[Gate-users] unwanted scatter events in primary spectrum

[Simon Stute]

Hi Samuel,

Did you try a point source forced to emit along a line directly in a huge
unique crystal made of a material with extremely high Z, and everything in
vacuum ?? :-)
Otherwise, if it will not result in a "segmentation violation", try the same
experience but defining the world (or an object of the same size than the
world) made of crystal material and attached as crystalSD, and with the
point source inside in the center.

And did your Tc99m emit only 140,5 keV gamma rays ??

At least, use the G4tracking verbosity, set a pause after each singles
detection with an abnormal energy, and track the particles by your eyes :-)

Good luck !
Simon

On Tue, Aug 31, 2010 at 12:47 AM, Samuel BURG <samuel_burg at yahoo.fr> wrote:

>
>
> Hi Gaters,
>
>
> I have a crazy issue with scattering and primary spectra (SPECT simulation
> with
> Tc99m)
>
> when I create a primary spectrum from root data save from a gate simulation
> there are to many events out of the dedicated energy spike, and it look
> like
> event tagged as primary events are in fact scatter events.
>
> this occurred in numerous different situations/configurations. I haven't
> find
> any configuration who doesn't produce such a problem, even with the SPECT
> benchmark.
>
> here's all what I have tested, nothing solving the issue :
> - 32 / 64 bits arch
> - single CPU / SMP / Cluster
> - GATE version 4.0 / 5.1
> - source shape : point / cylinder
> - collimator : with / without
> - PMT back compartment : single volume / complex multi volumes
> - disabling all  non-crystal volume (setting all material to "Air", or
> removing
> all volumes from simulation)
>
> - different energyCut
> - crystal material : NaI / NaI(Tl)
> - with very basic digitizer (only adder) or very complex digitizer (all
> SPECT
> modules but optic tracking)
> - same issue with the benchmark (root output and ASCII output)
> - same results using different fields of the root file to asses with event
> is
> primary or scatter : RayleighVolName, RayleighPhantom, RayleighCrystal,
> comptVolName, comptonPhantom, comptonCrystal
>
> Software versions :
> OS : GNU Linux, Ubuntu 10.4 LTS, x86_64
> GATE : 4.0 & 5.1
> root : 5.20/00      24 June 2008
> clhep : v2.0.3.2
> geant4 : 4.9.1.p02
> gcc : 4.2.x (replacing system default 4.4.x)
>
> What's crazy is that in the sample file
> gate_v4.0.0/benchmarks/benchmarkSPECT/Results_benchmark.doc the primary
> spectrum
> looks like a primary  spectrum, and when I run the benchmark, the primary
> spectrum has some additional scatter event !
>
> So, there is something I really don't understand here, and it turns me
> crazy !
>
> Attached :-> too big files, not attached, use sendspace links below
> - the outputs of the SPECTbenchmark compressed with 7z, ascii files and
> root
> files.
> - screen capt. of the sprectra I have with my own processing and with the
> root
> processing of the benchmark (root output)
> - results of the processing of ASCII output
>
> someone has an idea before I break down ?
>
> Best regards,
>
> Samuel
>
> Link for files on sendspace (ask me if you have any trouble downloading the
> files):
> http://www.sendspace.com/file/vo7sa0
> http://www.sendspace.com/file/0ofue2
> http://www.sendspace.com/file/nvw4ef
> http://www.sendspace.com/file/w1m0va
> http://www.sendspace.com/file/seshz9
> http://www.sendspace.com/file/xck3rt
>
> -----------------------------------------------------------
> Samuel Burg
>
>
> Mail : <samuel_burg at yahoo.fr>
> -----------------------------------------------------------
> "Aw, come on, who would be so stupid as to insert a cast
> to make an error go away without actually fixing the error?"
> Apparently everyone.
> -- Raymond Chen  --
> -----------------------------------------------------------
>
>
>
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