The use of the continuous resistive channeltron ® electron multiplier in optical detectors

A new optical-detector has been developed which employs a Channeltron multiplier as the electron-multiplying element. The Channeltron multiplier, which is now extensively usod in space-applications to detect charged particles and low-energy radiation in open-window detectors, has been coupled in a vacuum tube with a photocathode responsive to visible and near-ultraviolet radiation. The result is a small, high-gain, low-noise, highly sensitive, extended-red-responsive S-20 photomultiplier tube. The overall length of the tube is about 2 inches, and its diameter is about 1 inch. Only four electrical connections are required. The photocathode, which is processed externally with respect to the tube-envelope, is masked-off so that only a circular area 1 mm in diameter is used. Freedom from excessive alkali vapors, the small photocathode-area, and the inherently-quiet Channeltron electron-multiplier enable the tube to operate at room-temperature with dark-counts on the order of 10 counts/secord or fewer. Magnetic fields and electrostatic fields have little effect on tube-performance. Gains in excess of 10⁷are readily obtainable.