Re: cross sections of production: comparison with literature

From: <>
Date: Wed, 15 Jul 2009 17:38:20 +0200

Thanks Paola for the answer and the advises.
I have chosen the way of mgdraw, because, changing the geometry in the input
file, that was the easiest way to obtain a direct comparison with the data of my
experiment (where I go to count the produced gamma of decay using a HPGe
detector). Moreover with this method I can check the evolution in time of the
activity: asking mgdraw to write the atack quantity I can changing the cooling
time without repeating every time the simulation.

With regard to photons, I take into consideration only the photons the which
production is only due by a single isotopic species. So, for example, the 846
keV photons, considered to calculate the cross sections of production of 56Co
(produced by natFe+p), are exclusively generated by 56Co. This is valid for
every considered gamma. So if this is true I shouldnÂ’t have problems of
building-up. On the other hand, as you also said, I cannot use thick targets,
above all at low energy (the used natural Fe target was thick 0.1mm).

With regard to the isomers, I have activated their production using w(2)>0 in
the RADDECAY card, and both 110In(g) and 110In(m) are produced directly by
natCd+p. But if you say that their production is not accurate, I will ovoid
considering them.

Finally, with regard to the comments about the graphs of Cu+p-->6xZn+n,
unfortunately the y-axis labels were incorrect: the correct labels are Cu+p--
>63Zn+n and Cu+p-->65Zn+n, sorry! So the data in literature and the those
obtained using Fluka can be compared because they treat the same reaction. This
is proved also by the fact that your calculations with natural Cu are well
comparable with the data in literature and with my simulations.

Scrive Paola Sala <>:

> 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
> target.
> -- 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
> Paola
> > 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

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