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From: Alberto Fasso <fasso_at_mail.cern.ch>

Date: Thu, 20 Feb 2014 15:24:17 +0100

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 - 16:22:22 CET

Date: Thu, 20 Feb 2014 15:24:17 +0100

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:

Received on Thu Feb 20 2014 - 16:22:22 CET

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