Development of a photomultiplier tube with high quantum efficiency

We propose a new method to significantly increase the quantum efficiency of a photomultiplier tube by employing a multi-photocathode and a mirror to produce photoelectrons by reusing photons transmitted by a single photocathode. In order to estimate the expected performance of the new photomultiplier, we studied the spectral responses of the reflectance, transmittance, and quantum efficiency of a K2CsSb photocathode as a function of the wavelength of incident light. A large enhancement of the quantum efficiency is expected in the regions between λ=280 and 650 nm.