GB1189353A - Improvements relating to Crossfield Discharge Tube Devices - Google Patents

Abstract

1,189,353. Transit-time tubes. ENGLISH ELECTRIC VALVE CO. Ltd. 29 March, 1968 [4 April, 1967], No. 15264/67. Heading H1D. A crossed-field discharge device includes an annular cathode spaced from an annular anode to form an interaction space which is symmetrical about an axis, the electric field being inclined to that axis at an angle other than 0 degrees and other than 90 degrees when the device is operating. As shown, a magnetron includes an annular cavity 11 in a magnet 10, having a cathode 7 the emissive surface 8 of which is disposed opposite and parallel to the ends of the #/4 long fingers 2 of a slow wave structure supported from an annular waveguide cavity 5. The interaction space is symmetrical about the axis 3, and the walls of the magnet cavity, and the emissive surface of the cathode and the ends of the fingers 2 are shaped, as shown, to ensure that the electric and magnetic fields are mutually perpendicular, with the electric field directed at an angle α to the axis 3. Operation in the # mode is ensured by the provision of slots 6 between every other cavity of the slow wave structure and the fast wave waveguide cavity 5, asymmetry in the size, shape, position or orientation of the slots permitting excitation of only a forward or only a backward wave in the cavity 5, which is coupled to the waveguide 12 by a directional coupler 13. With tight coupling between the slow wave structure and the cavity 5, the device may be tuned either by the introduction into the cavity of a dielectric cylinder, or by forming cavity 5 from ridged waveguide and deforming the wall to which the ridge is attached.