The effect of temperature on the light yield of polystyrene-based scintillating fibers

We have made semi-quantitative calculations of photon attenuation lengths near peak emission wavelengths in polystyrene-based scintillating fibers, based on a model assuming that photon absorption at these wavelengths is primarily due to secondary dye molecules in a particular vibrational level of the ground π-electron state. Since the population density of such molecules depends on temperature through a Boltzmann factor, so too should the single-wavelength attenuation lengths. To test this, we have performed experiments in which we varied the temperature of scintillating fibers doped with butyl-PBD (primary dye) and dimethyl-POPOP (secondary dye) from −30 °C to +50 °C and measured photon attenuation as a function of temperature and wavelength. Our results indicate that photon transmission improves with decreasing temperature, in basic agreement with the functional dependence of the model.