GB787290A - Improvements in or relating to high-frequency electron arrangements - Google Patents

Abstract

787,290. Magnets. SIEMENS & HALSKE AKT.-GES. Sept. 21, 1955 [Sept. 21, 1954],No. 26983/55. Class 35. [Also in Group XL (a)] Travelling wave or other high-frequency electron tube apparatus comprises magnetic focusing means consisting of one or more permanent magnets, e.g. a single tubular magnet or a plurality of bar magnets 4, 5, Fig. 3, or 19 . . . 26, Fig. 4B, wherein a flux guide is widened at at least the end of the tube surrounding the gun and the cross-section of the narrow part of the guide tube, Fig. 3, and/or that of a shunting guide tube 18, Fig. 4B, is progressively reduced from the junction between the wider and narrower parts of the guide tube either continuously or in small steps. The resulting increase in field along the narrow part of the guide tube away from the stepped portion counteracts the normal decrease in field in this direction due to the diverging lines of force and ensures that the resultant field is uniform or increases towards this end of the guide tube. In one form, Fig. 3, the cross-section of the guide tube 1 tapers from the stepped portion towards the collector end 16, the angle of taper being up to 10 degrees. The gun has welmelt 13 and focusing electrodes 14, 15, and the delay line is a helix 12. In another embodiment, Fig. 4B, the guide tube 17 is of constant wall thickness but a second guide tube 18 has a wall of tapering thickness and can be slotted as shown.