GB685752A - Travelling wave amplifier apparatus - Google Patents

Abstract

685,752. Travelling-wave tubes. WALLAUSCHEK, R. April 6, 1948 [April 15, 1947], No. 9671/48. Class 39(i) [Also in Group XL(b)] In a travelling wave amplifier apparatus the wave transmission path comprises a cylindrical dielectric tube coated on its exterior surface with a conductive layer and enclosing a conductive helix along the axis of which the beam passes, and the arrangement is such that the wave and beam velocities are substantially equal. In one form, Fig. 2, the whole inner and outer surfaces of the dielectric tube A are metallized and a screw tap P is then inserted to remove all the metal from the inner wall except for the desired helix. In another form, Fig. 3a, a helical groove is formed in the inner wall of the dielectric tube D, the whole surface is metallized as shown, and the inner wall is then reamed so as to leave only the desired helix, Fig. 3b (not shown). In another form, Fig. 4, the helix H is applied on the outer surface of a dielectric tube T1 through which the electron beam passes, and the outer metal layer is formed on the outer surface of a second dielectric tube T2. In all cases the dielectric material may be ceramic with a dielectric constant of about 100, and may have conductive material dispersed therein to attenuate the reflected wave to the desired degree. The attenuation may be varied so that it is a maximum at the input end and a minimum at the output end. The dielectric tube may constitute part of the vacuum-tight envelope of the device. The Specification as open to inspection under Sect. 91, states that in Fig. 4 the inner surface of tube T1 collects some electrons and so becomes negatively charged, so that it can serve as an additional focusing means. This subject-matter does not appear in the Specification as accepted.