Another question about neutron counting

Dear Francesco and all,
First, thanks Francesco for the kindly help. But I still have some questions to consult you.

1) If I choose "fluence" with "neutron" in the USRBDX card, the simulated emergent neutron fluence (I) is larger than the incident
one (I0) when polyethylene is 0.5cm and the result is not the same as that of the experimental one. I really don't know how to
calculate the neutron macro cross-section for 2.45MeV neutron using the equation I=I0*e-^(Ķē*d) for 0.5cm polyethylene.

2) If I choose "fluence" with "beampart" for 2.45MeV neutron, the emergent neutron beampart is lower than the incident one and the
result is lower than that of the experimental one.I am a layman in this field, I don't quite understand what the first generation
particles' meaning is when using BEAMPART. Could you please explain it easy to understand ? Do you mean that the nuclear elastic and
low energy neutron elastic scattering is not considered to increase the generation number when using BEAMPART. Am I right? Thank you !
3) By the way, it is odd, only when choosing "current" with "neutron" in the USRBDX card, the simulated result is nearly the same as
that of the experimental one when using He3 proporational counter tube for 0.5cm to 3.0cm thickness polyethylene, I don't know why ?

Thanks in advanced and any help will be appreciated !

Regards

> Date: Mon, 14 Nov 2011 18:39:18 +0100
> From: Francesco.Cerutti_at_cern.ch
> To: lzfneu_at_live.com
> CC: fluka-discuss_at_fluka.org; giuseppe.battistoni_at_mi.infn.it
> Subject: Re: Question about neutron counting
>
>
> Hallo
>
> I would say that the relevant quantity, physically meaningful, is - as
> almost always (with the respective particle species) - 2) "fluence" with
> "neutron".
>
> BEAMPART refers to first generation (LTRACK=1) particles. Any discrete
> event (say interaction, apart from delta/Moller/Bhabha and nuclear elastic
> scattering - but note that for low energy neutrons elastic scattering is
> not disentangled as an independent interaction type - ) increases the
> generation number.
>
> Best regards
>
> Francesco
>
> **************************************************
> Francesco Cerutti
> CERN-EN/STI
> CH-1211 Geneva 23
> Switzerland
> tel. ++41 22 7678962
> fax ++41 22 7668854
>
> On Sat, 12 Nov 2011, lzfneu wrote:
>
> >
> > Dear all,
> > I want to calculate the theoretical transmission value (I/I0) of polyethylene for 2.45MeV neutron which range from 0.5cm to 3.0cm
> > thickness and compared with the experimental one. The counting experiment is He3 proportional counting tube. I am confused that
> > which one I should choose in the USRBDX card to do the simulation:
> > 1) "fluence" with "beampart";2) "fluence" with "neutron";or 3) "current" with "beampart";4) "current" with "neutron";
> > I am also confused that what the difference is between the "beampart" and "neutron" in the USRBDX card when neutron is scored, thank
> > you !
> > Thanks in advance and any help will be appreciated !
> > RegardsZ.F.Lee
> >
> >
> >
>
Received on Wed Nov 16 2011 - 15:32:51 CET