Re: [fluka-discuss]: Interactions at surface between air and air

From: Vittorio Boccone <dr.vittorio.boccone_at_ieee.org>
Date: Wed, 30 Apr 2014 23:13:00 +0200

Dear Kilian,


> When assigning the material of the
> region to air, it should be as if there is no region at all (because
> the enviroment and the region consist of the same material).
>
You assign it to air. Was it vacuum before or just the geometrical
representation of the phantom was different?
Which sizes are we talking about (meters, cm, mm or um?)

However, the depthdose-curve (for <1E05 primaries) in the water-phantom is
> significantly different to the depthdose-curve, when there is no
> region.

What do you meas about significantly different? Did you check the
statistical error of the simulation?


> However this effect gets lost, when using >1E07 primaries.
>
This is a sign that you are very much dominated by the statistical error
with less then 10 Millions of particles. This is realistic because the dose
in air requires typically a lot of statistics or larger averaging
bins/regions.

Your input file would be probably useful to check which are your physics
setting and the scoring you are performing.

Best,
V.


On Wed, Apr 30, 2014 at 10:05 PM, Kilian Baumann
<baumann.kilian_at_gmail.com>wrote:

> Dear Fluka-experts!
>
> I have discovered a (perhaps) strange result, when analysing the
> depthdose-curve and fluence, when irradiating a waterphantom with a
> region in front of it. My whole setup consists of the beam source (80
> MeV carbon-ions), a water phantom and a region between waterphantmom
> and source. The enviroment is air. When assigning the material of the
> region to air, it should be as if there is no region at all (because
> the enviroment and the region consist of the same material). However,
> the depthdose-curve (for <1E05 primaries) in the waterphantom is
> significantly different to the depthdose-curve, when there is no
> region. However this effect gets lost, when using >1E07 primaries.
> Furthermore I analysed the fluence at the surface of the region, so to
> say at the surface between air and air and indepent on the amount of
> primaries one can see a change in fluence at the surface.
> My question now is, what FLUKA is exacly calculating near this
> surface/region (perhaps some artefacts with single-/multi-scattering)
> and if any effects are negiglibly if using a sufficient amount of
> primaries.
> Thanking you in advance!
> Best regards,
> Kilian
>
>
Received on Thu May 01 2014 - 00:12:47 CEST