A method to enhance the sensitivity of photomultipliers for air Cherenkov telescopes

摘要

A simple method to enhance the sensitivity of photomultipliers (PMTs) will be described. The method is based on applying onto the cathode window a specially prepared lacquer containing a wavelength shifter (WLS). A rapidly evaporating lacquer solvent results in a milky surface that acts as a photon scatterer. Applying the method to the ET 9116A PMT (hemispherical borosilicate window and rubidium-bialkali photocathode) resulted in a good sensitivity in the short-wave UV range as well as a approx>20% increase above 330 nm. Details of the study, the procedure and a simple model for the explanation of the enhancement are presented.