X-ray tube with adjustable electron beam cross-section

Claim 1

AN X-RAY GENERATOR COMPRISING: AN ELECTRON GUN FOR PROJECTING AN ELECTRON BEAM ALONG A GIVEN PATH INCLUDING AN ELECTRON EMISSIVE CATHODE LOCATED COAXIALLY OF SAID PATH AND A HEATER FOR SAID CATHODE; AN ANODE STRUCTURE HAVING A CONDUCTIVE CYLINDRICAL PORTION POSITIONED AXIALLY OF SAID PATH AND SPACED FROM SAID CATHODE, HAVING AN OPEN END FACING SAID CATHODE, SAID CYLINDRICAL PORTION HAVING A RADIUS SMALL COMPARED TO THAT OF SAID CATHODE AND SUPPORTING AT ITS END REMOTE FROM SAID CATHODE A TARGET PORTION, CONSTRUCTED OF A MATERIAL WHICH RADIATES X-RAYS IN RESPONSE TO ELECTRON BOMBARDMENT, DISPOSED ACROSS SAID PATH; MEANS FOR ESTABLISHING A FOSUCING FIELD IN THE REGION BETWEEN SAID CATHODE AND SAID CYLINDRICAL PORTION TO FORM ELECTRONS EMITTED FROM SAID CATHODE SURFACE INTO A CONVERGING BEAM OF SUBSTANTIALLY CIRCULAR CROSS SECTION FOCUSED ON SAID TARGET AND FOR ESTABLISHING SAID CYLINDRICAL PORTION AND SAID TARGET AT APPROXIMATELY THE SAME OPERATION POTENTIAL, THE SPACING OF SAID TARGET FROM SAID OPEN END OF SAID CYLINDRICAL PORTION BEING GREATER THAN THE DEPTH OF PENETRATION OF SAID FOCUSING FIELD INTO SAID ANODE CYLINDER; AND ADJUSTABLE MAGNETIC MEANS SUPPORTED EXTERNALLY OF SAID ANODE CYLINDER FOR ESTABLISHING A MAGNETIC BEAM SHAPING FIELD ABOUT THE BEAM PATH TO SELECTIVELY SHAPE SAID BEAM INTO ANY OF A PLURALITY OF PREDETERMINED DIFFERENT NON-CIRCULAR BEAM CROSS SECTIONS AT SAID TARGET.