Electron beam generating system for high beam potentials

Claim 1

AN ELECTRON BEAM GENERATING SYSTEM FOR HIGH BEAM ACCELERATING VOLTAGES COMPRISING: A HOLLOW EVACUABLE CHAMBER HAVING SUPPORTED THEREIN AN ELECTRODE SYSTEM WHICH INCLUDES A CATHODE ASSEMBLY AND AN ANODE; SAID CATHODE ASSEMBLY INCLUDING A CATHODE, A CONTROL ELECTRODE MOUNTED ADJACENT THE CATHODE, AND SUPPORTING STRUCTURE SUPPORTING THE CONTROL ELECTRODE AND THE CATHODE IN THE CHAMBER; THE CATHODE ASSEMBLY CARRYING HIGH VOLTAGE WITH RESPECT TO GROUND POTENTIAL AND THE ANODE BEING HELD SUBSTANTIALLY AT GROUND POTENTIAL; SAID CHAMBER COMPRISING A HOLLOW INSULATING BODY FORMING AT LEAST A PART OF THE INTERIOR WALLS OF THE CHAMBER AND BEING COVERED ON ITS OUTER SURFACE WITH AN EARTHED ELECTRIC CONDUCTOR, THE DISTANCE BETWEEN THE EARTHED CONDUCTOR AND THE CATHODE ASSEMBLY BEING, AT LEAST IN SOME AREAS, SMALLER THAN THE INSULATING DISTANCE WHICH WOULD BE NECESSARY IN THE ABSENCE OF THE INSULATING BODY; THE MINIMUM THICKNESS OF THE INSULATING BODY BETWEEN THE CATHODE ASSEMBLY AND THE EARTHED CONDUCTOR BEING DETERMINED BY THE DIELECTRIC STRENGTH OF THE INSULATING MATERIAL OF WHICH THE INSULATING BODY IS MADE; SAID CHAMBER HAVING ITS AXIS SUBSTANTIALLY COINCIDING WITH THE AXIS OF THE BEAM TO BE GENERATED, THE CATHODE ASSEMBLY BEING SUPPORTED AT A PREDETERMINED AXIAL POSITION IN AN INNER CIRCUMFERENTIAL AREA OF THE CYLINDER AND THE ANODE HAVING A CENTRAL ANODE OPENING THROUGH WHICH THE GENERATED BEAM PASSES OUT OF THE CYLINDER; THE CATHODE ASSEMBLY AND THE ANODE BEING SPACED APART AND HAVING CENTRAL PORTIONS, RESPECTIVELY, DEFINING THEREBETWEEN AN ACCELERATION DISTANCE FOR THE ELECTRON BEAM GENERATED; THE INTERIOR SURFACE OF THE CHAMBER BEING SHAPED SO THAT THE SURFACE POTENTIALS CREATED THEREON BY THE CREEP CURRENT BETWEEN THE INNER CIRCUMFERENTIAL AREA WHERE THE CATHODE ASSEMBLY IS SUPPORTED AND THE ANODE SUBSTANTIALLY COINCIDE WITH THE POTENTIAL DISTRIBUTION GENERATED BY THE ELECTRIC FIELD BETWEEN THE CATHODE ASSEMBLY, THE ANODE AND THE EARTHED ELECTRIC CONDUCTOR COVERING ON THE OUTER SURFACE OF THE INSULATING BODY; AND SAID CHAMBER HAVING AN ACCESS OPENING NORMALLY CLOSED BY DETACHABLE CLOSURE MEANS COMPRISING A LID MADE OF INSULATING MATERIAL WITH AN OUTER CONDUCTING COVERING IN CONTACT WITH SAID EARTHED CONDUCTOR COVER WHEN THE LID IS IN POSITION CLOSING THE ACCESS OPENING.