High frequency electron discharge device and focusing means therefor

Claim 1

A HIGH FREQUENCY TUBE WHICH COMPRISES AN ELONGATED, EVACUATED TUBULAR ENVELOPE, AN ELECTRON GUN ARRANGED TO PRODUCE AND DIRECT A BEAM OF ELECTRONS LONGITUDINALLY THERETHROUGH, AN INTERACTION STRUCTURE ARRANGED TO SUPPORT HIGH FREQUENCY FIELDS IN INTERACTING RELATION WITH SAID ELECTRON BEAM, MEANS FOR TRANSMITTING HIGH FREQUENCY ENERGY FROM SAID ENVELOPE ADJACENT ONE END OF SAID INTERACTION STRUCTURE, AND AT LEAST TWO BEAM FOCUSING STRUCTURES INTERCONNECTED THROUGH A LOW RELUCTANCE PATH AND SURROUNDING SAID ENVELOPE AND POSITIONED ON LONGITUDINALLY OPPOSITE SIDES OF SAID ENERGY TRANSMITTING MEANS, SAID FOCUSING STRUCTURES BEING ARRANGED TO CONJOINTLY PRODUCE SUBSTANTIALLY CONSTANT FOCUSING FORCES ON THE BEAM OF ELECTRONS WITHIN THE ENTIRE INTERACTION STRUCTURE, SAID FOCUSING STRUCTURES TOGETHER WITH SAID LOW RELUCTANCE PATH BEING ARRANGED TO PRODUCE MAGNETIC FIELDS WHICH ARE CHARACTERIZED BY AN ABSENCE OF TRANSVERSE COMPONENTS OF LUX IN THE VICINITY OF THE JUNCTURE BETWEEN SAID ENVELOP AND SAID ENERGY TRANSMITTING MEANS, SAID ONE OF SAID AT LEAST TWO BEAM FOCUSING STRUCTURES BEING A MAIN SOLENOID MEANS DISPOSED INTERNALLY OF THE LOW RELUCTANCE PATH AND EXTENDING ALONG SUBSTANTIALLY THE ENTIRE INTERACTION STRUCTURE, SAID OTHER OF SAID AT LEAST TWO BEAM FOCUSING STRUCTURES BEING AN AUXILIARY SOLENOID MEANS DISPOSED INTERNALLY OF THE LOW RELUCTANCE PATH, SAID LOW RELUCTANCE PATH HAVING A RE-ENTRANT PORTION WHICH EXTENDS WITHIN THE INTERIOR OF SAID AUXILIARY SOLENOID, SAID MAIN SOLENOID MEANS CONTRIBUTING TO THE MAGNETIC FIELD IN THE INTERIOR PORTION OF THE MAIN SOLENOID AND IN THE REGION OF THE JUNCTURE BETWEEN SAID ENVELOPE AND SAID ENERGY TRANSMITTING MEANS.