Physics list for shielding <20 MeV Neutron

Dear all,
I am working with a 18.5 MeV neutron source with a concrete bunker as shield.
I am facing a problem,
Without the HP model, FTFT_BERT and QGSP_BERT, QBBC etc are working fine.

But when I take FTFT_BERT_HP, QGSP_BER_HP, the High Precision models, the bunker can’t shield all the beams. Figure below.

Should I ignore the transmitted neutrons? And why HP models are unable to shield these? I fear there is some problem here. Please suggest which physics list I should use here?

Hello Arnab913,

I’m pretty sure, that HP Physics Lists are working well for neutrons. Also, a MeV neutrons can penetrate a little inside concrete walls, but you know that.

Please give us more details, e.g. run3.mac file, materials of the geometry, dimensions. I can try to reproduce this effect for you.

I assume, that geometry doesn’t have any overlapping volumes.

Regards,
Marcin

1 Like

There is a “Shielding” list designed exactly for this case

Dear MKasztelan.
thanks for the reply.
The bunker is a 101010 cubic meter hollow box where inner wall thickness is 2.44 m all around. In the center, a neutron particle gun is set and bombarding along z direction. I am using varoius concrete mixtures , you can try G4_concrete.
The run3.mac file is here.Processing: run3.mac…

# ########################################
#
/score/create/boxMesh boxMesh_2a
#
#/score/mesh/boxSize 5.5 5.5 2.44 m
/score/mesh/boxSize 10. 10. 10. m
#/score/mesh/boxSize 0. 0. 1. m
/score/mesh/translate/xyz 0. 0. 0. m
#/score/mesh/translate/xyz 0. 0. -7.56 m
/score/mesh/nBin 1 1 10000
#
#/score/quantity/nOfStep nOfStepGamma
#/score/quantity/energyDeposit eDep
/score/quantity/doseDeposit dose
#/score/filter/particle gammaFilter gamma
#
/score/close
#
########################################


########################################

########################################
#
/score/list
#
/vis/disable
/gun/particle neutron
/gun/energy 18.5 MeV
/run/beamOn 100000
/vis/enable
#
########################################
#
#/analysis/setFileName neutron.root
#/analysis/h1/set 1 100 0.  1. mm	#edep profile
#

#/score/drawProjection boxMesh_2a dose
#/score/drawProjection boxMesh_2a eDep
#
########################################
# Dump scores to a file

/score/dumpQuantityToFile boxMesh_2a dose dose.txt
#/score/dumpQuantityToFile boxMesh_2a eDep edep.txt
#
########################################
#/score/drawColumn boxMesh_2a dose 1 0

Thanks again.

Dear bloer,
I also have tried shielding, but this also results the same.