Dear Francesca
the artifact is indeed a threshold problem. Using the PRECISION default,
the transport threshold for electrons is set at 100 keV, that corresponds
to a range of 14 cm in air, much more than the scoring and geometry
dimensions in your problem
In the case without disk:
-beta decay electrons generated below 100 keV will stop at the production
point
- the other will be transported with a first "step" that is automatically
calculated by the code, and depends on both energy and distance to next
geometry boundaries (the rest of your geometry)
- at the end of this step, all electrons that lost enough energy to go
below 100 keV will be stopped and their energy deposited "on spot". This
is the anomalous rise that you see at about 1cm from source.
So: to get reasonable results in a gaseous medium..keep thresholds low,
compatible with your scoring and your geometry.
If you wish to check, try setting EMFCUT with a kinetic threshold of 10
KeV, the artifact disappears.
Hope this helps
Paola
> Hi Paola,
> thank you for your answer.
> In attach You can find the three imput files mentioned in the first
> message.
> When I say "there is a rise in the loss of energy" as you can see on the
> right of the image "Loss_of_energy_along_z_axis.png
> <http://www.fluka.org/web_archive/earchive/new-fluka-discuss/att-10626/Loss_of_energy_along_z_axis.png>"
> (case without disc), i'm expeting a 1/r^2 trend because i've only
> interations with air, while what I actually get is a rise in a point that
> is after the edges of the disc (that is centered in z=2.5 cm with radius=1
> cm). What do you think about it?
> P.S. I've not choose any threshold for the transport.
> Cordially,
> Francesca
>
> 2017-08-28 8:35 GMT+01:00 paola sala <paola.sala_at_cern.ch>:
>
>> Dear Francesca,
>>
>> when you say "there is a rise in the loss of energy" you mean the rise
>> at
>> the edges of the disk? Could you please check what are the transport
>> thresholds for electrons and photons in the materials/regions of the
>> disk
>> and around?
>>
>> (or send the input file)
>>
>> Thank you
>>
>> Paola
>>
>>
>>
>> On 08/24/2017 06:02 PM, francesca falorsi wrote:
>>
>>> Dears Fluka's Expert,
>>> I 've a question for You.
>>> I'm simulating the decay of a point like source of Cs-137 with the
>>> geometric configuration that you can find in attach.
>>> I'm doing two type of simulations: the first one putting the point like
>>> source into a PMMA disc and the second one removing the disc.
>>>
>>> I'm having some problems with interpreting what i get by the usrbin
>>> card: in the event the disc is not present there is a rise in the loss
>>> of
>>> energy.
>>> I put in attach the screens of the results, on the left there is the
>>> case
>>> in which the disc is present and on the right the one in which is not
>>> present.
>>> I tried to do another simulation in which I put only the source in the
>>> space, obtaining the same result; You can find these others results in
>>> attach (the files in which is present "other simulation" in the name).
>>> Thanking you for your attention I'll wait for your opinions.
>>> Francesca
>>>
>>
>>
>
Paola Sala
INFN Milano
tel. Milano +39-0250317374
tel. CERN +41-227679148
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Received on Tue Sep 12 2017 - 12:42:53 CEST
