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In this paper, operation process of scandia-doped dispenser cathodes is studied based on surface behavior, evaporation and emission properties during preparation, activation, operation and life duration.
In vacuum system, area source electron gun emits electrons to bombard the standard screen. With the first anode and the second anode in different potentials, the images show the features of divergent, uniform, convergence and submerge. Photos, images acquired by brightness meter, and the image gray values are listed in Table 1. By image gray value analysis, it can be seen that in item no. 1, the electrons...
Model scandate thermionic cathodes have been prepared by rf reactive sputtering of scandium oxide and barium oxide onto tungsten foil. By preparing separate, 200 nm thick layers of these oxides, sputtered through different sized masks, the function of barium oxide and scandium oxide can be identified directly in the thermionic electron emission image. Scandium oxide is sputtered through a 100 micron...
In this paper we propose measurement system for non-destructive quality control of wide class thermionic cathodes in different electron-optical systems.The devices with different electron-optical systems and with thermionic cathodes which operate in different regime have significant differences in output parameters.
Scandate cathode exhibits the highest emission property among all the thermionic cathodes. Scanadia Doped Dispenser cathode (SDD cathode) is one of the promising cathodes due to its good emission property and reproducibility. The impacts of local electric field enhancement on emission capability of cathode have be considered by applying the actions of Schottky effect and electric field on semiconductor...
In the present paper, noise diagnostic problems of thermionic cathodes in electrovacuum devices is presented and propose to use different features of fluctuation noise as a potential diagnostic tool. The most attention has been concentrated on flicker and relax type components. These components are most sensitive to the physics processes on the emitting surface of cathodes.
In the present paper, the influencing factors of heater-cathode assembly's temperature are discussed. In order to searching the reasons of heater-cathode assembly's temperature waving, some elements are discussed from the consistency of supporting balloon, sintered batches of heater assembly and gap of heater-cathode assembly.
Summary form only given. Tungsten cathodes doped with Y, La and Ce has better thermionic electron emission properties than thoria tungsten. Its fabrication technology has hampered its application. In this paper, its preparation technology was investigated and its role on the preparation process was discussed. Results showed that the doping process was very important for the cathode fabrication as...
In this paper, a study on quick spark plasma sintering (SPS) method for synthesizing the polycrystalline CeB<;sub>6<;/sub> bulk is presented. CeB<;sub>6<;/sub> is the material of choice for high current density cathode. However, in fact, because of the long sintering time and high temperature, the traditional hot pressure sintering preparation of polycrystalline CeB<;sub>6<;/sub>...
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