Hi Sanjay,
I double checked for the N gamma emission line, and the bad news is that there’s not gonna be a line in the simulation.
FLUKA uses normally a multi group approach for the low-energy neutrons and gamma generation. Down scattering matrixes provide the probability for neutrons in a given energy group (260 groups available) to generate a photon in another specific energy group (42 photon energy groups available). For few materials there a more detailed model when the photon energy can be sampled, but I realises it’s just in FLUKA development version and this feature it’s not available for nitrogen. The gamma will be generated and score in the 5-th group whose energy goes from 10 to 12 MeV.
The group structure implemented in the released code can be found in chap.10.4.1.1 of the manual (‘energy group structure of the 260-neutron, 42-gamma groups’)
Sorry for the problems my initial response might have generated.
Best,
Vittorio
> On 27 Nov 2016, at 13:32, Vittorio Boccone <dr.vittorio.boccone_at_ieee.org> wrote:
>
> Hi Sanjay,
> as I said the 10.8MeV gamma line from N neutron capture will be typically 100-1000 smaller (in terms of magnitude) then the hydrogen line
> Apply a proper binning and to use the adequate statistic, the peak will appear. Plot also the statistical error of you simulation vs. the number of primaries to evaluate how many primaries you will need to run to reduce the error such that the peak will appear.
> http://iopscience.iop.org/article/10.1088/1742-6596/763/1/012011/pdf
> Best,
> Vittorio
>
>
>> On 27 Nov 2016, at 13:29, sanjay andola <andolas.007_at_gmail.com> wrote:
>>
>> Thanks
>> Yes these plots are usrtrk plots at BGO detectors, to check the difference for in the Nitrogen lines, I have used the graphite as a sample too. However the difference in spectrum in both the cases seems due to statistical. Do I need to use other physics/transport/biasing cards to get the results.
>>
>> Sorry for the typo error in earlier mail , it was "I have found no significant in the two fluence curves ".
>>
>>
>> On Nov 27, 2016 5:46 PM, "Vittorio Boccone" <dr.vittorio.boccone_at_ieee.org> wrote:
>> Dear Sanjay,
>>
>>> I am looking for thermal neutron capture gamma rays in the nitrogen containing substance urea. I am expecting the nitrogen capture gamma line of 10.8 MeV like 2.22 of
>>> H capture in the fluence curve. for comparison I have simulated for the Graphite. However I found so significant difference in there two fluence curves. am I doing it wrong or do I have to run more number of histories..
>> It’s not clear what the plot is. Are those results of the BGO user track?
>>
>> The 10.8MeV gamma line from N neutron capture will be typically 100-1000 smaller (in terms of magnitude) then the hydrogen line, therefore you need to apply a proper binning and to use the adequate statistic.
>> http://iopscience.iop.org/article/10.1088/1742-6596/763/1/012011/pdf
>>
>> Check the statistical error for the simulation. I would add also a few other USRBDX to check the spectrum at different locations.
>> Best,
>> Vittorio
>>
>>
>> P.S. you have errors in the geometry which involve the RPP “Floor” which is probably not remove from the region “Air"
>>
>>
>
__________________________________________________________________________
You can manage unsubscription from this mailing list at
https://www.fluka.org/fluka.php?idc_info
Received on Sun Nov 27 2016 - 23:42:10 CET