Patent GB-873586-A (GB)
Title: Improvements in or relating to travelling wave tubes
IPC: H01J23/24
Filed: 1959-06-15
Abstract: 873,586. Travelling wave tubes. SIEMENS & HALSKE A. G. June 15, 1959 [June 16, 1958], No. 20417/59. Class 39(1). A travelling wave tube includes as a delay line a plurality of pairs of baffle plates stacked longitudinally along the tube, each pair of baffle plates being constituted by a first and a second baffle plate in mutual contact, each of the first baffle plates has a central aperature and n other apertures disposed symmetrically with respect to and equidistantly from the central aperture, the first baffle plates being arranged so that corresponding ones of the other apertures have common axes therethrough and are in register, each of the second baffle plates has a central aperture and is in the form of a regular polygon with n/2 sides in each of which there are two recesses, each of the second baffle plates being arranged so that its central aperture is in register with the' central aperture of the first baffle plates and each recess is in register with a corresponding series of said other apertures, succeeding ones of the second baffle plates being angularly displaced relatively to each other by an angle of 360/n, each of the recesses being bridged by means intersecting a correspond-' ing one of said axes. The bridging means are wires. The outer sets of apertures are all in alignment and serve as delay lines operating as forward wave travelling wave tubes and the central apertures also in alignment serve as a delay line operating as a backward wave oscillator which may preferably feed energy to the outer delay lines operating as forward wave amplifiers, for example by circumferential notches in a 'wheel' electrode 13 (multi-apertured for passage of a plurality of circumferential electron beams through the sets of circumferential apertures in the baffle plates) and the outputs are directed into a common waveguide 5 by means of conical shaping of the collector and of block 3 to define a convergent passage from outer delay lines to waveguide 5 which feeds energy through ceramic window 4. The conical collector has peripherical notches 26 to assist the impedance matching. There are two electron guns 6 and 8, gun 6 generating an annular electron beam to supply the delay lines 12 and gun 8 supplying a solid cylindrical electron beam to central delay line 12. After the stamped or cut sheet baffle plates have been stacked in position and soldered together the wires 16, 17 to form the bridges are wound preferably under tension in the recesses in baffle plates 19 and soldered to 14, 19. The central delay line 12 also has bridges formed by 2 rods disposed at 180 degrees intervals adjacent ones of which are relatively displaced by 90 degrees and which have central apertures for the electron beam. The angle between wires and rods of successive intermediate baffle plates may be such that the dispersion curves of 11, 12 are altered so as to make the delay lines 11, 12 dispersionless for the backward wave fundamental and forward wave spatial harmonic, e.g. 10-50 degrees, 45 degrees in Fig. 3 for the outer and 90 degrees for the inner sets of apertures. The tube is used as a forward wave amplifier. Apertures 18 can be used for input and output coupling if delay lines 11 operate as forward wave amplifiers or backward wave oscillators. In the latter case the conical transition section to the output guide is at the gun end of the tube. It is stated that delay lines 11, 12 both have a backward wave fundamental and a forward wave spatial harmonic. In modifications the baffle plates 19 may be equilaterial triangles or polygons of 5, 6, or 7 or more sides. In a modified embodiment the central delay line Fig. 4a is interdigitated the interdigitated tongues thereof having apertures for the passage of the electron beam. A slot is cut in baffle plates 14, Fig. 3a, and 21, Fig. 4a, where the wires 16, 17 are to pass from one plate 19, Fig. 3b or 24, Fig. 4b (not shown), to the next plate 19 or 24. The baffle plates are produced by stamping or photoetching.