Re: Bug in FLUKA or error in the setup?

From: Mina Nozar <nozarm_at_triumf.ca>
Date: Wed, 21 Aug 2013 19:19:22 -0700

2013 04:19:21 +0200 (CEST)
Sender: owner-fluka-discuss_at_smtp2.mi.infn.it

Hello everyone,

A big thanks to Alessio. We were able to nail down the issue earlier today.


The problem was from my end.

I was using expressions and parameters when defining the planes
dividing up the regions into subregions in flair, parameters like the
beam dump width, height, length, front face of the beam dump, beam y and
z positions, front face of the beam dump, etc. This time, when I
changed the parameter values to the ones I got from the engineer working
on the beam dump design, I only modified the main/master input file.
The cloned files were seeing the old parameters, and therefore, the
geometry for the cloned files was different (with lots of errors such as
BS04, BS08, BS12, and BS16 not even being defined - thus not seeing any
deposited energy in them).

I was under the impression that when the input files were copied, every
thing was copied from the master file. I wasn't aware that the
parameter values were not. So I should have either re-created the
cloned runs or changed the parameter values by hand (former is more
error-proof). This was the first time I had ran into this issue since
the parameters in the last projects I have worked on did not change
during the course of the analysis. The beam dump is under design so the
parameters did change and might change again.

So you can say the problem was literally right in front of my face
whenever I was setting off a test run but never bothered to look at the
parameters set for the cloned (and the test runs), thinking the values
were the ones set in the master input file.


Anyhow, a very tired but happy Mina. It is a good day when nagging
problems are solved.
And thanks again to Alessio.

Cheers,
Mina


On 13-08-15 12:19 PM, Mina Nozar wrote:
> Hello everyone,
>
> There is something happening in my setup that just doesn't make sense
> and I have tried different things in the last three days, trying to find
> out whether the mistake is from my part.
>
> I have 75 MeV electron beam 4x4 cm square incident on a Beam Dump
> composed of Al with some cooling channels. We have divided up the BD
> and some of the shielding around the BD into sub regions in order to use
> the results for thermal analysis.
>
> Here is the description of the strange behaviour (as best as I can
> describe it). The beam spot area (BS) where the beam hits is at an
> angle of 3.06 deg. wrt the horizontal plane. The BS is 74 cm long, 4 mm
> high, and 4 cm wide. I have the BS divided up into 16 equal regions:
> BS1-BS16 (see attachment please).
>
> When I look at the Beam Particle distribution (usrbin), I see the beam
> go through all of these regions as expected but when I look at deposited
> energy in BS4, BS8, BS12, and BS16 (stacked up vertically), I see zero
> deposited energy. When I look at beam particle and photon fluences in
> these regions, I see distributions that make sense but nothing in BS4,
> BS8, BS12, and BS16. How could this be???
>
> Another related oddity is that I see similar behaviour in the lead
> shielding that lines up with these regions - longitudinally: PbSh1_6,
> Pb_Sh1_14, PbSh1_22 (see attachment please). The only common thing
> between these lead regions and the beam spot regions where I see no
> deposited energy or beam particle/photons is that they share the same
> two planes as the boundaries in x (longitudinally). I have not done
> anything special with these regions - physics-wise, thresholds, etc. I
> see both neutron and photon fluences (using usrbin) in these lead
> regions and the adjacent regions show deposited energies but not
> these... This does not make any sense.
>
> EMF-cut is set to 100 keV for e+, e- and 10 keV for photons.
>
>
> I would like to know whether this is a bug in FLUKA or some silly
> mistake from my part (which I can't seem to find).
>
> Thanks and best wishes,
> Mina
Received on Fri Aug 23 2013 - 15:49:30 CEST