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Idea Re: Optimisation for nanodosimetry in silicon 

Forum: Physics List
Re: Question Optimisation for nanodosimetry in silicon (Pierre)
Date: 23 Jul, 2016
From: Vladimir Ivanchenko <Vladimir Ivanchenko>

Hello,

Nano-dosimetry is not a standard application area of Geant4 EM physics, because for proper simulation in this conditions a standard condense history approach is not applicable. So, instead of energy loss + fluctuation and multiple scattering one should simulate single ionisations and single elastic scatterings. Your case of low-energy muons makes this even more problematic.

If you are using recent versions of Geant4 10.2p02 or 10.3beta you can apply:

G4EmStandardPhysicsSS - single elastic scattering;
G4EmStandardPhysicsGS, G4EmStandardPhysicsWVI - both multiple scattering models have single scattering regime.

For single ionisation you may try out following option:

/process/em/AddPAIRegion all world

this means that PAI model of ionisation will be applied everywhere for all particles. The model can be applied for very small steps, however, I am not sure in quality of simulation for low-energy muons, this needs confirmation, initially PAI is a relativistic model.

An alternative may be MicroElec model for Silicon, however, normally it is not working for muons, some model improvements and configuration improvements are needed. MicroElec may be activated via:

/process/em/AddMicroElecRegion world

but it will not work for muons out of the box, you will need contact authors to clarify possibilities of model extension.

Finally, an important comment: at low energy one should use only NIST materials if available. For example, it is recommended to use "G4_Si" instead of "Silicon".

TestEm7 may be not the best choice, while TestEm5 and TestEm8 may be useful for your study. Unfortunately, without detailed study of this simulation your results will not be reliable.

VI

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