Advances in Thermionic Cathode of Tungsten and Molybdenum

Several kinds of tungsten thermonic cathodes have been introduced. As a promising alternative for thoriated tungsten, rare earth doped molybdenum cathode has been studied. Compared with the traditional thoriated tungsten, La- Mo cathode has higher emission current density at lower temperature, but it has poor emission stability. In order to im- prove the emission stability, systematical Study on the emission mechanism of La-Mo cathode has been carried out. The life of La-Mo cathode has been improved and has achieved 1400 h, which exceeds the minimum life for practical uses (1000 h). As another alternative for thoriated tungsten cathode, Y-Mo cathode has shown better performance. The ther- mionic emission capability of Y-Mo cathode is between that of La-Mo cathode and Th-W cathode.