[Gate-users] Re : unwanted scatter events in primary spectrum
Samuel BURG
samuel_burg at yahoo.fr
Tue Aug 31 10:08:44 CEST 2010
Hi Simon,
Hi all,
| Also, did you use the /gate/.../gps/.../monoenergy command ???
I have the same issue using those both version of script (home made script or
the benchmark) :
a)
/gate/source/addSource Source
/gate/source/Source/gps/particle gamma
/gate/source/Source/setActivity 1000000. Bq
/gate/source/Source/gps/energy 140.51 keV
/gate/source/Source/setForcedHalfLife 21636 s
/gate/source/Source/gps/type Point
/gate/source/Source/gps/centre 0. 0. 10. cm
/gate/source/Source/gps/angtype iso
/gate/source/Source/gps/mintheta 0. deg
/gate/source/Source/gps/maxtheta 180. deg
/gate/source/Source/gps/minphi 0. deg
/gate/source/Source/gps/maxphi 360. deg
/gate/source/Source/gps/centre 0. 0. 10. cm
b)
/gate/source/addSource Source
/gate/source/Source/gps/particle gamma
/gate/source/Source/setActivity 1000000. Bq
/gate/source/Source/gps/energytype Mono
/gate/source/Source/gps/monoenergy 140.51 keV
/gate/source/Source/setForcedHalfLife 21636 s
/gate/source/Source/gps/type Point
/gate/source/Source/gps/centre 0. 0. 10. cm
/gate/source/Source/gps/angtype iso
/gate/source/Source/gps/mintheta 0. deg
/gate/source/Source/gps/maxtheta 180. deg
/gate/source/Source/gps/minphi 0. deg
/gate/source/Source/gps/maxphi 360. deg
/gate/source/Source/gps/centre 0. 0. 10. cm
Nota : the Gate user guide is not very explicit about this point : what append
if we do not set
/gate/source/Source/gps/energytype something
and we directly use
/gate/source/Source/gps/energy 140.51 keV
both version are used in the user guide, and no comment is done about the 2
versions.
On Tue, Aug 31, 2010 at 3:16 AM, Simon Stute <gate.stute at gmail.com> wrote:
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 ??
>:-)
>
>With such a configuration the % of "wrong event" is much smaller. Seems to be an
>interesting result.
>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.
>
>I have set a huge cristal (2m*2m*2m) and put a Point source in the center of it,
>then there is no more unwanted event.
So It seems that there is something with the scattering process in the cristal,
some events/particles seems to escapes after scattering when the crystal has
normal size and the source is "outside" the crystal.
We have narrow the problem but it doesn't explain why those events/particles are
not registered as scattering events in the crystal ??
>And did your Tc99m emit only 140,5 keV gamma rays ??
>
>I only set the source to emit 140.5 KeV, yes ;-))
>At least, use the G4tracking verbosity, set a pause after each singles detection
>with an abnormal energy, and track the particles by your eyes :-)
>
>Well not for today this option.
Hum, and in fact I have never use that, can some one send me a sample and
explain how to use this debug mode ?
>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 --
>>-----------------------------------------------------------
>>
>>
>>
>>
>>_______________________________________________
>>Gate-users mailing list
>>Gate-users at lists.opengatecollaboration.org
>>http://lists.opengatecollaboration.org/mailman/listinfo/gate-users
>>
>
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