R: Re: R: Re: [fluka-discuss]: Neutrons on carbon still

From: <francesca.belloni_at_libero.it>
Date: Thu, 6 Aug 2015 10:35:05 +0200 (CEST)

Dear Francesco,

       thanks a lot for your reply!

Cheers,
Francesca


>----Messaggio originale----
>Da: Francesco.Cerutti_at_cern.ch
>Data: 05/08/2015 23.39
>A: "francesca.belloni_at_libero.it"<francesca.belloni_at_libero.it>
>Cc: "FLUKA discussion"<fluka-discuss_at_fluka.org>
>Ogg: Re: R: Re: [fluka-discuss]: Neutrons on carbon still
>
>
>> About the last point you mentioned, does it mean that since the charged
>> particles
>> by low energy neutrons are not generated I can not score the energy they
>> deposit in the diamond,please?
>
>You can score energy deposition in the detector, but this is just the
>kerma associated to a neutron of a given group energy interacting in
>natural carbon (taking into account on average the contribution of
>charged products). If the detector size is such that the transport of
>charged products is in fact negligible, then you will get a meaningful
>average value. But anyway an event-by-event study (pulse height spectrum)
>is not possible, so I'm afraid that your goal is out of question.
>
>Ciao
>
>Francesco
>
>**************************************************
>Francesco Cerutti
>CERN-EN/STI
>CH-1211 Geneva 23
>Switzerland
>tel. ++41 22 7678962
>fax ++41 22 7668854
>
>On Wed, 5 Aug 2015, francesca.belloni_at_libero.it wrote:
>
>> Hi,
>>
>> thanks a lot!!!
>>
>> I was so sure I was shooting 18 MeV neutrons that I did not checked that at
>> all...
>> Thanks also for all the explanations.
>> The final goal of the simulations would be to reconstruct the response of
the
>> detector to
>> an incident neutron beam.
>> About the last point you mentioned, does it mean that since the charged
>> particles
>> by low energy neutrons are not generated I can not score the energy they
>> deposit in the diamond,please?
>>
>>
>> Thanks really a lot!
>>
>> Regards,
>> Francesca
>>
>>
>>
>>
>>> ----Messaggio originale----
>>> Da: Francesco.Cerutti_at_cern.ch
>>> Data: 05/08/2015 18.58
>>> A: "francesca.belloni_at_libero.it"<francesca.belloni_at_libero.it>
>>> Cc: "FLUKA discussion"<fluka-discuss_at_fluka.org>
>>> Ogg: Re: [fluka-discuss]: Neutrons on carbon still
>>>
>>>
>>> Hi Francesca,
>>>
>>> you believe to shoot a 18 MeV (kinetic energy) neutron, whereas you are
>>> shooting a 18 MeV/c (momentum) neutron, which - as written in the
>>> quite useful Beam properties section of the output - has a kinetic energy
>>> of 170 keV. So we are in a region (group #144) where one just expects
>>> capture (apart from elastic), indeed yielding 13C (on 12C) and 14C (on the
>>> small fraction of 13C).
>>>
>>> Note also the following:
>>>
>>> - your interpretation of the residual nuclei probabilities is wrong, see
>>> http://www.fluka.org/web_archive/earchive/new-fluka-discuss/6203.html
>>>
>>> - you are in the world apart of low energy neutrons (also at 18 MeV
>>> kinetic energy), based on library data and not on models. This means that
>>> EVAPORAT and COALESCE are totally pointless. And also LAM-BIAS does not
>>> apply (pointless too), as you can realize looking at the (missing) effect
>>> on number (vs weight) of performed low-energy neutron interactions and CPU
>>> time.
>>>
>>> - additionally, as a continuation of the above point, remember that -
>>> apart from very few exceptions - charged particles (including residual
>>> nuclei) by low energy neutrons are not generated explicitly and so cannot
>>> be transported (IONTRANS pointless). You can ask FLUKA to evaluate the
>>> production rates of low energy neutron reaction residues, but these do not
>>> exist as particles in the simulation. The adopted group-wise treatment
>>> prevents from simulating exclusive reaction channels.
>>>
>>> Ciao
>>>
>>> Francesco
>>>
>>> **************************************************
>>> Francesco Cerutti
>>> CERN-EN/STI
>>> CH-1211 Geneva 23
>>> Switzerland
>>> tel. ++41 22 7678962
>>> fax ++41 22 7668854
>>>
>>> On Wed, 5 Aug 2015, francesca.belloni_at_libero.it wrote:
>>>
>>>> Dear all,
>>>>
>>>>        I am still trying to get alphas out of n+diamond_material
>> interaction, but with no
>>>> success.
>>>> So I switched to another code and for a 5 m thick diamond, I get alphas
>> (and other heavy
>>>> ions).
>>>> Then I went back to FLUKA and reduced the input at the minimum: only a
>> diamond 500 cm
>>>> thick and neutrons striking it.
>>>> I asked RESNUCLEI in the diamond region, but I only get C13 and C14, as
>> product of n+natC.
>>>> Could anyone give a look, please?
>>>>
>>>> If I look at the output file everything seems to have been activated
>>>> In my *.inp LOW-NEUT, WHAT(4)=4 asks for a printout of  the information
>> about the residual
>>>> nuclei. This is dumped on the *.out file.
>>>>
>>>> If I look at my *.out file I see that the neutrons I am shooting belong
to
>> the Neutron
>>>> (low energy)
>>>> Xsec group number 5:
>>>>
>>>>
>>>> Neutron group n.:    5  upper limit 1.8221E-02 GeV,  average energy 1.7995
E-
>> 02 GeV,
>>>>                                   velocity 5.7846E+09 cm/s,  momentum
1.8477
>> E-01 GeV/c
>>>>
>>>>  
>>>> Later on, on the same *.out file, there is written that the FLUKA medium
>> number 26
>>>> corresponds to the Xsec medium number 1.
>>>>
>>>>
>>>>    Fluka medium     Name     Xsec medium  atomic density          Id.
>> 1        Id.
>>>> 2        Id. 3
>>>>      number                   number     ( at/(cm barn) )
>>>>
>>>>          1        BLCKHOLE         0         0.0000
>> E+00               0           
>>>> 0            0
>>>>
>>>>          2        VACUUM        1000         0.0000
>> E+00               0           
>>>> 0            0
>>>>
>>>>         26        DIAMOND          1         1.7649E-
>> 01               6          
>>>> -2          296
>>>>
>>>>
>>>> Going down again in the *.out file there is written:
>>>>
>>>>  Residual nuclei informations for medium    1
>>>>
>>>>   Group:    1   A     Z    Prob
>>>>
>>>>               12     6    7.54E-01
>>>>               11     5    9.09E-01
>>>>               13     6    9.09E-01
>>>>               12     5    9.36E-01
>>>>                9     4    1.00E+00
>>>>               14     6    1.00E+00
>>>>                1     1    7.44E-02
>>>>                2     1    1.07E-01
>>>>                4     2    6.44E-02
>>>> [..]
>>>>
>>>>  Group:    5   A     Z    Prob
>>>>               12     6    7.87E-01
>>>>               11     5    9.11E-01
>>>>               13     6    9.12E-01
>>>>               12     5    9.48E-01
>>>>                9     4    1.00E+00
>>>>               14     6    1.00E+00
>>>>                1     1    4.18E-02
>>>>                2     1    1.18E-01
>>>>                4     2    5.25E-02
>>>>
>>>>
>>>> Therefore it means that in FLUKA the neutrons I am shooting have a
certain
>> probability
>>>> (different from 0.0)  to interact with the diamond and give alphas,  Be-
>> 9,  B-11 and B-12.
>>>>
>>>> I thought it could have been a problem of statistics (I shoot 9E+7
neutrons
>> on a material
>>>> where lam-bias=-0.001) . But looking at those probabilities, it seems
it's
>> more likely to
>>>> get B-12 than C-13  (IF i am understanding the table correctly...which is
>> not sure).
>>>>
>>>> But I get C-13 and C-14 only.
>>>>
>>>>
>>>> What am I missing,please?
>>>>
>>>> Thanks,
>>>>
>>>> regards,
>>>>
>>>> Francesca
>>>>
>>>>
>>>>
>>
>>
>>


__________________________________________________________________________
You can manage unsubscription from this mailing list at https://www.fluka.org/fluka.php?idc_info
Received on Thu Aug 06 2015 - 12:02:00 CEST

This archive was generated by hypermail 2.3.0 : Thu Aug 06 2015 - 12:02:04 CEST