GB1263766A - Improvements in or relating to electron discharge tubes - Google Patents

Abstract

1,263,766. Magnetrons; cooling cathodes. ENGLISH ELECTRIC VALVE CO. Ltd. 6 July, 1970 [16 Sept., 1969], No. 45692/69 Heading H1D. The cathode 1 of a crossed-field microwave tube-as shown, a magnetronis in good heatexchanging relation with, and is supported by, a closed hollow container 2 which contains a quantity of a material 10 having a boiling point approximately equal to the desired cathode operating temperature, and which acts as a boiler and condenser for the material when the tube is operating, whereby, due to the cooling of the cathode and the stabilization of the cathode temperature, the power dissipation of the tube is increased. The material 10 may be sodium, potassium, caesium, rubidium, lithium, or an alloy thereof. In the arrangement shown, the container includes a chimney 8 having apertures 9, the portion of the container above the apertures acting as the condenser; the inner wall of the container is grooved as at 2A, or is provided with wire mesh, to assist splashing movement of the boiling liquid and prevent the retention of vapour layers or bubbles; and the container is cooled by radiation to the polepiece 13 which is itself cooled by a circulating coolant in pipe 17. In modified arrangements, the top sealing plate 5 of the container is of conical form and is cooled by the circulation of air or water (Figs. 2 and 3, not shown); the chimney 8 is dispensed with, and the container is in the form of a simple cylinder having a tubular wick of asbestos, ceramic, or stainless steel wires, extending between its two ends to return liquid condensed at one end of the container to the other end by capillary action, whereby the discharge tube may be used in any position (Fig. 4, not shown); and heating resistors mounted either axially within an annular boiler condenser container (21, Fig. 5, not shown), or mounted outside the container (22, Fig. 6, not shown) are provided in the case of tubes which will not start from cold. In arrangements in which forced cooling of the condenser is employed, or if the material 10 is solid at room temperature, the forced cooling must be switched off prior to switching off the discharge tube, or an auxiliary heater must be provided for use during the switching off period, to prevent the material freezing and remaining in the condenser.