Re: cross sections of production: comparison with literature

From: Paola Sala <>
Date: Wed, 15 Jul 2009 13:57:39 +0200 (CEST)

Dear Francesca
I had a first look at your results, and compared with what I get by
running the event generator and using the RESNUCLEI card. I have some
comments on the plots and a more general one on the procedure. I'll start
with the general ones..
It seems to me that the easiest way to get the isotope production would be
the RESNUCLEI card. This gives you directly the isotope production per
beam particle, independently on your
irradiation/decay times and on the subsequent simulation of radioactive
decay and photon production. Extraction of the cross section from photon
counting may become tricky if you have different branches that build up
the same nucleus.
If you need to compare directly with an experimental measurement with a
given irradiation time and after a given cooling time, you can again use
the RESNUCLEI with the associated DCYTIMES etc. This will give you the
activity for every isotope at a given cooling time taking into account the
build-up from the radioactive decay chain.
It would be much safer than using the mgdraw routine, where you had to
deal yourself with the irradiation/decay times.
Moreover, using the RESNUCLEI you could simulate (if needed) very thin
targets and bias the interaction probability through LAM-BIAS, to improve
efficiency and avoid target thickness effects. In mgdraw this becomes
difficult because you have to take weights into account.

About isomers: the present interactions models do not distinguish among
ground state and isomeric states (it would require spin/parity dependent
calculations in evaporation). A rough estimate (equal sharing among
states) of isomer production can be activated in the RADDECAY option. This
applies ONLY to the direct production through nuclear reactions, not to
the subsequent decay : if isomers are present in the radioactive decay
chain they, and their daughters, are correctly simulated.

Going to more specific points:

-- protons on Fe: you show a deficit at low energies: which target
thickness did you use? the energy loss may be important, and affect the
near-threshold behaviour. At 8 MeV, I get approx 10mb for Co-57 and approx
200mb for Co-56, that is consistent with literature. Please check your
-- protons on Copper: for the production of Zn65 you plot literature data
obtained from reactions on Cu-65, but the input you sent has natural
copper as material. The difference is important, at 15 MeV I get 85mb for
Cu65 and 26mb for natural copper. Please check what material did you
really use and compare to.
    For the production of Zn63, you show a deficit at low energies. However,
   the experimental data are for p on Cu63, not natural Cu, and again the
target thickness may play a role. At 10 Mev on 63-Cu I get 270mb of
Zr63, dropping to 200mb with natural copper, and going to 150mb with
natural copper .01mm thick.

-- In and isomers: see above: the reaction models produce In110, then the
decay module splits this in half ground, half isomer. Of course this is
not accurate, it is just a rough patch.

Hope this helps

> Dear Fluka users,
> I have some problems with the cross sections of production of some
> isotopes from
> the reaction of a natural metal + protons. What I am trying to do is very
> simple: I have a natural metal target and a proton beam, with different
> energy
> for each input file from 1 to 30 MeV. From the reaction of target and
> beam,
> several radioactive isotopes are produced. Counting the number of the
> photons of
> decay, I can discover how many isotopes of the same kind are produced.
> For example Fe + p produce, among others, Co56: counting how many photons
> at 846
> or 1238 keV (created with different percentages by the decay of Co56) are
> produced I can know how many Co56 are produced and so calculate the cross
> section of production. The problem is that if I compare the cross sections
> calculated using Fluka with this method and the cross sections of
> production of
> Co56 (or Co57 counting the photons at 122 keV) in literature, the
> agreement is
> not good, in particular at low proton energy.
> I have noticed that the same happens for Cd and Cu targets.
> In particular for the Cd target (thickness 0.1mm), I discovered that the
> cross
> sections of production of In110 in ground state are completely different
> compared to the cross sections in literature for proton energy lower than
> 30
> MeV: the cross sections obtained with Fluka are larger. The same happens
> with In
> 110 (metastable state), but this time the cross sections produced with
> Fluka are
> lower than those in literature. On the other hand, the cross sections of
> production of In 110 (ground + metastable state) are quite comparable with
> those
> in literature: the errors of the two separated isotopes combine to create
> something comparable with the literature.
> With Cu+p reactions, I went to look at the production of Zn63 and Zn65 (I
> used a
> 0.05mm thick target of copper). For Zn63 production the cross section
> becomes
> comparable with those in literature from 14 MeV, and for Zn65 the cross
> section
> is not comparable from around 12 to 20 MeV.
> The number of photons is counted using the mgdraw routine combined with
> Paw to
> visualise the data.
> Do I have some problems in the input file or is the approach wrong?
> Input file, the used routines and some graphs of the cross section
> comparison
> are attached.
> Thanks in advance
> Francesca Fiorini
> -------------------------------------------------
> This mail sent through IMP:

Paola Sala
INFN Milano
tel. Milano +39-0250317374
tel. CERN +41-227679148
Received on Wed Jul 15 2009 - 15:17:10 CEST

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