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Aging tests for dielectric-coated aluminum to be used in the Sudbury Neutrino Observatory McGarry, Louis J.


The Sudbury Neutrino Observatory is a heavy water Cerenkov detector designed to detect solar neutrinos. Its main objective is to confirm or negate the solar neutrino problem. To achieve maximum counting rates and, thus, minimum statistical uncertainties, collection of Cerenkov light must be maximized. Our group at UBC, working with collaborators at Oxford, have designed and tested an optical concentrator that couples with a photomultiplier tube to achieve an effective gain in light collection by nearly a factor of 2. We have designed a procedure for measuring the reflectivity of flat mirror immersed in water within the incident angular range of 15° to 750 to facilitate the reflectivity measurement of dielectric-coated aluminum (DCA) mirror—the reflective component in the the concentrators. DCA is a standard product used in lighting fixtures to enhance the total reflected light. We determined that our application would best be served with a dielectric coating that was 10% thinner than standard. Our DCA was manufactured with the thinner coating. To ensure that the mirror will not significantly deteriorate within the 10 year expected life span of the detector, equipment was designed and constructed that accelerates the aging of the mirror, allowing 10 year-equivalent aging to occur in 70 lab-days. The reflectivity of aged mirror was then measured to verify that no significant loss occured.

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