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Study on Evaporation Properties of Impregnated Barium-Strontium Tungsten Cathode
Pages: 1215-1219
Year: Issue:  11
Journal: Vacuum Science and Technology

Keyword:  Barium-strontium tungstateEvaporation rateTime of flight mass spectroscopeQuartz crystal oscillation;
Abstract: The activation and thermal evaporation behavior of the impregnated barium-strontium tungstate cathode( uncoated) were investigated with time of flight mass spectroscope and quartz oscillator to understand the possible mechanisms responsible for the enhancement of emission intensity and increase of life-time. The impact of the activation temperature and pressure on the evaporation rate and contents of the evaporated materials was evaluated.The results show that the high temperature significantly affects the activation and evaporate rate of the cathode. To be specific,starting at 1015℃,the evaporate rates of Ba and Ba O increased slowly,shooting up at 1120℃,possibly because of the surface segregation and oxidation of Ba. The impregnated Ba-Sr-W cathode can be fully activated at1100℃,with an average evaporation rate 50% lower than that of the conventional uncoated aluminate cathode.
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