[Gate-users] Scattering in the back-to-back source of gamma quanta

[Andrej Studen]

Maybe others can correct me if I am wrong - but the source defines just 
the distribution of the primary particles (for the ParticleGun object of 
Geant4), and has no relation whatsoever on the material in the vicinity 
of the source. Once the primary particle is created, transportation 
algorithms propagate its path through the volume, occupied by entities 
defined in geometry part of the simulation setup. Hence - if you world 
volume is made of vacuum, and no other volumes were added, the source is 
in vacuum as well.

If you want your source to be of particular material, you have to crate 
a daughter volume of the world volume (see gate manual for exact syntax) 
of an appropriate size and material. Then tracking will use that 
particular material and do Compton/Rayleigh accordingly.

If you want annulus source, you also have to think about material of the 
prohibited volume. I can't really say it should be a particular type 
since I have no idea what you want to simulate.

Hope this helps

Andrej

On 01/08/16 10:06, Pawe Kowalski wrote:
> Hi,
>
> In my simulations I have volume source of back-to-back gamma quanta.
> I would like to ask if this is possible to have some Compton or 
> Rayleigh scatterings in this source?
> If space around source is a vacuum, then source is also treated as a 
> vacuum? Going forward, if space around source is an air, then source 
> is also treated as an air?
>
> My definition of source:
>
> #=====================================================
> # linear source
> #=====================================================
>
> /gate/source/addSource linear gps
>
> /gate/source/linear/gps/type Volume
> /gate/source/linear/gps/shape Cylinder
> /gate/source/linear/gps/radius 3.2 mm
> /gate/source/linear/gps/halfz 35. cm
> /gate/source/linear/gps/pos/centre 0. -45. 0. mm
>
> /gate/source/linear/setActivity 5000000 Bq
> /gate/source/linear/setType backtoback
> /gate/source/linear/gps/particle gamma
> /gate/source/linear/gps/ene/mono 511. keV
> /gate/source/linear/gps/angtype iso
>
> /gate/source/list
>
> Best regards,
> Paweł Kowalski
>
>
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-- 
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dr. Andrej Studen
Jozef Stefan Institute,
Jamova 39, 1000 Ljubljana, Slovenia
Tel.: +386 1 477 3162
       +386 31 822 779 (mobile)	
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