This example presently illustrates the following basic concepts, and in particular (indicated with ***), how to use G4 for optical photon generation and transport. Other extended example of what is possible in Geant4 with optical photons can be found at examples/extended/optical/LXe and wls

main()

Define Random Number generator initial seed

G4OpticalPhysics

The G4OpticalPhysics physics class is used. The messenger is the G4OpticalParametersMessenger class.

Define particles; including - *** G4OpticalPhoton ***
Define processes; including
- *** G4Cerenkov ***
- *** G4Scintillation ***
- *** G4OpAbsorption ***
- *** G4OpRayleigh ***
- *** G4OpBoundaryProcess ***

A messenger command allows to define interactively the verbose level and the maximum number of Cerenkov photons per step (see for instance OpNovice.in)

G4VUserDetectorConstruction

Define material: Air and Water
Define simple G4box geometry
- *** add G4MaterialPropertiesTable to G4Material ***
- *** define G4LogicalSurface(s) ***
- *** define G4OpticalSurface ***
- *** add G4MaterialPropertiesTable to G4OpticalSurface ***

alternatively the Configuration can be read from a gdml file. The provided gdml file NoviceExample.gdml corresponds to the detector defined in OpNoviceDetectorConstruction.

G4VUserPrimaryGeneratorAction

Use G4ParticleGun to shoot a charge particle into a Cerenkov radiator

A messenger command allows to define interactively the polarization of an primary optical photon (see for instance optPhoton.mac)

G4UserRunAction and G4Run

Used to accumulate statistics.

G4UserStackingAction and G4UserEventAction

Show how to count the number of secondary particles in an event

Visualisation

The Visualization Manager is set in the main(). The initialisation of the drawing is done via a set of /vis/ commands in the macro vis.mac. This macro is automatically read from the main in case of interactive running mode.

The detector has a default view which is a longitudinal view of the tank.
The tracks are drawn at the end of event, and erased at the end of run.

How to start

compile and link to generate an executable

This example handles the program arguments in a new way. It can be run with the following optional arguments:
```
   $ OpNovice  [-g gdmlfile] [-m macro ] [-u UIsession] [-t nThreads]
```
The -t option is available only in multi-threading mode and it allows the user to override the Geant4 default number of threads. The number of threads can be also set via G4FORCENUMBEROFTHREADS environment variable which has the top priority.
execute OpNovice in 'batch' mode from macro files
```
   $ OpNovice -m OpNovice.in
```
execute OpNovice in 'batch' mode from macro files using a gdml file to define the geometry $ OpNovice -g NoviceExample.gdml -m OpNovice.in

execute OpNovice in 'interactive mode' with visualization

$ OpNovice
....
Idle> type your commands. For instance:
Idle> /control/execute optPhoton.mac
....
Idle> exit

Macros

The following macros are provided:

optPhoton.mac: Shoot optical photons with energy 3 eV
OpNovice.in: Shoot positrons with energy 500 keV.
gui.mac: Configure the graphical user interface.
vis.mac: Configure visualization.

gdml files

NoviceExample.gdml: example gdml file corresponding to OpNoviceDetectorConstruction