FEASIBILITY STUDY OF NEW HIGH CURRENT DENSITY ELECTRON EMITTERS USING PULSE LASER OF ELECTRON BEAM IRRADIATION

CATHODES CAPABLE OF GENERATING CURRENTS OF 100 A TO 10,000 A WITH CURRENT DENSITIES OF 100 TO 1000 A/CM2 WITH HIGH BRIGHTNESS ARE REQUIRED FOR SUPERPOWER MICROWAVE, MM-WAVE AND OPTICAL COHERENT RADIATION SOURCES, SUCH AS FREE ELECTRON LASERS. OF PRESENTLY AVAILABLE CATHODES, ONLY FIELD EMISSION TYPE CATHODES CAN PRODUCE THE REQUIRED CURRENT DENSITIES. THESE ARE NOT SUITABLE FOR LONG PULSE OF HIGH DUTY CYCLE OPERATION, WHICH IS CRITICAL TO MANY APPLICATIONS. PULSE LASER DRIVEN PHOTOEMISSIVE AND PULSE HEATED THERMIONIC CATHODES HAVE RECENTLY BEEN SHOWN TO BE CAPABLE OF PRODUCING BEAMS WITH CURRENT DENSITIES EXCEEDING 100 A/CM(2) OVER 1 CM(2), AND WITH NORMALIZED BRIGHTNESSES AS HIGH AS 10(7) A/CM(2) RAD(2). CALCULATIONS INDICATE THAT WITH NEW METHODS OF COOLING, DUTY FACTORS AS HIGH AS 0.1 CAN BE ACHIEVED. IN ADDITION, WITH THESE CATHODES, EMISSION GATING IS POSSIBLE. THE PROPOSED WORK IS TO EXAMINE ANALYTICALLY IN DETAIL THE FEASIBILITY OF HIGH CURRENT DENSITY PHOTOEMISSIVE AND/OR PULSE HEATED THERMIONIC CATHODES SUITABLE FOR HIGH POWER MICROWAVE TUBES, INCLUDING OPTIMIZATION OF THE USE OF PRESENTLY KNOWN EMITTERS AS WELL AS A SEARCH FOR NEW MATERIALS.