[gate-users] Vacuum is not empty

[Sebastien JAN]

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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