I am working on a specific simulation that is modified from the Magnetic Monopole code in Geant4 (/extended/exoticphysics/monopole). This simulation contains the geometry of a long (2-3m), thin (~1mm) cylindrical pipe made from Beryllium. I am propagating monopoles, initially from vacuum, towards the pipe. The simulation has a strong magnetic field of a few teslas along the z direction. The trajectories are curved due to the magnetic field. I understand that in vacuum, the monopole is expected to take a very long steps, if any. However, when it enters the beryllium volume (1mm thickness), I should be able to control the step length and the number of steps it takes in the volume, before the particle exits. However, no amount of stepping parameters that I change has any effect on the step-size.
I have attached
the stepping verbose of two monopoles, which take 3-4 steps in the pipe volume before they exit. I would like to decrease the step size and have the particles take a larger number of steps in the simulation (sure, it will increase the simulation time, but also the accuracy of results).
For decreasing the step-size, thus far, I’ve tried the following (but the modification does not affect the simulation).
- In the FieldSetup source file (attached), I have changed the fMinStep value of 1mm (default) to a much lower value.
- I included other parameters (from the application developers guide) such as deltaChord, deltaOneStep, deltaIntersection, epsMin, epsMax.
- I have also written a DetectorMessenger with a function SetMaxStepSize (defined in DetectorConstruction) and set it to 0.0001mm using a macro file.
- In the G4mplIonisationWithDeltaModel source code (for monopole ionization), I have changed the emin (LowEnergyLimit) to a very low value ~eV to lower the thresholds in the simulation.
- Similarly, in G4MonopoleTransportation, I had lower the value of fThreshold_Warning_Energy to a few eVs to lower thresholds.
G4MonopoleFieldSetup.cc (4.6 KB)
If anyone could guide me further regarding the changes I could make in the simulation to control (lower) the step-size, I would be very thankful. Let me know if you have any questions.