Perhaps the simplest fully-featured G4 application.
Based on one-file simulation by Jason Detwiler.
Installation: Compile geant4 with GDML support (and optionally HDF5 support), then do:
source (g4install_path)/share/(g4version)/geant4make/geant4make.sh
(or source (g4install_path)/share/(g4version)/geant4make/geant4make.csh)
make
Physics List: uses Geant4's named physics lists, set them using macro commands (see example run.mac)
Generator: uses Geant4's GPS. Set it up using macro commands (see example run.mac).
Geometry: uses GDML (see example run.mac). Can use materials from Geant4's NIST Material Database (note: the GDML parser will complain that the materials have not been defined, but Geant4 will still run without error). Also supports Geant4's text file geometry scheme.
Output: uses Geant4's analysis manager (root, hdf5, xml, csv), with several configurable options for output format, sensitive volumes (including regex-based pattern matching / replacement), etc. (see example run.mac). Records event/track/step numbers, PIDs (see also the python package particle), positions, energies, etc.
Other macro commands: see the example run.mac, or run g4simple and type "help" and choose the g4simple option. Note: more commands become available after setting a physics list.
Visualization: uses available options in your G4 build (see example vis.mac).
Postprocessing: you will want to postprocess the output to apply e.g. detector response. See example code that runs on the output of run.mac.
Ouput parameters:
- int nEvents: number of events run in the simulation
- int event: event number of the recorded step
- int pid: particle ID of the particle making the step
- int trackID: track ID for the recorded step
- int parentID: parent track ID of the track being recorded
- int step: current step number
- double KE: kinetic energy at the start (step=0) or end (step>0) of the step
- double Edep: energy deposited along the step
- double x: global x coordinate of the pre- (step=0) or post- (step>0) step position
- double y: global y coordinate of the pre- (step=0) or post- (step>0) step position
- double z: global z coordinate of the pre- (step=0) or post- (step>0) step position
- double lx: local x coordinate of the pre- (step=0) or post- (step>0) step position
- double ly: local y coordinate of the pre- (step=0) or post- (step>0) step position
- double lz: local z coordinate of the pre- (step=0) or post- (step>0) step position
- double pdx: global x component of the pre- (step=0) or post- (step>0) step momentum
- double pdy: global x component of the pre- (step=0) or post- (step>0) step momentum
- double pdz: global x component of the pre- (step=0) or post- (step>0) step momentum
- double t: global time of the pre- (step=0) or post- (step>0) step point
- int volID: the ID of the volume being traversed (user-defined) (see example run.mac)
- int iRep: the replica number of the volume being traversed
You can turn on and off different output fields using the macro silenceOutput/addOutput macro commands (see examples in run.mac).
Note: Each pair of rows in the output corresponds to the pre- and post-step point of the corresponding step, with the step number, Edep, and volume traversed for the step recorded along with the post-step. Note that this means that volume ID changes occur at the first step point inside a volume, not at the point recorded on the boundary. This may be counter-intuitive for those familiar with G4, where the step point on the boundary is marked as being "in" the volume being entered.
For every energy-depositing particle traversing a sensitive volume, the g4simple output will include the step info for the first step point in the volume. If the previous volume was not a sensitive volume, that step will have Edep = 0.
See similar project by Jing Liu at https://github.com/jintonic/gears