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During the activation and ageing,the evaporation components and rates from 4.56:1.44:2impregnated dispenser cathode have been determined by the vapor-collect method based on the Augerelectron spectroscopy(AES).(1)The evaporation rate of a cathode after ageing differs from that of a justactivated cathode by a factor of 5 to 10.The evaporation energy of the former is 4.58 eV,and that of the latter is4.34 eV.(2)At operating temperature,the metallic barium in the evaporated materials is about 90%,and thebarium oxide is about 9.3%.(3)Blow 1000℃ the evaporation of Ca is not significant;over 1150℃ the Ca startsevaporating rapidly,particularly in the activation process,it may approach 3.5% at 1250℃.
During the activation and aging, the evaporation components and rates from 4.56: 1.44: 2 impregnated dispenser cathode have been determined by the vapor-collect method based on the Augerelectron spectroscopy (AES). (1) The evaporation rate of a cathode after ageing differs from that of a just activated cathode by a factor of 5 to 10. The evaporation energy of the former is 4.58 eV, and that of the latter is 4.34 eV. (2) At operating temperature, the metallic barium in the evaporated material is about 90 %, and the barium oxide is about 9.3%. (3) Blow 1000 ° C the evaporation of Ca is not significant; over 1150 ° C the Ca startseva charging rapidly, particularly in the activation process, it may approach 3.5% at 1250 ° C.