Improvements in or relating to electron discharge devices

880,522. Discharge tubes. ELECTRIC & MUSICAL INDUSTRIES Ltd. Feb. 5, 1958 [Feb. 5, 1957], No. 3880/57. Class 39(1) An electron discharge device comprises a ceramic envelope part provided with a plurality of thickened portions which project inwardly to form longitudinally disposed ribs against which an electrode is supported so as to be free from vibration during operation of the device. In the reflex klystron shown, reflector electrode 9 and focussing electrode 11 engage ribs 15 formed on ceramic envelope parts 1 and 3 and are preferably secured thereto by brazing. Grids 7, 8 are supported by copper discs 13, 14 which form walls of resonator cavity 6, and which are sealed between the metallized ends of envelope parts 1, 2, 3 alignment of parts 1 and 3 being ensured by the use of appropriate mandrels or clamps. Accurate spacing of the electrodes is obtained by grinding envelope parts 1, 2 and 3 to the required lengths. To ensure good evacuation of the device, electrodes 9 and 11 may be provided with suitable apertures. Longitudinal ribs provided in an envelope in accordance with the invention may also be used to support the delay line, e.g. a helical conductor, of a travelling-wave tube.