科研之友
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摘要
Developing new active substance composition system and its preparation method to enhance scandate cathode's emission property is a hotspot in the research field of thermionic cathode especially high-emission cathode. A novel highly active impregnant substance consisting of polymetallic oxide which apparently increases scandium's appending proportion and greatly enhances cathode's emission current density is put forward in this paper. Freeze-drying method is applied into preparation of the active substance's precursor and effectively solves the problem of inhomogeneity and uncontrollability in the mechanical crushing, grinding and mixing procedures of conventional solid-phase synthesis routine. Cathode which adopted novel composition system and substance acquired by new preparation routine reaches a pulse emission current density of above 500 A/cm2 under close-spaced diode configuration and 218.5 A/cm2 in an electron gun. Under the DC diode experimental configuration, the cathodes' emission lifetime test has endured for 10500 hours with no emission current drop; while in the electron gun with a pulse drive of heavy duty cycle (5%), the cathode maintains a big workload of more than 50 A/cm2 after having worked for 2010 hours. Via Deep UltraViolet laser-Photo Emission and Thermal Emission Electron Microscopy (DUV-PEEM/TEEM) analyzation, the phenomenon ofthermionic emission points' amount increases and emitting micro-area expands on the newly prepared high-emission cathode's surface is observed. Finally, a 'binary tree' emission model is brought up, hoping to explain the physical mechanism of scandate cathode's high emission character with new active substance.
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