Zhiyuan Ren

Enhancement of secondary emission property of molybdenum cathode co-doped with La2O3 and Y2O3

Abstract La2O3 and Y2O3 co-doped Mo secondary emitters were prepared by three kinds of doping method combined with high temperature plasma sintering. The secondary electron emission property and microstructure of the cathodes were studied. It showed that the cathode prepared by liquid-liquid doping method exhibited the best emission property among all the samples prepared by liquid-solid doping, solid-solid doping and liquid-liquid doping methods due to a uniform distribution of different substances. RE2O3 existed uniformly at the grain boundaries and diffused to the cathode surface during a cathode activation period. A surface layer of RE2O3 formed after activation played an important role in the emission. The secondary emission yield of La2O3 and Y2O3 co-doped Mo prepared by liquid-liquid doping method was 4.34.

Emission property of Y2O3-doped Mo secondary emitter

Abstract Y2O3-doped Mo secondary emitters were prepared by liquid-liquid doping and solid-solid doping, respectively. The back-scattered scanning observation result indicates that the emitter prepared by liquid-liquid doping has fine microstructure whereas that prepared by solid-solid doping has large grain size. Y2O3-doped Mo emitter with small grain size prepared by liquid-liquid doping exhibits high emission property, i.e., the secondary electron yield can get to 5.24, about 1.7 times that prepared by solid-solid doping. Moreover, Y2O3-doped Mo emitter exhibits the best emission performance among La2O3-doped Mo, Y2O3-doped Mo, Gd2O3-doped Mo and Ce2O3-doped Mo emitters due to the largest penetration depth of primary electrons and escape depth of secondary electrons in this emitter. The secondary emission of the emitter with small grain size can be explained by reflection emission model and transmission emission model, whereas only transmission emission exists in the emitter with large grain size.

P1–30: Fabrication of Y 2 O 3 -Mo secondary electron emitters by air Plasma Spray method

Rare earth oxide (REO) doped Molybdenum metal ceramic emitters were successfully prepared by the air Plasma Spray (APS) method. Microstructure and secondary electron emission (SEE) performance were investigated. The relative uniform mixing of rare earth oxide and molybdenum have been observed. The maximum secondary electron yield is 3.3 after activation at 1100b(Mo brightness temperature) in vacuum.

Recent progress of rare earth oxide doped Molybdenum secondary electron emission cathodes

In this paper, the effect of different preparation process on the secondary electron emission performance was investigated. The different doping methods and preparation techniques such as Solid-Solid doping(SS), Liquid-Solid (LS) doping, Liquid-Liquid (LL) doping, Spark Plasma Sintering (SPS), Air Plasma Spray (APS) method, were introduced into this kind of materials. The microstructure of samples was observed with Hitachi S-3500N Scanning Electron Microscopy, equipped with Oxford Inca EDX equipment. The self-designed apparatus was used to evaluate secondary electron emission yields (δ) of samples in the ultra-high vacuum chamber. The secondary emission properties were measured at 600°C in order to avoid the influence of the thermionic emission.

Characterization of carburized La 2 O 3 doped Mo filament cathode

In this paper, the carburization method and the carburization mechanism have been studied in order to obtain the carburized La2O3 doped Mo filament cathode which could provide good emission property.

Secondary electron emission of Y{sub 2}O{sub 3}-Mo cermet cathode

Y{sub 2}O{sub 3}-Mo cermet cathodes were prepared by mechanical mixing of Y{sub 2}O{sub 3} and Mo powder. The prepared cermet cathode provides a certain secondary emission yield (3.09), about 1.8 times lower than that for the cathode prepared by sol-gel method. It was found that the cathode prepared by sol-gel method had a smaller grain size, which could be attributed to its higher emission property. The energy distributions of primary electrons in the cathodes with different grain sizes have been simulated by Monte Carlo method. Based on the calculation results, the emission models of the cathodes are established and presented. The cathodes with different grain sizes exhibited different ways of emission. Two types of emission, of reflection emission and transmission emission, existed in the cathode with small grain sizes whereas only transmission emission existed in the cathode with large grain sizes.

Investigation of Y 2 O 3 -Mo emitter

The emission property of Y<inf>2</inf>O<inf>3</inf>-Mo emitter depends on the contentration of Y<inf>2</inf>O<inf>3</inf>. Y<inf>2</inf>O<inf>3</inf>-Mo with 4wt% Y<inf>2</inf>O<inf>3</inf> could be used as a thermionic emitter and that with higher content of Y<inf>2</inf>O<inf>3</inf> (≫10wt%) could be served as a secondary emitter.