A new surface parameterization for modeling thin layers of reflector material in the DETECT2000 optical modeling program

A new surface parameterization has been implemented in DETECT2000 that allows for the efficient representation of a thin film of reflector material with non-negligible transmission. Material is usually modeled in DETECT by specifying the optical attenuation and scatter lengths. For a material such as Teflon, commonly used as a reflector material for nuclear medicine scintillators, the scatter length can be very short. Modeling the propagation of photons in a material with a very short scattering length can be computationally intensive as there can be many scatter interactions before the photon either exits the material or is absorbed. In a detector design that makes generous use of Teflon, most of the computations can be spent simply transporting photons in the Teflon. To address this issue, a parameterized surface has been implemented which is specified not by the bulk optical scatter and attenuation lengths, but rather by a reflection and transmission coefficient. This allows computationally efficient modeling of thin film reflectors where surface properties and transmission are relevant.