Generation of Scintillation light

The generation of scintillation light is handled by EGS4_AUSGAB1. This routine makes a call to SCINTILLATE which will return the number of generated photons per MeV for the required medium (zero if no scintillation) and also Birks' constant. The required number of scintillation photons are packed into a Cerenkov bundle vertex. When VXCERN adds tracks to the photon creation vertex, it makes a call to SCINT_WL which randomly selects the wavelength for each photon from the specified primary emission spectrum, or returns zero if there is no scintillation. If scintillation is present, the photon directions are chosen randomly since scintillation light is isotropic, rather than the usual Cerenkov distribution.
When the cerenkov vertex is unpacked by UNPCER, a call is made to SCINT_TIME which randomly selects the emission time of each photon from the primary scintillation timing distribution. If scintillator is not present, SCINT_TIME returns zero and the normal Cerenkov timing distribution is used.