Optical photons

You may add the physics of optical photons to any physics list including the command:

/gamos/physics/addPhysics opticalphoton

This will activate the scintillation process for all the particles and the G4OpAbsorption, G4OpRayleigh and G4OpBoundaryProcess processes for optical photons. To avoid blowing up the memory by the thousands of optical photons that may be created at one step, by default the secondary optical photons are tracked at the moment they are created; this means that the primary particle is stopped and later it is restarted. You may deactivate this option with the parameter

/gamos/setParam GmPhysicsOpticalPhoton:TrackSecondariesFirst 0

The yield factor, i..e the number of optical photons created per MeV, is set by default to 1, you may change it with the parameter

/gamos/setParam GmPhysicsOpticalPhoton:YieldFactor FACTOR

To define the optical properties of the medium, you must create a G4MaterialPropertiesTable which is linked to the G4Material in question (without it no optical photon will be created). All the properties can be managed in the geometry text file, using tags similar to those of the geometry text file utility. For details on the meaning of these paramters please refer to the Geant4 documentation. We describe here these tags with the parameters that should accompany them.

To define a new G4MaterialPropertiesTable you have to use the tag:

:MATE_PROPERTIES_TABLE

Then you can add different properties to the table. There are two kinds of properties: those that are defined by a single number (called constant properties in Geant4 notation) and those that are defined by a list of numbers, one associated to an energy.

To define a constant property the following tag must be used:

:MATEPT_ADD_CONST_PROPERTY

To define non constant properties, you have to define first the list of energies that you will use to assign the different properties to the table:

:MATEPT_ADD_ENERGIES

Then to define a property:

:MATEPT_ADD_PROPERTY

The material properties table can be attached to a material with the tag (use it several times to attach it to several materials:

:MATEPT_ATTACH_TO_MATERIAL

You can create an optical surface with the tag:

:OPTICAL SURFACE

Optionally the polish value and the sigma alpha value can be set by adding two exta arguments:

The material properties table can be attached to a optical surface with the tag (use it several times to attach it to several optical surfaces:

:MATEPT_ATTACH_TO_OPTICAL SURFACE

You can create a logical border surface with the tag:

:LOGICAL_BORDER SURFACE

You can create a logical skin surface with the tag:

:LOGICAL_SKIN SURFACE

Using optical photons as primary generator

If you are using optical photons as primary generator particles, you may set the polarization using the parameter (see chapter on Generator):

/gamos/setParam SOURCE_NAME:Polarization POLARIZ_X POLARIZ_Y POLARIZ_Z