Re: [fluka-discuss]: fluka simulation

From: Anna Ferrari <a.ferrari_at_hzdr.de>
Date: Thu, 16 Jul 2015 17:39:06 +0200

Dear user,

first, a preliminary comment. What do you mean by "hits chemically more stable
cooled tungsten target"? What has chemistry to do with your problem?

Let's come to the answers.
If we understand you correctly, you expected to get more 6-He from a 23.5 MeV
electron beam than from a 22 MeV electron beam. Why? What yield do you get in
the two cases? With which statistical error? What increase do you expect?
You have to consider that the 6-He yield is due to bremsstrahlung photons with
energy in the region of the Giant Resonance (in your case between 10 MeV and
the energy of the beam). The number of those photons cannot change very much
if the electron energy is increased by 1.5 MeV! Probably the yield you get is
about the same, WITHIN THE STATISTICAL ERROR (you did not provide it!).

Apart from that, there are a few not recommended things in your input file,
1) Why do you ask for single scattering? In your case single scattering will
only slow down considerably your calculation, without any improvement in the
results.
2) Why do you set an electron transport cutoff of 100 keV and a photon cutoff
of 20 keV? The threshold for the 7-Li(gamma,p)6-He reaction is 10 MeV.
Transporting photons, and especially electrons, below that energy
is just a waste of CPU time. We suggest that you set those thresholds at 10
MeV, and avoid leading particle biasing (EMF-BIAS) which can be useful for
shielding calculations, but is certainly not the good choice here.
3) The definition of region VOID is unnecessarily complicated:
VOID 5 +void -targstar -targend
| +void -target
| +void +converte
Body targstar is contained within body targend, therefore you need to subtract
only targend.
4) Less important: you should not enter the mass number of FLUORINE and
TUNGSTEN (18.998, 183.84).
FLUKA has its own table of mass numbers and does not need them. By the way,
TUNGSTEN is also one of the pre-defined materials and does not need to be
defined.

Hope it helps,
Anna

Am Tue, 14 Jul 2015 22:38:19 +0300 schrieb teterev <teterev_at_jinr.ru>:
> Hello!
> I really need your help! At the moment, I want to calculate the yield of
>helium-6 in the 7Li(g, p) reaction using electron bremsstrahlung. The beam
>of 22 MeV electrons hits chemically more stable cooled tungsten target . The
>thickness of the target 3.2 mm. Vessel filled by the irradiated material was
>disposed along the axis of the bremsstrahlung radiation. Lithium fluoride,
>with a density of 1 g / cm3 was tested as target material. But I have such a
>problem in fluka simulation, which is connected with the increase of electron
>energy to 23.5 MeV yield of helium-6 is not increased, although it should
>be otherwise. I ask you to look at the fluka code, because maybe I made a
>mistake.
>
> Thanks in advance !!!

~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~
Dr. Anna Ferrari
Institute of Radiation Physics
Helmholtz-Zentrum Dresden-Rossendorf e.V.
Tel. +49 351 260 2872
a.ferrari_at_hzdr.de
http://www.hzdr.de

Vorstand: Prof. Dr. Dr. h. c. Roland Sauerbrey, Prof. Dr. Dr. h. c. Peter
Joehnk
Vereinsregister: VR 1693 beim Amtsgericht Dresden

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Received on Thu Jul 16 2015 - 18:49:59 CEST

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