[Gate-users] No annihilations in the phantom but just in the source

[Uwe Pietrzyk]

Hi,

this is just basic physics! Take a chance and find out, what happens,
when you take "Vacuum" or "Air" or Water as material in the phantom. In Plexiglas,
the positron easily finds an electron and both annihilate and this is the
good reason, why Sodium sources (Na-22) are usually encapsulated
in Plexiglas to yield a real point source. In your case, starting from the source,
the positron cannot go far enough to experience scatter in the phantom, but
undergoes annihilation with an electron right away.

Hope this helps.

Kind regards,

U. Pietrzyk

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On 30.06.2010, at 10:59, Dimitri DWORAK wrote:


Hi

I have simulated a spherical source  of F18 with a radius of 0.5mm in a Phantom of Plexiglas but when i plot all
positions of annihilation between positrons and electrons giving by the Singles file i see that all annihilations are
in the source (graph is attach to the mail ) they are no scattering of positrons in the phantom.

I have check my physic list and the Multiplescattering  option for e+ and e- is in it.

Could you help me please?

DWORAK Dimitri


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