Thermionic Electron Emission Stability of Mo-La_2O_3 Cathode

摘要

The carbonizing process and its influence on the thermionic electron emission properties of Mo-La_2O_3 cathode materials were investigated. The carbonized temperature, carbonized time and the pressure of C_6H_6 are key factors of the carbonizing process. The carbonized ratio, of Mo-La_2O_3 cathode increases with the increase of carbonizing temperature at low temperature. The highest carbonized ratio is 19.7 percent obtained at 1723 K, then the carbonized ratio decreases rapidly if temperature increases further. The carbonized ratio increases with the prolongation of carbonizing time during the process of first 6 min., after that the carbonization ratio changes little with the time increase, and the carbonized ratio increases with the increase of the C_6H_6 pressure when the pressure is low, the maximum carbonized ratio reaches 19.7 percent at 1.5X 10~(-2) Pa, then the carbonized ratio goes down sharply when the C_6H_6 pressure is over 1.5 X 10~(-2) Pa. The emission properties at different operated temperatures and the emission current stability of FU-6051 tubes equipped with Mo-La_2O_3 cathodes were also studied in the article. The study results indicate that the emission can keep stable only when the operating temperature is from 1700 to 1800 K and the carbonized layer must be composed by Mo_2C only. The FU-6051 tubes equipped with Mo-La_2O_3 cathodes have excellent stable emission current and the lifetime exceeds 3000 h when the cathode's carbonized ratio is 19.7 percent operated at 1773 K.