Measurement of photocathode spectral response at cryogenic temperature

Noble-gas liquids, such as xenon and argon, have been recently proposed as light scintillators in some experiments dedicated to neutrino physics and dark matter research. These experiments need the use of photomultiplier tubes directly immersed in the liquid phase and operating at cryogenic temperatures. We carried out an investigation about the spectral response and its variation from room to cryogenic temperature for two different kind of cryogenic photocathodes manufactured by Electron Tubes Ltd. and Hamamatsu Photonics K.K. Measurements were carried out by means of a xenon continuous lamp and a UV-VIS monocromator which allows the analysis from 300 to 700 nm with 5 nm resolution. Cryogenic tests were made at the liquid nitrogen temperature (77 K).