Radiation Effects on Multiplier Phototubes

A multiplier phototube is an extremely sensitive device used to measure ultraviolet, visible and near infrared radiant energy. Physically, multiplier phototubes are high vacuum tubes which are comprised of a photo-cathode; an electron lens, which directs the photo-electrons onto the first dynode; a series of dynodes or amplifying stages; and an anode or collector. The use of multiplier phototubes in photometric and nuclear detectors for satellite systems has increased dramatically within the last few years. Because many of these systems are subjected to either natural or artificially created radiation, such as encountered in the Van Allen belts, or the South Atlantic anomaly, or galactic or solar cosmic radiation, a study of the behavior of these tubes under such conditions has become necessary. This paper summarizes the work of EMR and that of many other investigators, and discusses degradation of optical windows used; effects on photocathodes and dynodes; effects on noise, dark current and resolution. A list of conclusions is given.