GB314096A - Improvements in and relating to light-sensitive discharge apparatus - Google Patents

Abstract

314,096. British Thomson-Houston Co., Ltd., (Assignees of Koller, L. R.). June 22, 1928, [Convention date]. Vacuum tubes.-A discharge device has a cathode 2 emitting electrons at a dull-red temperature, an anode 3, and a control electrode 5 consisting of a monatomic film of light-sensitive material, for example an alkali metal, such as caesium or rubidium deposited in the form of a band on an elongated glass or quartz envelope between the cathode and the anode. The electrode 5 may be formed by depositing a film of silver chemically or electrically, and heating a mixture of caesium dichromate and silicon in a capsule 6, caesium being deposited on the film of silver and excess of caesium being removed by evacuation. The electrode 5 should be arranged as far as possible from the cathode. The cathode consists of a nickel or platinum filament coated with alkaline earth material such as oxide for example by applying a paste of barium hydroxide, nitrate or resinate and heating to 800‹C. Several such layers or alternate layers of barium and strontium oxide may be superposed. The outside of the envelope may be painted black, and light may be admitted through a slot or circular opening in the electrode 5. The device may be used for controlling a relay through a thermionic valve. Specification 303,476 is referred to.