Abstract: Provided is a photomultiplier tube including: a container including a window portion formed of a light-transmitting material, and a tubular portion that is connected to the window portion and defines a vacuum space in combination with the window portion; a photoelectric surface that is formed of a photoelectron-emitting material consisting of sodium, potassium, and antimony, is provided on a first surface of the window portion on a side of the vacuum space, and emits photoelectrons in correspondence with incident light; and an electron multiplier that emits secondary electrons in correspondence with incidence of the photoelectrons emitted from the photoelectric surface, and multiplies the secondary electrons. An aluminum oxide layer is formed between the photoelectric surface and the window portion and on a surface of the tubular portion.

Abstract: The electron tube includes a vacuum container having a light transmitting substrate, a photocathode provided on an inner surface of the light transmitting substrate, an anode provided in the vacuum container, and a prism. The prism includes a bottom surface bonded to an outer surface of the light transmitting substrate, a light incident surface, and a light reflecting surface configured to further reflect light, which is incident to the photocathode through the prism and the light transmitting substrate and reflected at an interface between the photocathode and the vacuum space, so that the light is re-enter the photocathode. The light reflecting surface has an outwardly convex curved surface shape. The light incident surface is located inward of an imaginary spherical surface that is along the light reflecting surface.