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

From: Alberto Fasso' <fasso_at_SLAC.Stanford.EDU>
Date: Wed, 17 Jul 2013 02:40:13 -0700 (PDT)

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
Received on Wed Jul 17 2013 - 14:23:07 CEST