The life of impregnated Ba-W cathodes with a new construction have been evaluated using an accelerated life test at three different temperatures (1170℃,1130℃,1090℃) and constant current density (2A/cm^2).According ...The life of impregnated Ba-W cathodes with a new construction have been evaluated using an accelerated life test at three different temperatures (1170℃,1130℃,1090℃) and constant current density (2A/cm^2).According to the relationship of life with operating temperatures,an accelerated equation has been set up.The cathode life at normal operating temperature is deducted based on the accelerated equation.The results show that life of the novel cathode exceeds 190,000 hour at a current density of 2A/cm^2.展开更多
In order to obtain higher emission performance than that of a traditional M-type cathode, we have developed a new type impregnated dispenser cathode. The new cathode is impregnated with a new active substance with mol...In order to obtain higher emission performance than that of a traditional M-type cathode, we have developed a new type impregnated dispenser cathode. The new cathode is impregnated with a new active substance with molar ratio of 26BaO·29SrO·8Sc2O3 ·7CaO·Al2O3 . This paper introduces the emission performance, surface active material, and work function of the new cathode. At 1100℃B , the DC current density and pulse current density are 30.6±1.0 A/cm2 and 171.6±2.8 A/cm2 , respectively, 2.1 and 5.4 times of that of an M-type cathode. The work function of the new cathode is 1.668± 0.002 eV. High concentration O-Al-Sc-Sr-Ba and O-Al-Sc-Ba are found in the pores and at pore edges, respectively. By comparing the emission performances and surface characteristics of as-polished and as-cleaned cathodes, it is proposed that, the emission around pore ends forms the major part of the total emission for the new cathodes.展开更多
A new type of dispenser cathode with dual-layer (Os-W/Re) is developed. The cathode coated with Os-W/Re shows better emission performance than the cathode coated with Os-W alloy. X-ray Photoelectron Spectroscopy (XPS)...A new type of dispenser cathode with dual-layer (Os-W/Re) is developed. The cathode coated with Os-W/Re shows better emission performance than the cathode coated with Os-W alloy. X-ray Photoelectron Spectroscopy (XPS) spectra demonstrate that ternary alloy coating (Os-W-Re) formed on the surface of the cathode with dual-layer (Os-W/Re) after full activation is the major reason why it has better emission than the cathode with Os-W alloy. The surface of each variety of the cathode is characterized with Scanning Electron Microscope (SEM) before and after activation: the emitting surface of the cathode with Os-W alloy after ageing appeared non-adherence (flaking) in localized areas, which is one of the reasons for non-uniform emission. However, the surface of the cathode with dual-layer (Os-W/Re) does not present film peeling under the same conditions. Thus it ensures better emission uniformity and functional reliability for the dispenser cathode.展开更多
A new kind of Ba-W dispenser cathode impregnated with barium ytterbate has been deve-loped.It has good properties;high coefficient of secondary emission,strong ability of resisting oxygenpoisoning,high thermionic emis...A new kind of Ba-W dispenser cathode impregnated with barium ytterbate has been deve-loped.It has good properties;high coefficient of secondary emission,strong ability of resisting oxygenpoisoning,high thermionic emission current density and more uniform emission on the cathode surface.The cathode is suitable for using as an electron emitter for microwave tubes,especially magnetrons.展开更多
The experimental results of studies of four kinds of cathode emitting intense electron beams are demonstrated under multi-pulsed mode based on an experimental setup including two multi-pulse high voltage sources.The t...The experimental results of studies of four kinds of cathode emitting intense electron beams are demonstrated under multi-pulsed mode based on an experimental setup including two multi-pulse high voltage sources.The tested cathodes include velvet,carbon fibers,carbon nano-tubes （CNTs） and dispenser cathodes.The results indicate that all four are able to emit multi-pulsed beams.For velvet,carbon fiber and CNTs,the electron induced cathode plasma emission may be the main process and this means that there are differences in beam parameters from pulse to pulse.For dispenser cathodes tested in the experiment,although there is a little difference from pulse to pulse for some reason,thermal-electric field emission may be the main process.展开更多
To study the formation of detrimental phases under the sulfur gas impurity to the long-term degradation in the cathode material,the classic cathode material,(La_(0.8)Sr_(0.2))_(0.95)MnO_(3)(LSM),was prepared,sintered,...To study the formation of detrimental phases under the sulfur gas impurity to the long-term degradation in the cathode material,the classic cathode material,(La_(0.8)Sr_(0.2))_(0.95)MnO_(3)(LSM),was prepared,sintered,and annealed at 800,900,and 1000℃ in the sulfur-containing atmospheres,respectively.Through X-ray diffraction,scanning electron microscope,and transmission electron microscopy techniques,as well as the computer coupling of phase diagrams and thermochemistry methodology,the secondary phases,especially the detrimental ones,under different conditions were predicted and experimentally verified correspondingly.Furthermore,sulfur poisoning results indicate that the accelerated tests might have degradation mechanisms different from actual operation conditions.More importantly,comprehensive comparisons among various impurity-containing conditions were also made to recommend better operation parameters.展开更多
A 2MeV thermionic cathode test stand was established to meet the requirement of the large area thermionic cathode system.A 100ram in diameter type'B'thermionic dispenser cathode was developed.A 1000A emission ...A 2MeV thermionic cathode test stand was established to meet the requirement of the large area thermionic cathode system.A 100ram in diameter type'B'thermionic dispenser cathode was developed.A 1000A emission current was produced at the voltage of the diode about 1.8MV,the pulse width about 90ns(FWHM),and the cathode temperature about 1350℃.The emission current density is 12A/cm^2.The results indicate that a large area thermionic cathode which produces high quality and high current electron beams is visible.The results also indicate that the ability of cathode emission relies on the diode-vacuum and cathode-temperature.展开更多
文摘The life of impregnated Ba-W cathodes with a new construction have been evaluated using an accelerated life test at three different temperatures (1170℃,1130℃,1090℃) and constant current density (2A/cm^2).According to the relationship of life with operating temperatures,an accelerated equation has been set up.The cathode life at normal operating temperature is deducted based on the accelerated equation.The results show that life of the novel cathode exceeds 190,000 hour at a current density of 2A/cm^2.
基金Supported by the National Natural Science Foundation of China (No. 60871053)the Major State Basic Research Development Program of China (No. 2013CB328901)
文摘In order to obtain higher emission performance than that of a traditional M-type cathode, we have developed a new type impregnated dispenser cathode. The new cathode is impregnated with a new active substance with molar ratio of 26BaO·29SrO·8Sc2O3 ·7CaO·Al2O3 . This paper introduces the emission performance, surface active material, and work function of the new cathode. At 1100℃B , the DC current density and pulse current density are 30.6±1.0 A/cm2 and 171.6±2.8 A/cm2 , respectively, 2.1 and 5.4 times of that of an M-type cathode. The work function of the new cathode is 1.668± 0.002 eV. High concentration O-Al-Sc-Sr-Ba and O-Al-Sc-Ba are found in the pores and at pore edges, respectively. By comparing the emission performances and surface characteristics of as-polished and as-cleaned cathodes, it is proposed that, the emission around pore ends forms the major part of the total emission for the new cathodes.
基金Supported by the National Science Fund for Distinguished Young Scholars of China (No.60125104).
文摘A new type of dispenser cathode with dual-layer (Os-W/Re) is developed. The cathode coated with Os-W/Re shows better emission performance than the cathode coated with Os-W alloy. X-ray Photoelectron Spectroscopy (XPS) spectra demonstrate that ternary alloy coating (Os-W-Re) formed on the surface of the cathode with dual-layer (Os-W/Re) after full activation is the major reason why it has better emission than the cathode with Os-W alloy. The surface of each variety of the cathode is characterized with Scanning Electron Microscope (SEM) before and after activation: the emitting surface of the cathode with Os-W alloy after ageing appeared non-adherence (flaking) in localized areas, which is one of the reasons for non-uniform emission. However, the surface of the cathode with dual-layer (Os-W/Re) does not present film peeling under the same conditions. Thus it ensures better emission uniformity and functional reliability for the dispenser cathode.
文摘A new kind of Ba-W dispenser cathode impregnated with barium ytterbate has been deve-loped.It has good properties;high coefficient of secondary emission,strong ability of resisting oxygenpoisoning,high thermionic emission current density and more uniform emission on the cathode surface.The cathode is suitable for using as an electron emitter for microwave tubes,especially magnetrons.
基金Supported by National Nature Science Foundation of China(10575090)State Key Laboratory of Advanced Materials (Beijing University of Science and Technology, 20082D-10)
文摘The experimental results of studies of four kinds of cathode emitting intense electron beams are demonstrated under multi-pulsed mode based on an experimental setup including two multi-pulse high voltage sources.The tested cathodes include velvet,carbon fibers,carbon nano-tubes （CNTs） and dispenser cathodes.The results indicate that all four are able to emit multi-pulsed beams.For velvet,carbon fiber and CNTs,the electron induced cathode plasma emission may be the main process and this means that there are differences in beam parameters from pulse to pulse.For dispenser cathodes tested in the experiment,although there is a little difference from pulse to pulse for some reason,thermal-electric field emission may be the main process.
文摘To study the formation of detrimental phases under the sulfur gas impurity to the long-term degradation in the cathode material,the classic cathode material,(La_(0.8)Sr_(0.2))_(0.95)MnO_(3)(LSM),was prepared,sintered,and annealed at 800,900,and 1000℃ in the sulfur-containing atmospheres,respectively.Through X-ray diffraction,scanning electron microscope,and transmission electron microscopy techniques,as well as the computer coupling of phase diagrams and thermochemistry methodology,the secondary phases,especially the detrimental ones,under different conditions were predicted and experimentally verified correspondingly.Furthermore,sulfur poisoning results indicate that the accelerated tests might have degradation mechanisms different from actual operation conditions.More importantly,comprehensive comparisons among various impurity-containing conditions were also made to recommend better operation parameters.
文摘A 2MeV thermionic cathode test stand was established to meet the requirement of the large area thermionic cathode system.A 100ram in diameter type'B'thermionic dispenser cathode was developed.A 1000A emission current was produced at the voltage of the diode about 1.8MV,the pulse width about 90ns(FWHM),and the cathode temperature about 1350℃.The emission current density is 12A/cm^2.The results indicate that a large area thermionic cathode which produces high quality and high current electron beams is visible.The results also indicate that the ability of cathode emission relies on the diode-vacuum and cathode-temperature.
