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Two types of secondary emitter materials, the rare earth oxides(RE_2O_3) doped Mo cermet cathodes and the Y_2O_3-W matrix pressed cathode, are introduced in this paper. According to the calculation results, Y_2O_3 exhibits the best secondary emission property among Y_2O_3,La_2O_3,CeO_2 and Lu_2O_3. The rare earth oxides co-doped Mo cathodes in which Y_2O_3 is the main active substance exhibit better secondary emission property than single RE_2O_3 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. Y_2O_3 is introduced into Ba-W cathode to fabricate a pressed Y_2O_3-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 Y_2O_3, and the thermionic emission current density(J_0) could reach 4.18 A/cm~2 at 1050 ℃b.
Two types of secondary emitter materials, the rare earth oxides (RE 2 O 3) doped Mo cermet cathodes and the Y 2 O 3 -W matrix pressed cathode, are presented in this paper. According to the calculation results, Y 2 O 3 exhibits the best secondary emission properties among Y 2 O 3, La 2 O 3 The rare earth oxides co-doped Mo cathodes in which Y 2 O 3 is the main active substance exhibit better secondary emission property than single RE 2 O 3 doped Mo cathode. The results obtained by the Monte-Carlo calculation method show that the secondary electron emission 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. Y_2O_3 is introduced into Ba-W cathode to fabricate a pressed Y_2O_3-W matrix dispenser cathode. The result indicates that the second ary emission yield of the Ba-W cathode increases from 2.13 to 3.51 by adding Y_2O_3, and the thermionic emission current density (J_0) could reach 4.18 A / cm ~ 2 at 1050 ° C b.