High Reflectance Coatings

To help maximize the photon statistical accuracy and uniformity of pulse height measurements from a Cerenkov detector, coatings of high reflectance were made and procured. A number of various combinations of pigments and binders were tried. Reflectances of these and various ready-made coatings were measured as a function of wavelength. From these measurements, an effective absorptance was calculated assuming an S-ll response and Cerenkov spectrum for each coating. Comparison led to the conclusion that Alucer MC alpha alumina from France is the best of the pigments tried. This pigment ground with Sylvania PS7, a potassium silicate, produced coatings with absorptances between .03 and . 04, nearly as low as that of freshly smoked magnesium oxide and several times lower tharn those of special high reflectance commercial coatings.