Re: [fluka-discuss]: Re: Problem with transporting neutrons

From: Mina Nozar <nozarm_at_triumf.ca>
Date: Tue, 24 Feb 2015 14:49:05 -0800

Hello Nkanyiso,

I am sending this to the forum as well since others might be able to
offer more help.

I have few questions and suggestions:

What exactly is your reaction? Is it protons on Be or protons on Li?
The reaction you included in your first message was Li(p,n)Be which
means protons on Li. Do you have protons on Be?

Which figure in your plot should I be looking at? Fig. (b)? What does
Cal. Be mean? Is this results from your FLUKA imulated simulations?


Why did you change number of bins in omega to 10 from 1? It seems to me
your are interested in single differential fluence (i.e. fluence as a
function of energy) so why the 10 bins in omega?

In the new example, you have reduced the beam energy from 200 MeV to 66
MeV, and the target from a 1x1x1 cm cube to a sphere with a radius of
2.5 cm. Your 0 deg detector is now around 770 cm away from the target
when in the first example, it was around 10 cm away.

Your beam is annular and less than 1 cm in diameter. Your second
detector is off axis by 212 cm in X. In the previous example, your
off-axis detector was off axis by ony 3 cm. When you look at beam part
and/or proton distribution, what do you see?

Note that in your USRBIN cards, you don't need to go from -900 to 900 cm
in Z. And X and Y don't have any meaning when What(1) is set to R-Phi_Z.


Best wishes,
Mina



On 15-02-24 07:46 AM, NKANYISO ROBERT Mantengu wrote:
> Hi mina I hope you are doing good.
>
> I'm sorry for asking you in person, but but i have a problem now when
> I locate the detector at 7.7m.
> I only get the peak at low-energies, I don't know if the problem is
> with thickness but i have the measured spectra for 10mm Be, with 66MeV
> proton beam
>
> Here I have attached the input file together with the picture of the
> measured spectra for Be
>
> Regards
> N.R Mantengu
>
> On Fri, Feb 20, 2015 at 6:30 PM, NKANYISO ROBERT Mantengu
> <3477531_at_myuwc.ac.za <mailto:3477531_at_myuwc.ac.za>> wrote:
>
> Thank you very much Mina
>
> Regards
> Nkanyiso
>
> On Fri, Feb 20, 2015 at 6:21 PM, <nozarm_at_triumf.ca
> <mailto:nozarm_at_triumf.ca>> wrote:
>
> Hello Nkanyiso,
>
> I made some changes to your input file and ran it.
> Changes:
>
> 0) Your reactions is Li(p,n)Be. So Protons on Li. You had Be
> for the
> material of your target. I changed it to Li.
>
> 1) Annular beam (R_in = 0.7 cm, R_out = 1.2 cm) to (R_in = 0,
> R_out = 0.5)
> I did this to get more statistics since your target is a 1x1x1
> cm cube.
> Is this really the setup you did your measurement? i.e.
> annular beam with
> R_in = 0.7 cm, R_out = 1.2 cm on a 1x1x1 cm cube?
>
> 2) Changed number of bins for omega in the USRBDX cards from
> 10 to 1.
>
> 3) Added two USRBIN estimators to looks at Beam particle and
> Neutron
> spacial distributions. (My recommendation is "ALWAYS look at
> where your
> beam distribution to make sure you have set up your beam
> correctly").
>
> 4) Added two USRTRACK estimators to look at the Neutron fluence
> distributions in the two detectors.
>
> 5) Took out the unnecessary EMF card.
>
> 6) Added a flair project to look at a few plots of the produced
> distributions.
>
>
> I ran the project for 150M primaries to get reasonable
> statistics. I am
> looking at the distributions from home so can't quite compare
> with the
> measurements. Take a look and see for yourself and report back.
>
> Best wishes,
> Mina
>
>
> > Sorry I have captured the wrong picture for measured spectrum
> >
> > Here in the right one
> >
> > Regards
> > N.R Mantengu
> >
> > On Wed, Feb 18, 2015 at 6:05 PM, NKANYISO ROBERT Mantengu <
> > 3477531_at_myuwc.ac.za <mailto:3477531_at_myuwc.ac.za>> wrote:
> >
> >> Dear Fluka experts,
> >> Can someone help me out here I'm transporting neutron
> fluence using
> >> USRBDX
> >> card, but the spectra that I get doesn't seam to be
> consistent with the
> >> measured one.
> >>
> >> Here is the input file and the spectra
> >> any comment or advice will be appreciated.
> >>
> >> #Sorry for the units in the calculated spectra, but its
> Energy in GeV on
> >> X
> >> axis and its fluence in part/GeV/cm^2 on Y axis
> >>
> >> Regards
> >> N.R Mantengu
> >>
> >
>
>
>





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Received on Wed Feb 25 2015 - 01:47:16 CET

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