Photoelectric Electron Tubes

Three electrode tubes containing alkali vapor metals or vapor of alloys of alkali metals possessing low ionizing potentials and the characteristics of a photoelectric cell give remarkable results as detectors both in the plain and the oscillating condition with 10 volts on the plate, these detectors are extremely sensitive, at least three times that of the gas content tube. The photoelectric properties cause the tube to function fairly well with zero plate voltage. It is probable that the source of energy in this case is the luminous and non-luminous radiation from the incandescent filament. These tubes also make sensitive amplifiers.