Detector, Ultraviolet, Channeltron

One of a set of specialized ultraviolet detectors in the collection. These channeltron tubes are typical of those used in the Orbiting Solar Observatories (OSO) project in the early space program. These tubes were used to convert and amplify ultraviolet radiation into electrical signals that could then be telemetered back to earth for further study. The design of these Bendix tubes is based on a similar principle to the photomultiplier tubes used to convert visible light into electric signals. This example is equipped with an attached preamplifier circuit. It was transferred to NASM in 1988 by NASA (GSFC). It is now stored at the Garber Facility.

This channeltron consists of a hollow curved tube of semiconductive glass sealed at both ends. When a photon strikes the inner surface of the evacuated tube it causes additional electrons to be released from the surface. The electric potential that is set up between the ends of the tube by an applied voltage accelerates those electrons towards the other end of the tube. These release additional electrons each time they strike the walls. The resulting cascade of charges has the net effect of greatly amplifying the signal from the initial ultraviolet photon. The total signal is collected by the anode at the end of the tube for further processing. The channeltron is curved to prevent backscatter of charge from ions that may result from ionization of residual gas molecules in the evacuated tube.