[Gate-users] Boundary problems at low energies.

[Ludvig Syrén]

Dear all Gate users.

I have ran a simulation with 2 billions monoenergetic photon beam of E=0.1 keV traversing through a geometry of 3 thin air slabs contained in a box of dense air(air with the same density as water).
The geometry should fulfill Fano´s theorem for a photon beam of E=0.1keV. As an actor i have used the dose actor and for the physics i have used Penelope. The dose of the big air box should get a "smoothly declining" behavior but at the boundaries of respective slab i get a peak and a minimum in dose, see attached figure "doseprofile". Have anyone else had this problem? What can i do to fix it?

I have tried to change the "SetCutInRegion" fort the gammas, electrons and positrons to the lowest possible and it seems that it helps a bit but it does not fix the problem. I have also tried to set the "stepHitType" of the detectors to "random" but the peaks are still there.

I have attached settings used for the geometry, beam, detector, materials and main simulation. I have also attached the resulting dose profile from the big air box "doseprofile".

Any ideas on how i can fix this would really be appreciated.

Thanks for help!

Regards,
Ludvig Syrén

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