RE: [fluka-discuss]: Co-60 source routine

From: Fabio Pozzi <fabio.pozzi_at_cern.ch>
Date: Fri, 13 Dec 2013 11:27:30 +0000

Thanks Alberto, actually I knew this and I have already tried. I guess that the way you mentioned is somehow time consuming because only about 2% of the total stories were emitted within my cone (0.21/4pi, where 0.21 is the solid angle of my cone) and the remaining 98% is lost in the blackhole. Therefore I preferred to write a source routine (which seemed to me the best compromise between statistics and needed simulation time).
Cheers,

Fabio

-----Original Message-----
From: Alberto Fasso
Sent: 13 December 2013 12:16
To: fluka-discuss_at_fluka.org
Cc: Fabio Pozzi; Mario Santana Leitner
Subject: RE: [fluka-discuss]: Co-60 source routine

Fabio,

in FLUKA it is possible to define directly a source made as a radioactive isotope. You can avoid all doubts about normalization in the following
way:

1) Define a BEAM card with SDUM = ISOTOPE and leave blank WHAT(1) and
    WHAT(2)
2) Define the radioactive isotope with command HI-PROPErt, WHAT(1) = 27
    and WHAT(2) = 60
3) Define a geometry with a cone of opening angle 30 degrees and vertex
    at the source location, and blackhole outside it. (Actually you can
    only use a truncated cone, so probably you need to put a small vacuum
    sphere around the source, intersecting the truncated cone).

Alberto

On Fri, 13 Dec 2013, Fabio Pozzi wrote:

>
> Hello Mario,
>
> I found out that the main problem is the normalization. Actually I did
> not take into account that I have not to use the total source activity
> for the normalization, but only the fraction that is emitted within
> the actual solid angle, i.e {15 GBq*omega/4pi} (where omega is the
> solid angle covered by my
> cone): this is the actual activity for the normalization.
>
> Moreover I have a further question: because of my energy sampling
> (once a photon of 1.17 MeV and once a photon of 1.33 MeV), should I
> also multiply by
> 2 in the end of the normalization? If I am not wrong this should take
> into account the photon yield of the Co-60 source (i.e. for each
> disintegration two photons are emitted).
>
>  
>
> Thank you for your help.
>
>  
>
> Cheers,
>
>
> Fabio
>
>  
>
> From: Santana, Mario [mailto:msantana_at_slac.stanford.edu]
> Sent: 12 December 2013 20:23
> To: Fabio Pozzi; fluka-discuss_at_fluka.org
> Subject: Re: [fluka-discuss]: Co-60 source routine
>
>  
>
> Fabio,
>
>  
>
> I checked that you had the right energies in your subroutine
> (typically an error of units, e.g. GeV instead of MeV could explain
> some discrepancies) and it seems OK. I am going to assume for now that
> the angular spectrum is fine although the implementation seems quite
> cumbersome (by the way, for best practice try to avoid mixing integers
> with real numbers, specially in ratios). Do dose rate maps look consistent with the emission angle?
>
> I guess the crucial point is the normalization. Which factor did you
> use to convert pSv/primary into mSv/h/15GBq?
>
>  
>
> Mario
>
>  
>
>  
>
> From: Fabio Pozzi <fabio.pozzi_at_cern.ch>
> Date: Thursday, December 12, 2013 9:35 AM
> To: fluka-discuss <fluka-discuss_at_fluka.org>
> Subject: [fluka-discuss]: Co-60 source routine
>
>  
>
> Dear all,
>
> I am simulating a Co-60 source emitting photons within a certain
> irradiation angle (30 degrees). I wrote a dedicated source routine
> which sample the emission direction and position according to my
> needs. This "seems" to work properly. In order to reproduce the two
> Co-60 photons I make my routine sample the photon energy with equal
> probability (0.5 each), i.e. once it chooses 1.17 MeV and once 1.33 MeV. I am scoring the dose-rate with USRBIN.
> The point is that when I normalize the FLUKA dose rate (which is in
> pSv/pr) to the source activity (15 GBq in my case) I obtain a dose
> rate at 1 m from the source around the Sv/h, instead it should be in
> the mSv/h range (cross-check with Nucleonica).
> If you have any idea/hints please let me know (I attached my input
> file and the source routine).
>
> Thank you in advance.
>
> Cheers,
>
> Fabio
>
>
>
Received on Fri Dec 13 2013 - 13:10:30 CET