Re: secondary neutrons missing from usrrnc.f

From: Shirley Li <shirleyli.phys_at_gmail.com>
Date: Sun, 24 Feb 2013 15:32:22 -0500

Hi Vittorio,

I looked at Chapter 10 of the manual, but I'm still a little confused about
the concept of the multi-group treatment. From my understanding, the
production of secondary neutrons via (n, xn) are totally independent of ANY
other secondaries including gamma, alpha, proton, residual nucleus etc
(except for special case like H(n, g)D). Is that correct?

Thank you!
Shirley

On Sun, Feb 24, 2013 at 9:03 AM, Vittorio Boccone
<Vittorio.Boccone_at_cern.ch>wrote:

> Hi Shirley,
> it depends… gamma generation, secondary neutrons via (n,xn)
> reactions, fission neutrons generation are all handled using a
> group-dependent cross sections.
>
> The recoil protons and the ones from n-p reactions are handled using the
> elastic scattering kinematic.
> This is also the case for light fragments (alpha, He3) in the case of 6Li
> and 10B (but only if you activate explicitly)
>
> Please give a look at the chapter 10 of the the manual for more details.
>
> Best
> Vittorio
>
> On 19 Feb 2013, at 22:54, Shirley Li <shirleyli.phys_at_gmail.com> wrote:
>
> Dear Vasilis,
>
> Sorry to bother you. I'm still trying to understand secondaries from low
> energy neutron reaction.
>
> When you said FLUKA samples totally uncorrelated residuals with the
> event, does that mean that the residual nucleus from a event is calculated
> independently from the other secondaries (n, p or alpha particles)? So,
> it's meaningless to say I got certain residuals from certain reaction?
>
> Thanks!
> Shirley
>
> On Mon, Sep 3, 2012 at 8:31 AM, Vasilis Vlachoudis <
> Vasilis.Vlachoudis_at_cern.ch> wrote:
>
>> Dear Shirley,
>>
>> unfortunately this is not a bug but a feature. Due to the group-wise
>> treatment of the low-energy neutrons the meaning of a single interaction is
>> almost lost, with the direct consequence on the information of the residual
>> nuclei. Therefore FLUKA (and only for the low-energy neutrons with
>> group-wise xs) is sampling totally uncorrelated the residual nucleus with
>> the event and the deposited energy (only if a residual scoring is
>> requested).
>>
>> Regards
>> Vasilis
>>
>>
>> ________________________________________
>> From: owner-fluka-discuss_at_mi.infn.it [owner-fluka-discuss_at_mi.infn.it] on
>> behalf of Shirley Li [shirleyli.phys_at_gmail.com]
>> Sent: 31 August 2012 22:17
>> To: fluka-discuss_at_fluka.org
>> Subject: secondary neutrons missing from usrrnc.f
>>
>> Dear fluka users,
>>
>> I'm trying to simulate neutron yield from a muon beam passing through
>> water. I modified mgdraw.f and count neutron yield from every
>> interaction. The number is consistent with published results to about
>> 10%. Then, I tried to compare neutron yield to residual nuclei, i.e.,
>> every time some neutrons get generated, there should be residual
>> nucleus produced at the same time. So I modified usrrnc to look at the
>> reactions/neutron yield. However, some low energy neutron interactions
>> look different in the outputs from mgdraw and usrrnc. In both
>> subroutines, I look at interaction by
>>
>> WRITE ( unit, *) NCASE, JTRACK, ETRACK
>>
>> do ip = 1, NP
>> WRITE ( unit, *) ip, KPART(ip), TKI(ip)
>> continue
>>
>> do ipheav = 1, NPHEAV
>> WRITE ( unit, *) ipheav, -KHEAVY(ipheav), TKHEAV(ipheav)
>> continue
>>
>> There are a lot of reactions reading from mgdraw.f output is a parent
>> low energy neutron generates one neutron. However, this reaction
>> seeing from usrrnc output is one parent neutron generates a 16O (since
>> it's in water) with NO child neutron. This also happens to some
>> similar reactions where basically it's low energy neutron bouncing off
>> nuclei and losing energy with no other real secondaries. However, the
>> neutron doesn't appear in usrrnc.f secondary but it does appear in
>> mgdraw.f secondary. Does anyone know why this is?
>>
>> Thanks!
>>
>> Shirley Li
>>
>>
>
>
Received on Sun Feb 24 2013 - 23:22:26 CET