Vacuum-tight window for microwave electron tube and travelling wave tube including this window

A vacuum-tight window for a microwave electron tube, said tube comprising, firstly, a zone under vacuum, form by a source of electrons, a focusing unit called a "delay line" and a collector of electrons and, secondly, at least one external transmission circuit through which a microwave signal interferes with the beam of electrons crossing said delay line, which is cylindrical, wherein said vacuum-tight window is cylindrical and is coaxial with a chamber which encases the delay line, and integrated with said chamber by brazing and wherein said window is made of ceramic material transparent to microwaves and further comprising a metallic flexible ring at each of the ends of said ceramic cylinder with a first ring being brazed to the chamber of the delay line and the second ring being brazed to at least one of said source and a collector sub-assembly coaxial with the delay line and wherein a microwave transmission antenna in the form of a metallic cylinder passes through the ceramic of the window with said antenna being formed by a metallic strip connected, at right angles, to said metallic cylinder which fits a clearance inserted in the chamber.