Optimal light collection from diffuse sources: application to optical fibre-coupled luminescence dosimetry

A model is developed to evaluate the light collection of a diffuse light source located at the tip of an optical fibre. The model is confirmed experimentally and used to evaluate and compare the light collection efficiency of different fibre-coupled luminescence dosimeter probe designs. The model includes contributions from both meridional and skew rays, and considers the light collection from an optically attenuating scintillator. Hence the model enables the optimisation of different, but useful and new probe materials such as BeO ceramic. Four different dosimeter architectures are considered, including previously investigated probe designs; the butt-coupled and reflective wall, along with two novel designs. The novel designs utilise a combination of the scintillating material and transparent media to increase the light collection. Simulations indicate that the novel probes are more efficient in light collection for applications in which it is necessary to minimise the volume of the scintillating material.