[gate-users] Vacuum is not empty

[jazmin schwartz]

Dear Seb:

Thanks for your response...I actually had done both of the things you 
suggest...but I still get e+ scattering and annihilation within the area 
that is supposedly under vacuum ..... any ideas ???  I expect that the 
e+ should travel in a straight line path while it is in vacuum !!!

Thanks


Cheers
Jazmin

Sebastien JAN wrote:

> Hi Jazmin,
>
> You can find the definition of Vacuum in the GateMaterials.db :
>
> Vacuum: d=0.000001 mg/cm3 ; n=1
>    +el: name=Hydrogen ; n=1
>
> In this database (GateMaterials.db), you can add all sorts of new 
> materials.
>
> A more classical defition of vacuum with a Geant4 description could be 
> the following :
>
>   //
>  //  vacuum
>  //
>
>  density     = universe_mean_density;    //from PhysicalConstants.h
>  pressure    = 3.e-18*pascal;
>  temperature = 2.73*kelvin;
>  G4Material* Vacuum = new G4Material(name="Vaccum", z=1., 
> a=1.01*g/mole, density,
>                     kStateGas,temperature,pressure);
>
>
> cheers
> seb
>
>> Dear All:
>>
>> I was testing some elements in the cylindricalPET module by sending 
>> monoenergetic positrons towards a crystal.  I made all other 
>> materials in my geometry Vacuum.  However, the positrons annihilate 
>> in the supposed Vacuum or a collision every time ..... Has anyone 
>> come across this before ? Is  there a solution ?
>>
>>
>> Thansk !!!!
>>
>> Cheers
>> Jazmin
>>
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>>
>>
>
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