Experiment And Simulation Research Of Cathode With Low Vaporization And High Current Density

Vacuum electric devices are the indispensable component of modern military facilities,industrial manufacturing and high tech research,which play an significant role in various regions.As the heart of Vacuum electric devices,cathodes supply the essential electron source,directly influencing its characteristics and life.And the thermionic cathodes are applied to the Vacuum electric devices most widely.To meet the demand of future devices,thermionic cathode with low vaporization and high current density is chosen as the research object in this paper and planned to modify its surface.Firstly,surface modification of dispenser cathode is performed in this paper and scanning electron microscope is used to study the component and microscopic morphology of surface.The emission current density of experimental cathode is obtained more than 25A/cm² at the temperature of 1050 after complete activation,which meets the level of most aluminate dispenser cathode.This means M type cathodes has the potentials to obtain high current density.Meanwhile,the evaporation rate of cathode reach 8.14×10;¹¹g/cm²·s at the temperature of 1000.SEM pictures show that the coating of cathode contains good consistency before and after activation,ensuring the uniformity of emission.EDS pictures reveal that the components of surface are stable,and alloy layer with stable structure is formed between coating and matrix.Secondly,this paper aims at establishing a theoretical model of the cathode surface structure,investigating the work function,formation energy and the electronic properties of the microstructure and giving a further explanation of the emission mechanism of the M type cathodes.The work function trend of cathode surface structure with Ba coverage is also analysed in this paper.When Ba coverage is0.25ML,the?100?plane of W-Os-Ru alloy structure obtains minimum work function of 1.514eV,but this structure is unstable.The stability of the structure decreases first and then increase with the increase of Ba coverage.