GB1280960A - Mode suppression means for a clover-leaf slow wave circuit - Google Patents

Abstract

1280960 Travelling-wave tubes VARIAN ASSOCIATES 26 Oct 1970 [31 Oct 1969] 50830/70 Heading H1D Band-edge oscillations in a clover-leaf slowwave structure having eight radial coupling slots 22 and four projecting conductive nose portions 23 in each cavity are damped by modesuppression cavity resonators 27 which are housed at least partly in the nose portions 23, and which communicate with the slow-wave structure cavities 21 through slots 28. As shown, each of the nose portions 23, which are rotationally displaced in successive adjacent slow-wave structure cavities 21 by 45 degrees, houses a mode suppression cavity 27, the four cavities 27 coupled to each cavity 21 being tuned near to the mode frequency of the slowwave circuit, and the coupling slots 28 having a length near to a half wavelength for this frequency. The walls of cavities 27 are coated with an Al/Cr/Co/Fe lossy material, as also may the walls of the cavities 21. The cavities 27 are kept sufficiently small to permit their being housed within the tube envelope 13 by the use of capacitive posts 29 which project from one side wall of the cavity towards the other, leaving a space 31 therebetween, the choice of which permits the cavities 27 to be stagger-tuned about the # mode frequency. As described, the cloverleaf circuit is incorporated in a travelling-wave tube which includes an initial section of slowwave structure formed by a plurality of staggertuned cavities.