RE: [fluka-discuss]: (без темы)

From: Anton Lechner <>
Date: Thu, 13 Jul 2017 15:22:57 +0000


I first have a principal remark to your geometry: your gold layer has a thickness of 4nm which is much too thin for condensed history Monte Carlo codes. It is generally recommended that region dimensions in FLUKA simulations should not be smaller than ~1um.

Apart from that, LAM-BIAS would still be the right biasing approach, however the multiplication factor on WHAT(2) is still much too large in your case (0.03). Considering that the cross section for 197Au(gamma,n)196Au is of the order of 500mb at the GDR peak, this means that the mean free path is around 34 cm. For a layer thickness of d=4nm, this implies that the interaction probability (d/lambda) is only about 1E-8. Hence a multiplication factor of 0.03 will not improve much the situation since the biased interaction length is still ~1cm (in addition, you have to consider that your gold foil covers only a small solid angle interval at 90 deg from the beam direction, i.e. only a fraction of events will give rise to photo-nuclear interactions in the gold foil even with LAM-BIAS: if your simulation problem permits, one could maybe think of using a model which is azimuthally symmetric?).

Secondly, EMF-CUT is not efficient in your case to gain CPU time (just a minor remark: you put your cuts at 9 MeV so you already cut into the tail of the GDR cross section, anyway this is probably not so important since the peak for Au is around 13-14MeV).

Cheers, Anton

From: [] on behalf of kabytayeva []
Sent: 12 July 2017 15:24
To: Fluka Discuss
Subject: [fluka-discuss]: (без темы)

Hello everybody!
I need your help again
I interested in the production of 196Au and 198Au, but thickness of the
target 197Au is very small and I need more CPU time.I tried to add
EMT-CUT and LAM-BIAS, but it is not help me...Do you have any idea?

Many thanks!

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Received on Thu Jul 13 2017 - 18:30:18 CEST

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