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

From: NKANYISO ROBERT Mantengu <3477531_at_myuwc.ac.za>
Date: Wed, 25 Feb 2015 10:03:00 +0200

I've tried to update and change some things like number of beens in omega
from 10 back to 1 and target thickness from 5 cm to 1cm because I suspected
it could be the stopping length, but still I get the same spectra with a
peak at low energies.

I'm lost, please help.

Regards
N.R Mantengu.

On Wed, Feb 25, 2015 at 9:04 AM, NKANYISO ROBERT Mantengu <
3477531_at_myuwc.ac.za> wrote:

> Hi Mina
>
> Last time my reaction was Li(p,n)Be but now its proton on Be.
> You should be looking at Fig. (b)
> Cal. Be mean calculated Be fluence spectrum.
> Yes, the calculated result from FLUKA simulation.
>
> I had a misunderstanding, thats why I made a mistake of changing the
> number of bins in omega from 1 to 10.
> Yeah the Be measured spectra was done for 66 MeV then I was forced to
> reduce the energy, and the detectors were placed 7.7m away from the target
> at 0 and 16 degrees.
> When I try to plot to see the distribution I get an error
>
> Regards
> N.R Mantengu
>
>
> On Wed, Feb 25, 2015 at 12:49 AM, Mina Nozar <nozarm_at_triumf.ca> wrote:
>
>> 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> wrote:
>>
>>> Thank you very much Mina
>>>
>>> Regards
>>> Nkanyiso
>>>
>>> On Fri, Feb 20, 2015 at 6:21 PM, <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> 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 - 10:45:05 CET

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