Dear Mitja,
I'm sorry, I cannot reproduce your problem
Please find attached a plot and a tab_lis file, obtained with an input
(also attached)
that has a few minor modifications with respect to yours:
- a larger detector and smaller beam divergency in order to increase
statistics. Together they give a factor 400 on normalization
- Added usrtrack in lead and target
- Added log usrtrack (not really needed)
- Separated collimator hole from vacuum to easily change configuration
As you see from the plot, I get a smooth spectrum in the detector, no
jumps.
You can also check directly in the _tab.lis file, that contains the
numbers to be plotted.
I do not know what could be the problem, maybe you could send one of the
.out files and the _tab.lis you get?
Regards
Paola
On Fri, 17 Apr 2020, Mitja Majerle wrote:
> Dear experts,
>
> updating this issue with this figure:
>
> The lower curve is produced with a minimalistic setup, lead cylindrical
> collimator, isotropic neutron source (gauss distribution, E0=15Mev,
> FWHM=15MeV) at one side, detector on another side (inp file in PS). The
> artefact at 20 MeV is clearly seen.
>
> The upper curve is the same situation, but instead of collimator the lead
> blocks are placed next to the axis from source to detector. What is the
> reason for this artefact ? Is the library below and above 20 MeV consistent ?
>
> Thank you,
>
> Mitja Majerle, NPI CAS
>
> PS -
>
> TITLE
> test
> GLOBAL 1. 1. DEPRBODY
> DEFAULTS NEW-DEFA
> BEAM -0.015 -0.168558 10000. 0.0 0.0 -1.NEUTRON
> BEAMPOS 0.0 0.0 -122.31 0.0 0.0
> GEOBEGIN COMBNAME
> 0 0
> * air around
> SPH blkbody1 0.0 0.0 0.0 10000.
> SPH void 0.0 0.0 0.0 1000.
> * 1 Li target
> RCC target 0.0 0.0 -122.3 0.0 0.0 0.4 3.5
> RCC ldout 0.0 0.3 -70. 0.0 0.0 70. 20.
> RCC ldin 0.0 0.3 -70. 0.0 0.0 70. 8.
> * 50 det CUP
> RCC detcup 0.0 0.0 75.4 0.0 0.0 5. 2.53
> END
> BLKBODY 5 +blkbody1 -void
> VOID 5 +void -ldout -detcup -target | +ldin
> TARGET 5 +target
> LEAD 5 +ldout -ldin
> DETCUP 5 +detcup
> END
> GEOEND
> ASSIGNMA BLCKHOLE BLKBODY
> ASSIGNMA VACUUM VOID
> ASSIGNMA VACUUM DETCUP
> ASSIGNMA LITHIUM TARGET
> ASSIGNMA LEAD LEAD
> MATERIAL 3. 0.534 LITHIUM
> MAT-PROP 40. LITHIUM
> MAT-PROP 10. LITHIUM DPA-ENER
> STERNHEI 3.1221 0.1304 1.6397 0.95136 2.4993 0.14LITHIUM
> MGNFIELD 20. 0.2 0.10 0.0 0.529 0.0
> USRTRACK 1. NEUTRON -25. DETCUP 100.54 400.detcup
> USRTRACK 0.10 0.0 7. &
> RANDOMIZ 1.0 0.
> START 3E+8 0.0
> STOP
>
>
>
> On 14.04.2020 21:23, Mitja Majerle wrote:
>
>> Dear FLUKA experts,
>>
>> I observed a strange artefact of the neutron spectrum when using lead in my
>> geometry:
>>
>> It occurs at 20 MeV, at the transition where multigroup transport takes
>> over. Below 20 MeV, there is 10% increase of the neutron flux, which is
>> unphysical. It is very pronounced for lead, barely visible if I change the
>> material to IRON, and dissapears if I replace material LEAD with VACUUM. I
>> am aware of different binning, what is on the Figure are FLAIR plots from
>> _tab.lis files. I am trying to break down the geometry and source to
>> something simpler to demonstrate here, but it takes time and maybe somebody
>> has already seen something similar and can help ?
>>
>> Thank you,
>>
>> Mitja
>>
>>
>
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Received on Sun Apr 26 2020 - 14:16:10 CEST