GB1366742A - Travelling wave tube - Google Patents

Abstract

1366742 Travelling-wave tubes THOMSONCSF 25 Sept 1972 [28 Sept 1971] 44245/72 Heading H1D A dual mode travelling-wave amplifier capable of operating either in a continuous low-power mode, or in a high-power pulsed mode, includes an electron source producing either a first electron beam or, simultaneously, both the first beam and a second, coaxial beam propagating in the same direction but with a different velocity; a first slow-wave structure capable of interacting with the first beam; a second slowwave structure, connected to the first through a matching section, capable of interacting with the second beam; and an output coupled to the second structure and producing the amplified signal resulting from the interaction between the first beam and the first structure, or by the latter interaction together with interaction between the second beam and the second structure. As shown, a first electron gun 1 has an annular cathode 11, an anode 12, and a modulating electrode 13, while a second gun 2, producing a coaxial pencil beam, has a disc cathode 21, anode 22, modulating electrode 23, and blocking grid 24. The first slow-wave structure 5 is a severed helix, and is connected via the matching section 7 to a second helix 6, of lower delay factor. The beam from the cathode 11 has a velocity producing interaction with the structure 5, the structure 6 passively transferring the resulting amplified signal to the tube output 60, this signal constituting the output for the first mode. In the second mode, a pulsed beam from cathode 21 is additionally produced, by use of grid 24, for interaction with the structure 6. A polepiece (3, Fig. 2, not shown) and magnetic screen (4) ensure focusing of the two beams.