GB790416A - Improvements in or relating to electron discharge devices incorporating electron multipliers - Google Patents

Abstract

790,416. Electron multipliers: cathode-ray tubes. ELECTRIC & MUSICAL INDUSTRIES, Ltd. May 26,1954 [June 5, 1953], No. 15508/53. Class 39(1). An electron discharge device has a photocathode 3 for generating an electron image, electron multiplying means 4 for intensifying the electron image, and a target 8 wherein the multiplying means 4 comprises a plurality of secondary emitting electrodes 5<SP>1</SP>-5<SP>12</SP> each comprising a large number (at least a thousand) of secondary emitting elements in a two-dimensional array and formed as side surfaces of passages through the respective electrode, and the electrodes being disposed so closely adjacent one another with the entrance aperture to each passage in each electrode except the first so aligned with a corresponding individual exit aperture of a passage in the previous electrode that when the device is connected in circuit electrons representing different image points pass directly from one electrode to the next in virtually single streams confined by the passages, thereby reducing mixing of the electrons corresponding to different image points. The target 8 can be a fluorescent screen or a charge storage electrode. A transparent conductive layer 9 can form a backing to the target 8. An accelerating coating electrode 6 and a focusing electro-magnet 7 are provided for producing a linear magnification of five, ten or more of the electron image projected on to the target 8. Each secondary electrode 5<SP>1</SP>-5<SP>12</SP> comprises an array of parallel slats 11 each inclined, e.g., at 45 degrees to the path of the electrons and a further array of parallel slats 14 perpendicular to the first slats forming passages oblique to the electron paths. The slats 11 and 14 produce focusing fields which steer the secondary electrons representing different image points directly from one electrode 5<SP>1</SP>-5<SP>12</SP> to another. The effective area of the photo-cathode may be 2" square and of each electrode 5<SP>1</SP>-5<SP>12</SP>, 10" square. The aperture of each passage formed by the slats 11 and 14 may be 0À1" x 0À1" and there may be 10<SP>2</SP> slats 11 and 10<SP>2</SP> slats 14 giving 10<SP>4</SP> passages. A fine pitch low-shadow ratio mesh 12 extends in front of each electrode 5<SP>1</SP>-5<SP>12</SP> to prevent suppression of secondary, electrons liberated from the respective electrode by penetration of the relatively negative electrical field from the previous electrode. Each mesh 12 is carried on horizontal extensions 13 projecting forwardly from the inclined slats 11. The device can be used for X-ray image intensification, for direct visual observation, in photography, as an ultra-violet light microscope by making the end wall 2 of quartz, or as a television pick-up tube when the target 8 is a charge storage electrode which can be scanned with a beam of electrons preferably of low velocity. The device can also be used in colour television to give successive pictures in red, blue and green which are directed by shutters sequentially into three pick-up tubes from which picture signals are derived by conventional scanning.