STRUCTURE DE GUIDE D'ONDES HELICOIDALE POUR UN TUBE A ONDES PROGRESSIVES ET SON PROCEDE DE FABRICATION

L'INVENTION CONCERNE UNE STRUCTURE DE GUIDE D'ONDES HELICOIDALE POUR UN TUBE A ONDES PROGRESSIVES ET SON PROCEDE DE FABRICATION.UNE STRUCTURE A ONDES LENTES 50 SELON L'INVENTION COMPORTE UN FILET HELICOIDAL 12 DIRIGE RADIALEMENT CENTRE SUR UN AXE 15, AVEC UNE OUVERTURE CENTRALE 34 SUR TOUTE SA LONGUEUR, ET PAR LAQUELLE PASSE UN FAISCEAU D'ELECTRONS 14. UN MANCHON EXTERIEUR 38 EST BRASE SUR LA PERIPHERIE EXTERIEURE DU FILET DE MANIERE A FORMER UN GUIDE D'ONDES HELICOIDAL AUTOUR DE L'AXE DE LA STRUCTURE A ONDES LENTES.L'INVENTION S'APPLIQUE NOTAMMENT A DES TUBES A ONDES PROGRESSIVES FONCTIONNANT A DES FREQUENCES DE L'ORDRE DE 20 A 30 GIGAHERTZ. A waveguide helical slow-wave structure is formed of a solid rod of copper machined with a deep, narrow helical groove. A copper sleeve is brazed to the periphery of the resulting helical thread to form a helically spiraling pathway about a solid axially centered and axially extending center portion. The center portion is then partially eroded away to form a slow wave structure having a helical radially-extending portion with an inner helical axially-extending ridge to provide a helical axially-centered gap between adjacent ridges. The slow wave structure contains the microwave energy which follows the spiral path of the structure and produces RF voltage across the gap of adjacent portions of the ridges to thereby form a gapped-wall surrounding an axially-extending hole for gap electric field interaction with the axial electron beam of a traveling wave tube of which the slow wave structure is a part.