Set StepFunction parameters

Physics Processes, Models and Cross Sections
1

Dear all,

I have a question about the StepFunction.

I’m simulating the propagation of alpha particles in materials with energy in the order of some MeV (3-10 MeV).
I have tried both the EmStandardPhysics and the EmStandardPhysics_option3 physics lists and I have noticed that the number of steps is 1 in the first case and about 3 in the second case.
This is not sufficient for my application, because I need a more accurate energy deposit as a function of energy.

I think that this behavior is due to the StepFunction limitation and to the different StepFunction parameters in these physics lists, right?

I know that the StepFunciton parameters can be changed via the command /process/eLoss/StepFunction, but this command changes only the StepFunction parameters for electron and positron.

The question:
Is there a way to modify the StepFunciton parameters for alpha particles (and maybe other particles) via C++ code (or UI command) without creating my custom physics list? in other words, how to modify the parameters of the EmStandardPhysics lists?

Thank you for your help

Andrea

2

Hi,

I have found that the “SetStepFunctionMuHad” function, available also via UI command, works on the alpha particles.

On which other particles do this function acts?

Instead, the “SetStepFunction” function acts only on electrons and positrons?

Thanks

3

Hello,

you need to use another command, for example,

/process/eLoss/StepFunctionMuHad 0.1 0.01 mm

Another possibility is to add step limitation - this may require more CPU but you will be sure about number of steps.

VI

4

Another possibility is to add step limitation - this may require more CPU but you will be sure about number of steps.

And how to do that?

5

Hello,

there are 3 ways to limit step:

  1. cut in range
  2. StepFunction, with Geant4 10.7 there is UI:
    /process/eLoss/StepFunctionLightIons 0.05 0.01 mm
  3. use step limiters, see examples
    $G4INSTALL/examples/extended/electromagnetic/TestEm5

VI