Re: O-16(gamma, alpha)C-12 and N-14(gamma, p)C-13 cross sections below 9MeV

From: Paola Sala <paola.sala_at_mi.infn.it>
Date: Thu, 18 Jul 2013 11:20:18 +0200 (CEST)

Hello
in addition to what Alberto said,
please take into account that we are implementing important modifications
to one of the models mentioned by Alberto - the Fermi breakup . These
modifications affect exacly the observables you are interested in.
Preliminary results have been presented at the Varenna conference last
year
http://cds.cern.ch/record/1537387/files/p469.pdf, where you find results
for gamma-x partial cross sections on carbon.
  The updated fermi-breakup is NOT included in the presently distributed
version, will be available with the next release.
Greetings
Paola

> Hi George,
>
> for photonuclear reactions, FLUKA uses only TOTAL cross sections: it uses
> them
> to determine the point of interaction. The interaction is simulated by one
> or
> more models ("event generators"): evaporation, pre-equilibrium, Fermi
> breakup,
> etc.) The particular partial reaction, in your case (gamma,p) or
> (gamma, alpha), is the result of the event generator, not the input to it.
> So, to answer your first question: what you find with your "experiment"
> are not
> the cross-sections "used" by FLUKA, but the cross sections "calculated" by
> FLUKA. The only cross sections used are the total ones (gamma,n + gamma,p
> +
> gamma,alpha, + gamma,2n + gamma,pn,....)
>
> In answer to your second question, if those cross sections significantly
> differ
> from the experimental data (I hope not!) the only way to change your
> results
> would be to change the models, which is obviously impossible. There are no
> partial cross sections available in the code, so none that can be changed.
>
> You can still calculate photon energy spectra, and fold them with the
> cross sections you prefer, but I don't think that this is what you are
> looking for.
>
> Alberto
>
> On Tue, 16 Jul 2013, George Kharashvili wrote:
>
>> Dear FLUKA experts,
>>
>> We are interested in O-16(gamma, alpha)C-12 and N-14(gamma,p)C-13
>> reactions
>> below 9MeV. We set up FLUKA models with thin targets and
>> "experimentally"
>> determined the cross-sections. Sample input file and derived
>> cross-sections
>> are attached.
>>
>> The model is simple: photon beam is incident on 1% radiation length
>> target.
>> Photon and e-/e+ production and transport thresholds are set to 20 keV
>> below
>> the beam energy. Number of alphas is scored in the target region. This
>> is
>> repeated for beam energies between 7.2 and 9.2 MeV in 20 keV steps.
>>
>> We would like to know:
>> 1. If this is the best way to find out the cross-sections used by FLUKA;
>> 2. If we determine that the cross-sections in FLUKA significantly differ
>> from the experimental data, is there a way to run FLUKA using our custom
>> tabulated cross-sections.
>>
>> Thank you in advance for your time.
>>
>> -George Kharashvili
>
>


Paola Sala
INFN Milano
tel. Milano +39-0250317374
tel. CERN +41-227679148
Received on Thu Jul 18 2013 - 12:30:05 CEST

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