Re: Are different isotopes of the same element share the same neutron cross section data in FLUKA/FLAIR?

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Date: Thu, 7 Apr 2011 09:39:39 +0800 (CST)

Dear Ferrari,

To speak more specifically,I want to simulate a neutron source coming into
a region stuffed respectively by Gd-155 and Gd-157.I want to see the photon
deposition by energy.As these two isotopes have different neutron cross
sections,the results should be different.I have used the LOW-MAT card,only
to find that the library contains cross-sections for the natural gadolinium,
at two different temperatures,but not for gadolinium isotopes, while
cross-sections for isotopes of Hydrogen and Lithium,for example,are contained.
I'm not sure whether the cross-sections for the natural gadolinium contained
in the library are derived from all the isotopes of gadolinium,according to
their natural storage.If so,can I extract them?
So how can I associate the isotopes of gadolininium (that I create in MATERIAL card)
with the neutron cross sections of the GD isotopes respectively?

Best regrads,


Hallo Danny,

you can immediatly understand your result if you look at the manual
chapter that illustrates the FLUKA neutron cross section libraries for low
energy neutrons (chapter 10.4).
In the section you will find the list of materials for which
cross sections are available in the 260 neutron group library:
there you can read that the library contains cross-sections only for the
natural gadolinium, at two different temperatures.

I add, in case you need, that you can use the LOW-MAT card to associate
low-energy neutron cross sections to the FLUKA materials. If you don't use
this card (as in your case I suppose) the correspondence is by name and in
case of ambiguity -the same material at different temperatures for
example-the first material in the list is assumed. You used, therefore,
the cross section on natural gadolinium at 296 K.



> Dear all,
> I want to simulate the following reaction;
> n + Gd -> Gd(*) ...(1)
> Gd(*)-> Gd +garma ...(2)
> If I assign different mass number to Gd in reaction (1),that is to say
> isotopes of Gd,there will be isotopes of Gd(*) coming out,which leads to
> different energy distributions of garma in reaction(2).
> And when I assign different mass number to Gd and I use USRTRACK card to
> see the energy distribution of garma, the values of garma energy peak ar=
> exactly the same.So I wonder if Gd with mass number 155 and 157,for
> example,share the same neutron cross section,in the circumstance of a
> constant neutron energy.
> Yours,
> Danny
Received on Thu Apr 07 2011 - 15:39:42 CEST

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