Enhanced quantum efficiency bialkali photo multiplier tubes

Currently, the classical PMTs with semitransparent bialkali photo cathode show peak quantum efficiency (QE) of ∼25–27%. Although the above-mentioned peak QE was achieved already ∼40 years ago, nevertheless one cannot report any significant increase since then. A couple of years ago we started a development program with the main PMT manufacturers Photonis, Electron Tubes and Hamamatsu, aiming to boost-up the peak QE of the (1–2)″ size bialkali PMTs. Today we want to report that our efforts were successful: all of the three above-mentioned companies succeeded to boost the peak QE of bialkali PMTs to the level of 30–35%. In this report, we want to show the QE measurements of different tubes and discuss the future prospects. For example, it shall be possible to use the diffuse-scattering matt lacquer coating technique in order to enhance further the QE. In our previous experience application of that coating provided ∼15% increase in QE for 1–1.5″ hemispherical tubes.