GB1353547A - Electron tube - Google Patents

Abstract

1353547 Velocity-modulated tubes VARIAN ASSOCIATES 16 June 1971 [29 June 1970 16 Nov 1970] 28150/71 Heading H1D A discharge tube includes an electron gun in which the cathode is insulated from the anode by a hollow flared insulator having an encircling external projection which is joined to a portion of the tube envelope which is insulated from the cathode. As shown, the frusto-conical insulator 22, of alumina or beryllia ceramic, is sealed, by welding, at its shoulder 23 to the soft iron anode 16 having a copper insert 17 and, at its inner end, by a flanged member 34 to the beam control electrode 33, which is itself sealed to but insulated from a focus electrode 38 which supports a focus grid electrode 46 operated at cathode potential and having its apertures aligned with those of a control grid 11. Electrodes 33 and 38 both have soft iron jackets 35 and 45, respectively, around their aperture ends, to assist in beam shaping. Downward radiation from the cathode heater 15 is prevented by a plurality of molybdenum or nickel heat shield discs 49 electrode 33 is provided with a rearwardly projecting cooling fin 36, which also acts as part of the lead 37 for the electrode; an alumina coolant enclosure 61, having inlet and outlet ports 65 and 66, respectively, is secured by screws 64 to the rear face of the anode; and the ceramic back-up ring 28 and positioning ring 29 reduce thermal stress on the sealing flanges 24, 26. In a modified embodiment (Fig. 3, not shown), the coolant enclosure 61 is completely sealed, contains a perfluorinated liquid coolant, has an end wall of rubber to permit expansion, and supports cooling fins on its outer surface. In a further embodiment (Fig. 4, not shown), the gun is housed at the upper end of the discharge tube, and is provided with boiler and condenser enclosures thereabove, the condenser being finned and having an expansion chamber terminated by a metal bellows. As described, the gun is incorporated in a magnetically-focused klystron (Fig. 1, not shown), but reference is made to its use in a travelling wave tube and magnetron.