A method to enhance the sensitivity of photomultipliers for Air Cherenkov Telescopes by applying a lacquer that scatters light

The sensitivity of photomultipliers (PMT) can be substantially increased by applying a light scattering lacquer doped with a Wavelength Shifter. Applying this method to the Electron Tubes 9116/17A PMT resulted in a good sensitivity in the short wave UV range as well as a 15–20% increase in quantum efficiency above 350 nm. Details of the procedure and a simple model for the explanation of the enhancement are presented.