Abstract: A thermionic cathode (FIG. 1) comprises an emitter (3) comprising a matrix (4) of tungsten impregnated with an alkaline earth activator. The matrix is coated with a coating (5) of about 20-30% osmium fully alloyed with tungsten formed by cosputtering osmium and tungsten onto the matrix. A diffusion barrier (6) of osmium may be interposed between the matrix 4 and coating (5) (FIG. 2) and, optionally, osmium may be diffused into the matrix (4). Alternatively the whole matrix may comprise a mixture of about 20-30% osmium fully alloyed with tungsten (FIG. 3). Alternative to osmium and tungsten may be used, and various modifications may be made, and other methods of making the emitter may be used. In particular the proportion of osmium may be about 40%.

Abstract: A thermionic cathode (FIG. 1) comprises a porous matrix of tungsten (4) impregnated with alkaline earth activator.A coating (5) 1 .mu.m thick is formed on the matrix (4). The coating is of .sigma. phase alloy of molybdenum and osmium.Alternative .sigma. phase alloys are disclosed, and various methods of making cathodes are disclosed.

Abstract: A spin tuned magnetron has a spinner the axially facing end of which lies in an inclined plane and an anode vane ring having an annular flange the end face of which lies in an inclined plane so that the amount of overlap of the flange and spinner varies as the spinner rotates. (In the FIG. 4A the spinner and the ring are shown spaced far apart; in practice they are spaced so that the planes coincide when parallel).

Abstract: A spin tuned magnetron (FIG. 2) includes a spinner 3 which interacts with a magnetron cavity to modulate its frequency of oscillation. The spinner runs in bearings 8, 9 around a shaft 7. The lives of the bearings are a controlling factor in the life of the magnetron.The outer races OR are fixed in position relative to each other and to the spinner by spacers, 13, 14 and a spring 15 arranged between an abutment 11 and a circlip 12 on the spinner. The inner races are arranged to be moveable relative to each other and to the shaft by virtue of spacers 10 and 17, a spring 16 between the inner races, and a further spring 18. A pole-piece nose 4 is arranged to be screwed down on the shaft to compress the springs 16 and 18 to provide a desired amount of axial float on the spinner. By setting the axial float the bearing load can be shared as desired and thus increase the lives of the bearings.

Abstract: A thermionic electron emitter comprises a tube of wall thickness less than 0.1 mm, a body of thermionic electron emissive material compressed and sintered in the tube, and a ring, coaxial with the tube, within the body to provide constraint against cracking of the body.

Abstract: An electron emitter comprises field emitter zones formed by projections of field emissive material separated by regions which are not field emissive. An extractor electrode for applying an electric field to the projections and a focus electrode have openings aligned with the emitter zones and material particles aligned with the non-emissive regions. The electrodes form, when suitably energised electron focussing fields to focus electrons emitted from the zones.

Abstract: In a spin-tuned magnetron a plurality of anode vanes disposed in an annulus form resonant cavities and a spinner, carrying a plurality of apertures rotates coaxially with the annulus to pass through the cavities and vary the resonant frequencies. This expedient gives a frequency variation which is predictable. This invention provides a less predictable frequency variation by modifying the shape of at least one of the vanes and at least one of the apertures. The aperture is in one example modified by cutting a slot between one aperture and the edge of the spinner.

Abstract: This relates to coaxial magnetrons and to a tuning arrangement for the stabilizing cavity including a fixed tuning element and a movable tuning element which is continuously and unidirectionally displaceable for repetitive cooperation with the fixed element. The arrangement is particularly suitable for "ditherable" or frequency-agile megnetrons.