding usage of RADDECAY card. I have read the Fluka manual and I cannot understand how RADDECAY card works in terms of beam spectrum. For example I would like to set up a beam as a spectrum of caesium. By setting it by RADDECAY card I obtain strange results and the spectrum seems to be "flat" - my assumption is that RADDECAY does not take into consideration data about number of particles from each energy interval. Can You please advise if I am right and how to solve that problem? Is there any chance to correct it without usage of user routines?
Thank You for your help in advance.
Best regards,
Agnieszka Witkowska
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Received on Fri Feb 09 2018 - 11:18:23 CET