Electron gun structure for producing an electron beam free of radial velocity components wherein the length of the first non-magnetic cylinder is approximately equal to an integral number of wave lengths of the scallop frequency

Claim 1

AN ELECTRODE SYSTEM FOR PRODUCING AND PROJECTING ALONG A PATH, EXTENDING COAXIALLY OF A HOMOGENEOUS UNIDIRECTIONAL MAGNETIC FIELD, AN ELECTRON BEAM HAVING NO SUBSTANTIAL RADIAL COMPONENT OF MOTION COMPRISING: A CATHODE; AN ANODE HAVING AN APERTURE CENTERED ON SAID PATH; MEANS FOR OPERATING SAID ANODE AT A POSITIVE POTENTIAL WITH RESPECT TO SAID CATHODE TO DRAW ELECTRONS THEREFROM INTO A BEAM HAVING AN INITIAL RADIUS DETERMINED BY SAID APERTURE, SAID BEAM, AS IT EMERGES FROM SID APERTURE, EXPANDS RADIALLY OUTWARDLY AND THIS PERTURBATION GIVES RISE TO A SINUSOIDAL COMPONENT OF RADIAL MOTION OF A PREDTERMINED SCALLOP FREQUENCY; MEANS, INCLUDING A CYLINDER OF NONMAGNETIC CONDUCTIVE MATERIAL POSITIONED COAXIALLY OF SAID PATH, FOR ESTABLISHING ABOUT SAID PATH A SUBSTANTIALLY ELECTRIC-FIELD-FREE DRIFT SPACE FOR SAID PERTURBED BEAM HAVING A LENGTH APPROXIMATELY EQUAL TO TAN INTEGAL NUMBER OF WAVE LENGTHS AT SAID SCALLOP FREQUENCY; AND MEANS FOR TERMINATING SAID DRIFT SPACE IN A CONVERGENT LENS WHICH HAS A PRINCIPAL PLANE LOCATED AT THE INTERCEPT OF SAID PERTURBED BEAM WITH AN EQUILIBRIUM RADIUS LARGER THAN SAID INITIAL RADIUS AND WHICH SUBJECTS SAID PERTURBED BEAM TO A RADIALLY INWARD FORCE TO CANCEL SAID COMPONENT OF RADIAL MOTION.