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
>
>
__________________________________________________________________________
You can manage unsubscription from this mailing list at
https://www.fluka.org/fluka.php?id=acc_info
Received on Fri Apr 17 2020 - 17:08:10 CEST