  The light yield of a water-based Cherenkov detector can be significantly
improved by adding a wavelength shifter. Wavelength shifter (WLS) molecules
absorb ultraviolet photons and re-emit them at longer wavelengths where typical
photomultiplier tubes are more sensitive. In this study, several wavelength
shifter compounds are tested for possible deployment in the Sudbury Neutrino
Observatory (SNO). Test results on optical properties and chemical
compatibility for a few WLS candidates are reported; together with timing and
gain measurements. A Monte Carlo simulation of the SNO detector response is
used to estimate the total light gain with WLS. Finally, a cosmic ray Cherenkov
detector was built to investigate the optical properties of WLS.
