Optical properties of UV transmitting acrylics for use in a heavy water Cerenkov detector

The absorption, refraction, and scattering properties of several UV transmitting acrylics have been investigated over the wavelength range 300-700 nm using a combination of near-normal incidence regular transmittance and reflectance and diffuse-only reflectance measurements, followed by a Fresnel and a Kubelka-Munk analysis. The samples were evaluated in the as-cast and thermoformed forms, and both before and after an accelerated aging procedure. The results show significant differences in the optical behavior of the various acrylics in the UV region and stress the importance of carefully characterizing acrylic from different sources for each intended use. In our case, acrylic is the proposed material for a heavy water containment vessel for the detection of solar neutrinos. The significance of our findings to the overall performance of this Cerenkov detector, known as the Sudbury neutrino observatory detector, is discussed.