Abstract
Two types of secondary emitter materials, the rare earth oxides (RE2O3) doped Mo cermet cathodes and the Y2O3-W matrix pressed cathode, are introduced in this paper. According to the calculation results, Y2O3 exhibits the best secondary emission property among Y2O3, La2O3, CeO2 and Lu2O3. The rare earth oxides co-doped Mo cathodes in which Y2O3 is the main active substance exhibit better secondary emission property than single RE2O3 doped Mo cathode. The results obtained by the Monte-Carlo calculation method show that the secondary electron emission property is strongly related to the grain size of the cathode. The decreasing of the grain size reduces the positive charge effect of the rare earth oxide due to the electrons supplement from the metal to the rare earth oxide, whereby the secondary electrons are easier to escape into the vacuum. Y2O3 is introduced into Ba-W cathode to fabricate a pressed Y2O3-W matrix dispenser cathode. The result indicates that the secondary emission yield of the Ba-W cathode increases from 2.13 to 3.51 by adding Y2O3, and the thermionic emission current density (J 0) could reach 4.18 A/cm2 at 1050 °Cb.
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