Traveling wave tube incorporating an electrostatic focusing arrangement comprising a meander line slow wave structure and two further electrodes co-extensive therewith

Claim 1

A TRAVELLING WAVE TUBE HAVING AN EVACUATED ENVELOPE WITHIN WHICH ARE DISPOSED: A SLOW WAVE STRUCTURE IN THE FORM OF A SINGLE ELONGATED CONDUCTOR WHICH IS SHAPED SO AS TO PROVIDE A PAIR OF PERIODIC METAL STRUCTURES WHOSE METAL ELEMENTS ARE CONSTITUTED BY SECTIONS OF SAID CONDUCTOR, THE PERIODIC STRUCTURES BEING DISPOSED WITH THEIR LENGTHS, SUBSTANTIALLY PARALLEL TO EACH OTHER, BEING SEPARATED BY A LINEARLY CLEAR SPACE ALONG WHICH AN ELECTRON BEAM MAY TRAVEL SO AS TO INTERACT WITH AN ELECTROMAGNETIC WAVE PROPAGATED ALONG THE SLOW WAVE STRUCTURE AND BEING DISPOSED SO THAT THE GAPS IN EACH PERIODIC STRUCTURE ARE OPPOSITE THE ELEMENTS OF THE OTHER PERIODIC STRUCTURE, THE CONDUCTOR BEING FOLDED SO THAT SAID ELEMENTS ARE JOINED TOGETHER END TO END IN A SEQUENCE, ALTERNATING BETWEEN THE TWO PERIODIC STRUCTURES, WHICH IS THE SAME AS THE SEQUENCE IN WHICH THE ELEMENTS ARE ARRAYED ALONG THE LENGTH OF SAID SPACE AND THE CONDUCTOR BEING SHAPED SO THAT AT LEAST THE MAJOR PARTS OF ALL SAID ELEMENTS ARE SUBSTANTIALLY RECTILINEAR AND PARALLEL TO EACH OTHER; AND MEANS FOR PROJECTING AN ELECTRON BEAM LONGITUDINALLY INTO SAID SPACE AT ONE END, THE SLOW WAVE STRUCTURE FORMING PART OF AN ELECTROSTATIC FOCUSSING DEVICE FOR THE ELECTRON BEAM WHICH ALSO INCLUDES TWO FURTHER METAL STRUCTURES WHICH ARE ELECTRICALLY INSULATED FROM THE SLOW WAVE STRUCTURE AND WHICH EXTEND RESPECTIVELY ON EITHER SIDE OF THE SLOW WAVE STRUCTURE SO THAT EACH PERIODIC STRUCTURE LIES BETWEEN THE OTHER PERIODIC STRUCTURE AND ONE OF THE FURTHER METAL STRUCTURES, WHEREBY IN OPERATION, WITH SUITABLE ELECTROSTATIC POTENTIALS APPLIED TO THE SLOW WAVE STRUCTURE AND THE FURTHER METAL STRUCTURES SUCH THAT THE FURTHER METAL STRUCTURES ARE NEGATIVE WITH RESPECT TO THE SLOW WAVE STRUCTURE, THE ELECTRON BEAM IS CONSTRAINED TO TRAVEL ALONG SAID SPACE WITH AN UNDULATORY MOTION SUCH THAT IT APPROACHES THE TWO PERIODIC STRUCTURES IN TURN; AND THE TUBE FURTHER INCLUDING RADIO FREQUENCY INPUT AND OUTPUT CONNECTORS RESPECTIVELY COUPLED TO THOSE ENDS OF THE SLOW WAVE STRUCTURE ADJACENT AND REMOTE FROM SAID ONE END OF SAID SPACE.