[Gate-users] variance reduction techniques: small field simulations

[G Tom]

HI all,

I am trying to improve my simulations with  variance reduction techniques.

The simulation uses particles from a phase space source just above the
jaws. However, because of the size of the jaws (5cmx5cm opening) and SRS
cone (10mm) , only a small fraction of particles make it through the jaws
to the tungsten SRS cone aperture below. Very few photons actually reach
the dose measurement box below.

What are some ideas to improve the statistics in the dose measurement
volume ? One way is to choose particles that have a higher probability  of
reaching that cone opening. How is that implemented in Gate ? Are there
other VRTs in GATE that will help here?

Below is my setup with the jaws and cone. I show a few photons (green)
stopped by the upper  jaws before making it to the SRS cone (blue/Grey)
below.

Thanks a lot



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