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Forum: Hadronic Processes
Re: Question neutron stimulated gamma spectrum (Tuoyu Cao)
Re: None Re: neutron stimulated gamma spectrum (Koi, Tatsumi)
Date: 23 Jan, 2013
From: Tuoyu Cao <Tuoyu Cao>

Thanks a lot for reply.

I am not sure the cross section you used here is for inelastic scattering only. And the number 20 is the number of gammas on 847keV peak, not the total number of interactions.

I use Shielding physics list here. I guess it also uses NeutronHP for neutron interatctions. When the concentration is relatively high, say 6000PPM or higher, I see similar result as you saw. The absence of Cu does not affect Fe spectrum a lot. But when the Fe concentration is low, say around 60PPM, I can see strong effect from Cu contamination. (see attached)

Moreover, at low concentration, there is no linear relationship between Fe concertration and number of gammas on the peak. You can see when the concentration increases from 60ppm to 6000ppm, the number of gammas only increase from 20 to 60(see attached)

So it seems like a problem for low concentration situation.

Thanks a lot for any explanation.

Tuoyu

On Sat, 19 Jan 2013 00:46:07 GMT, Koi, Tatsumi wrote:

> Let' me play some numbers 
> 
> water  1cm3 -> 1g
> Fe 60PPM -> Fe 6.0E-5 [g]
>          -> Fe ~6.5E17 atoms
> XS of n + Fe -> 1st Fe* is about ~1 barn at 2.5MeV
> Probability of the reaction per neutron (at the energy) is ~6.5E-7.
> Estimate number of the reaction for 1M is ~0.65.
> But you have 20 for the number. 
> This difference is relatively large.
> 
> For testing purpose, I enhanced for the contamination level of Fe and Cu to 6000PPM and 2000PPM respectively and comparing the energy spectra, I do not have a lot difference between them. So I could not reproduce your problem. I used the NeutronHP for this. 
> 
> Tatsumi
> 

   Attachment:
      http://hypernews.slac.stanford.edu/HyperNews/geant4/get/AUX/2013/01/23/08.50-98604-Water_60ppmFe.gif
      http://hypernews.slac.stanford.edu/HyperNews/geant4/get/AUX/2013/01/23/08.50-49831-water_60ppmFe_60ppmCu.gif
      http://hypernews.slac.stanford.edu/HyperNews/geant4/get/AUX/2013/01/23/08.50-81472-water_90ppmCu_60ppmFe.gif
      http://hypernews.slac.stanford.edu/HyperNews/geant4/get/AUX/2013/01/23/08.50-14183-water_6000ppmFe.gif
      http://hypernews.slac.stanford.edu/HyperNews/geant4/get/AUX/2013/01/23/08.50-53797-water_20000ppmFe.gif

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1 None: Re: neutron stimulated gamma spectrum   (Koi, Tatsumi - 23 Jan, 2013)
1 Question: Re: neutron stimulated gamma spectrum   (Tuoyu Cao - 29 Jan, 2013)
2 None: Re: neutron stimulated gamma spectrum   (michel maire - 24 Jan, 2013)
1 None: Re: neutron stimulated gamma spectrum   (Koi, Tatsumi - 28 Jan, 2013)
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