复铼膜阴极的发射和表面特性

本文报道了复铼膜扩散阴极的发射和表面特性的研究结果,并与S-型阴极进行了比较。实验结果表明:S-型阴极复铼膜后,其热电子发射明显提高,且分布均匀。月极表面上主要元素的俄歇像显示Ba在复铼膜阴极表面上的分布要比在S-型阴极表面上均匀得多,Ba的低能Auger谱和XPS的研究表明:与S-型阴极相比Ba在复铼膜阴极表面上呈现更强的金属特性。这可能是S-型阴极复铼膜后发射增大的主要原因。     

A NEW Ba-W DISPENSER CATHODE IMPREGNATED WITH BARIUM YTTERBATE

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.     

氧化钪掺杂钨基扩散阴极的结构、表面与发射特性的研究

以钪盐的水溶液与氧化钨液-固掺杂法制备了氧化钪掺杂钨基扩散阴极，利用扫描电镜、能谱分析仪和原位俄歇电子谱仪等现代分析技术研究了烧结体的形貌、Sc的分布及阴极的表面特性。用自行研制的微机控制全自动电子发射测量装置检测了阴极发射性能。研究表明，与Sc2O3与W机械混合制备的混合基含Sc阴极相比，采用液固掺杂法制备的阴极，Sc2O3分布均匀，阴极耐高温和抗离子轰击能力强，发射性能优异。     

AN INVESTIGATION ON SECONDARY EMISSION PROPERTIES OF IMPREGNATED BARIUM SCANDATE DISPENSER CATHODE

A scanning electron probe is used to study the secondary emission properties of the im-pregnated barium scandate dispenser cathode, the influence of the activation on the secondary emis-sion property, the secondary emission image and the secondary emission distribution over the surfaceof the cathode. At optimal activation, δ_m=3.56 (E_(pm)=700eV). The activation has a larger effect onδ when the activation temperature is higher than 1100℃. The distribution over the surface of thecathode is non-uniform. The half-peak width of the distribution curve over the surface is 0.4. Theexperimental phenomena are discussed in relation to surface analysis of the cathode. The theoreticallyderived binomial distribution curves over the surface fit much better with the experimental results.     

NEW METHOD FOR MEASURING SECONDARY ELECTRON EMISSION OF THERMIONIC CATHODE AND ITS APPLICATION

By using correlation-detection technique and improving structure of the test tube,the background noise of thermionic-electrons and space charge effect are restrained.The sec-ondary emission coefficient δ of thermionic cathode at high temperature has been studied.Theδ of impregnated scandate cathodes increases exponentially with increasing temperature at lowenergy and current of the bombardment electrons;at high energy or current of the bombardmentelectrons the temperature has little effect on δ.The research shows that an enhanced thermionicemission occurred when the cathode works at high temperature and under electron bombardment.These phenomena are discussed in terms of “internal field model”.     

Improvement of the performance of the dispenser cathode with Re as a middle layer

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.     

Estimation of dispenser cathode surface temperature of a practicalpotted heater cathode assembly

The heat transfer through the porous and/or infiltrated potted heater-cathode structure is simulated by a numerical model. The model includes heat conduction through a porous potting having isometric pore shape and uniform size (310 μm in alumina potting and 20 μm in tungsten cathode pellet), imperfect interface heat transfer effect and radiative boundaries. In addition to the transient study, a steady-state analysis, using the numerical model has also been done for a commercial Spectra-Mat cathode. The predicted results have been compared with the experimental measurements and are found to be in good agreement     

Ka波段冷阴极磁控管启动特性研究

冷阴极磁控管是一种性价比很高的可靠微波源,它具有瞬时启动、寿命长、可靠性高、系统容易实现小型化的优点。选用钯钡合金和难熔金属钽作为冷阴极材料,钽环作为一次发射体,由场致发射提供一次电子,钯钡合金为二次发射体,钯钡合金在一次电子的轰击下产生二次电子,两者提供磁控管阴阳极电流,实现磁控管正常振荡。从理论上详细分析了钽环厚度和钯钡合金温度对冷阴极启动特性的影响,基于理论分析结果,开展不同钽环厚度和阴极温度条件下磁控管工作性能研究,最终选用厚度为0.05 mm 的钽环作为冷阴极一次发射体,阴极工作温度在315~836 益之间,成功研制输出功率20 kW的Ka 波段冷阴极磁控管,冷启动稳定时间小于5 s,工作寿命超过500 h     

RESEARCH ON THE EVAPORATION PROPERTY OF IMPREGNATED DISPENSER CATHODE BY AES

During the activation and ageing,the evaporation components and rates from 4.56:1.44:2impregnated dispenser cathode have been determined by the vapor-collect method based on the Augerelectron spectroscopy(AES).(1)The evaporation rate of a cathode after ageing differs from that of a justactivated cathode by a factor of 5 to 10.The evaporation energy of the former is 4.58 eV,and that of the latter is4.34 eV.(2)At operating temperature,the metallic barium in the evaporated materials is about 90%,and thebarium oxide is about 9.3%.(3)Blow 1000℃ the evaporation of Ca is not significant;over 1150℃ the Ca startsevaporating rapidly,particularly in the activation process,it may approach 3.5% at 1250℃.     

涂敷法制备的碳纳米管阴极的场发射研究

研究了用涂敷法制备碳纳米管阴极的新工艺和改善其场发射特性的新方法,裂解法获得的碳纳米管与有机粘合剂等混合、研磨,直接涂敷在Si基底上,二极管结构测量的结果表明,碳纳米管阴极有较低的开启电场(1．25～1．5V／μm),场强为5V／μm时,电流密度达到了42μA／cm^2,F—N曲线也非常符合场发射规律。浆料中粘合剂的比例增大时,碳纳米管阴极的场发射性能会有所降低,施加外电场会改善其场发射特性。     

一种自热式阴极的横向放电特性

本文以石墨阴极为例介绍了一种自热式阴极的横向放电特性,指出热电子发射是该阴极的主要机理。     

直径155mm钪酸盐阴极组件研制

热阴极不仅应用在微波电真空器件中,还可应用到高能电子线性加速器中,这种电子加速器通常需要具有上千安培发射电流的电子源.本文主要介绍了某加速器上的直径155mm钪酸盐热阴极组件的研究过程和初步测试结果.模拟分析和实验结果表明,该热阴极组件具有较好的结构稳定性;热子功率可达3200W,在1100℃时能提供2690A的脉冲发射电流,电流密度达到14.3A/cm2;同时单脉冲和三脉冲测试都表现出良好的电流稳定性和一致性.     

O+阴极低发射不良的分析和改善

2003年末和2004年初,华飞彩色显示系统公司使用O 阴极的生产线连续出现较高的低发射不良率,我们对这些批次发射不良问题作了研究和改善.经分析发现低发射阴极粉层表面可以见到大面积的变色,同时还有黑点,进一步分析又发现黑色斑点通常会在镍含量增加的情况下出现.文章分析了废品管发生发射不良的机理,并对分析推断的不良模型进行了模拟实验验证,最后利用分析推断结果,提出了针对性的改善方案,方案在生产中得到了验证,低发射问题得到解决.     

掺氧化钇钡钨阴极的表面特性研究

以掺氧化钇的钡钨阴极作为研究对象,利用现代表面分析技术,包括发射式电子显徽镜、扫描电子显微镜、俄歇电子谱仪和高分辨率x射线光电子谱仪等,进行了综合研究,获得了阴极发射性能、表面形貌和表面化学等实验结果,并对实验结果进行了讨论。     

多孔硅场致电子发射

研究了多孔硅冷阴极的场致电子发射特性，实验表明采用电化学阳极腐蚀、氧化、蒸电极等工艺可以制备一种平面薄膜型多孔硅冷阴极。在超高真空环境下测量了多孔硅冷阴极的电子发射特性。     

亚微米结构新型含钪扩散阴极性能的研究

本文研究具有氧化钪掺杂钨基体钪酸盐阴极的性能.为了改进氧化钪的分布均匀性及提高阴极表面钪的扩散补充能力,分别采用液固掺杂和液液掺杂的方法制备了Sc2O3掺杂W粉基材,研究了利用这种钨粉制作多孔钨基体的工艺技术和多孔体的微观结构.研究表明在改进压制、烧结技术的基础上,可以获得具有适当孔度的亚微米结构多孔基体,氧化钪在基体中的分布得到进一步改善,在这种基体中铝酸盐的浸渍率可以达到常规浸渍阴极的要求.发射试验结果表明,这种阴极在850 ℃的工作温度下空间电荷限制的电流密度超过30 A/cm2,在超过2000 h的寿命实验过程中发射仍持续上升,因而在要求高电流密度和一定寿命的微波电子管中具有光明的应用前景.研究还证实多孔体的结构越趋细微,越有利于阴极的发射均匀性和耐离子轰击的性能改善.     

Current–voltage characteristics of AlCdO Schottky contact on the polished and unpolished p-type Si surfaces with and without light illumination

In this study, the current-voltage characteristics of the AlCdO/unpolished p-type Si and AlCdO/polished p-type Si Schottky diodes with and without light illumination were examined. It is found that the Schottky barrier height (the series resistance) of the AlCdO/unpolished p-type Si Schottky diode is higher (lower) than that of the AlCdO/polished p-type Si Schottky diode. The power conversion efficiency of the AlCdO/p-type Si devices in the light (AM 1.5 G, 100 mW/cm²) was improved by increasing built-in potential at the AlCdO/p-type Si interfaces and reducing the device series resistance and surface reflectivity. It is shown that the device surface roughness plays an essential role in improving the device performance.     

Field-emission lighting tube with CNT film cathode

A novel cylinder-shaped structure field emission lighting tube (FELT) was fabricated. As an emission cathode the carbon nanotubes (CNTs) film were grown directly on the tungsten wire by pyrolysis of iron FePc, and were mounted by using elastic assembling technology. The model of electric field of this FELT was established. The electrons emitting characteristics of electronic field was measured. FELT can reach a static brightness of ∼1.6×10³ cd/m² and can be operated at 180 V. The turn-on field is 0.9 V/μm. When electronic field E=2.0 V/μm, the current density J=320 A/m².     

铁电阴极电子发射实验研究

为提高铁电阴极材料的电子发射电流密度及电子束品质,采用等静压成型工艺制备PZT铁电阴极样品,研究了真空度、温度、极间距、收集极和极间铜网等测试条件对其电子发射性能的影响。结果表明:利用等静压成型工艺制备样品,并进行硅橡胶绝缘层保护,在真空度高于10–3Pa,极间距为2.5mm,并在极间添加铜网,采用石墨收集极情况下进行电子发射实验,可获得铁电阴极样品测试最佳效果。     

印刷电路板预电离TEA CO2激光器的阴极表面预电离研究

弧光放电不利于TEA CO2激光器输出高功率激光,通常采用预电离技术来获得主电极间的均匀辉光放电。印刷电路板预电离较其他紫外光预电离方式具有更好的预电离强度和预电离均匀性的结合,有利于产生高重复频率和高平均功率的脉冲激光。本文研究了印刷电路板预电离TEA CO2激光器中有、无紫外光体积光电离的两种不同预电离结构形式,主放电均匀性实验表明,在无紫外光体积光电离的情况下,也可以获得放电均匀性很好的大体积主放电。这说明在印刷电路板预电离中起主导作用的是阴极表面的预电离效应。本研究结果对探讨TEA CO2激光器的预电离放电机理具有参考价值。