GB628071A - Improvements in and relating to photo-sensitive discharge devices - Google Patents

Abstract

628,071. Photo-electric cells; thermionic valves. BRITISH THOMSON-HOUSTON CO., Ltd. July 25, 1947, No. 20113. Convention date, July 27, 1946. [Glass 39 (i)] A photo-cell and a thermionic gas-filled triode acting as amplifier are contained in separate compartments of the same envelope which is divided by a transverse metallic wall 4. This wall has a central aperture 5, and may be integral with the lower section 8 or with the upper section 11 of the envelope ; in the latter case a window 9 is provided. The upper compartment contains a frusto-conical photo-cathode 13, attached to wall 4 round the periphery of the aperture 5, and a central photo-anode 12 which is supported directly by the cathode 14 in the lower compartment. Concentric with the cathode are an anode 16 and a grid 15, the latter being attached to the wall 4 and thus to photocathode 13. The triode electrodes are supported from an insulating disc 17 through which also pass the various leads. This construction affords improved protection for the photocathode against heat from the triode section, and the protection may be further increased by an asbestos collar 36 mounted in the aperture 5. In a modification, Fig. 3 (not shown), the grid is as before, but the anode is mounted centrally under photo-anode 12, while the cathode is placed eccentrically, outside the grid. The filling may be mercury vaporized from a drop 35, or argon at 100/150 microns, or neon or xenon; alternatively the device may be completely evacuated. The tube may be used in the circuit of Fig. 5 (not shown) to operate a relay in response to a predetermined energy level from a source such as an incandescent or U-V lamp, X-ray tube, &c.