RE: [fluka-discuss]: Neutron cross section

From: Jonathan Derrien <jderrien_at_ulb.ac.be>
Date: Thu, 20 Feb 2014 16:32:25 +0100

Dear Alberto,
This is a part of one of the output file (.out):
1 Cross sections for media 1 (Residual nuclei informations available) GROUP SIGT SIGST PNUP PNABS GAMGEN NU*FIS EDEP PNEL PXN PFISS PNGAM PNP PNA barn barn GeV/col 1 2.118E+00 2.806E+00 0.000 1.325 1.512 0.000 0.001 0.564 5.356E-01 0.0000 0.0002 0.0080 0.0066 2 2.123E+00 2.832E+00 0.000 1.334 1.514 0.000 0.001 0.575 5.463E-01 0.0000 0.0003 0.0086 0.0072 3 2.146E+00 2.875E+00 0.000 1.340 1.498 0.000 0.001 0.581 5.527E-01 0.0000 0.0003 0.0092 0.0077 . . .
As you can see, there are PNP and PNA. For activation, you talk about a separate table: what kind of table is it? How is it computed? How Fluka can solve Bateman equation with this table? Normally, Bateman equation needs some information to be solved: fluence, cross-section etc (or other variables link to these last one). I really want to know how the activation works with FLUKA.
Thank you,
Jonathan
--
> Date: Thu, 20 Feb 2014 15:24:17 +0100
> From: fasso_at_mail.cern.ch
> To: fluka-discuss_at_fluka.org
> CC: jderrien_at_ulb.ac.be; dr.vittorio.boccone_at_ieee.org
> Subject: RE: [fluka-discuss]: Neutron cross section
> 
> Hi Jonathan,
> 
> reading your first email, I wasn't sure where you had found PNP and PNA.
> Now that you say you refer to the cross sections printed by LOW-NEUT, I 
> can assure you that neither is there with such names. The only ones that 
> more or less look similar are the following (I am quoting from the Manual,
> Chapter 9):
> 
> PNUP   = upscatter probability (can be different from zero only if
>           there are several thermal groups)
> PNABS  = probability of Non-ABSorption (= scattering).
>           It is = SIGST/SIGT, and can sometimes be > 1 because of
>           (n,xn) reactions
> PNEL, PXN, PFISS, PNGAM = partial cross sections, expressed as
>           probabilities (i.e. ratios to SIGT). In the order:
>           non-elastic, (n,xn), fission, (n,gamma)
> 
> Group cross sections are mainly for neutron transport, not for activation.
> The only exceptions are PNGAM and the 14-N(n,p)14-C cross section. The 
> situation is different for the few cases where pointwise cross sections
> can be used (6-Li and 10-B(n,alpha)7-Li). In FLUKA, activation by 
> low-energy neutrons is obtained by a separate table of residual
> nuclei, where the values are group dependent and uncorrelated with the 
> actual sampled reaction.
> 
> Alberto
> 
> On Thu, 20 Feb 2014, Jonathan Derrien wrote:
> 
> > Hello Vittorio,
> > 
> > Thank you to trying to answer my question. Well, for neutron with energies
> > below 20 MeV, cross-section libraries are used. These cross-sections can be
> > seen by using the command LOW-NEUT.  Have you any idea about how compute the
> > activation cross-section thanks to the data given by LOW-NEUT?
> > 
> > Best,
> > 
> > Jonathan
> > --
> > [mywebsite.ulb.ac.be&x=46&y=10&]
> > 
> > ____________________________________________________________________________
> > Date: Thu, 20 Feb 2014 14:26:53 +0100
> > Subject: Re: [fluka-discuss]: Neutron cross section
> > From: dr.vittorio.boccone_at_ieee.org
> > To: jderrien_at_ulb.ac.be
> > CC: fluka-discuss_at_fluka.org
> > 
> > Dear Jonathan, 
> > What do you exactly mean with "data used by Fluka,  I'm not sure if I'm
> > mislead by the name but I had some memories that those could be the
> > probabilities of emission of a neutron and a proton (Pnp) and the one for
> > the emission of a neutron and an alpha (Pna). 
> > 
> > best, 
> > V.
> > 
> > 
> > On Thu, Feb 13, 2014 at 10:55 AM, Jonathan Derrien <jderrien_at_ulb.ac.be>
> > wrote:
> >       Hello dear Fluka Users,
> > I'm using the data used by Fluka for the low neutron and  I found
> > among the cross section and different probabilities two probabilities:
> > PNP and PNA. I do not see what it is, so what is their meaning?
> > Moreover, does anyone know how from these data to determine the
> > activation cross section? 
> > Sincerely, 
> > 
> > Jonathan Derrien
> > 
> > --
> > [mywebsite.ulb.ac.be&x=46&y=10&]
> > 
> > 
> > 
> >
 		 	   		  
Received on Thu Feb 20 2014 - 18:44:14 CET

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