A light sensitive tube that can detect very low light levels by amplifying the signals applied to it PMTs, are almost always used with drum scanners
A vacuum encapsulated photocathode from which electrons are ejected by the photoelectric effect followed by multiple cathodes from which many additional electrons are emitted in a cascade When finally collected, the original single electron may have generated a pulse of over one million electrons
A light sensing device use in drum scanners that's capable of measure extremely low levels of light