常开型后栅极场致发射显示板工作特性的研究

常开型后栅极场致发射显示板是一种新型的场致发射器件.它直接利用阳极使阴极产生场致电子发射,而通过埋在阴极之下的栅极上施加负电压来阻止阴极产生场致电子发射来调制显示所需的图像.为了研究该场致发射显示板的阴极发射特性,本文采用有限元法对场致发射区域内的电场分布进行了模拟计算,用Fowler-Nordheim(F-N)公式计算了阴极表面的发射情况.并研究了阳极电压、阴极电压、阴调距、阴极宽度和阴极厚度等参数的改变对阴极发射特性和栅极调制能力的影响.计算结果显示阴极发射特性和栅极调制能力与上述电参数和结构参数关系密切,从而为优化设计这种显示器件提供了方向.     

行波管阴极组件动态热耗散分析及优化设计

阴极作为行波管的“心脏”，其内部结构的热耗散是影响行波管预热时问的关键问题，热传导和热辐射是引起阴极组件内部热耗散的最重要因素。建立了阴极组件热状态有限元分析方程，利用有限元ANSYS软件对阴极组件动态热耗散进行模拟分析。提取热流矢量图及温度分布图，并获得阴极达到稳态的预热时间。对实际样品进行实验验证，证明了有限元模拟方法是可行的。基于瞬态热模拟分析结果，优化设计了阴极组件中关键部件的结构及材料，有效地缩短了阴极预热时间，提高了行波管快速反应能力。     

变掺杂GaAs光电阴极的研究进展

从变掺杂阴极的结构种类、变掺杂GaAs光电阴极的光电发射机理、制备技术以及变掺杂结构对阴极性能的影响等方面介绍了当前国内研究变掺杂GaAs光电阴极的进展.目前该工作还处于起步阶段,理论研究还有待于进一步深入.开展变掺杂阴极研究是我国走自主创新道路、提高国内三代微光器件性能的有效途径.     

微波管环境下场发射阵列阴极的工作稳定性研究

场致发射阵列阴极在微波管中的应用无疑是微波真空电子器件的一场革命,但经过多年的研究和发展目前仍没有解决微波管环境下阵列阴极的工作稳定性和寿命问题.虽然国外也有一些利用这种冷阴极的行波管和预群聚速调四极管的实验,但都存在同样的寿命问题.本文对场致发射阵列阴极在微波管环境中的工作稳定性和失效机理进行了分析研究,主要原因是真空度、微波管的残余气氛、电子枪区域的高压打火和离子的回轰影响了阵列阴极的稳定性和寿命等,提出了场致发射阵列阴极在结构、发射体材料、处理工艺、整管排气封接过程等方面的改进方法,以使这种阴极能适应微波电真空器件的特殊环境.     

钡钨阴极用大电流低蒸发发射物质的研究

采用不同工艺制备了浸渍钡钨阴极用的铝酸盐(612),并对其发射性能进行了测试,结果表明,采用二氧化碳烧结的发射物质发射性能最好.利用飞行时间质谱(ToFMS)测试了真空本底、浸渍阴极蒸发物的成分.研究了阴极蒸发速率与阴极温度的关系.比较了不同工艺制备的铝酸盐(612)蒸发速率的大小.     

星载行波管高效率、高可靠阴极热子组件研究

阴极热子组件是星载行波管的核心部件,其性能的好坏直接影响到整管的性能和寿命。由于星载行波管工作环境特殊,要求在保证阴极正常工作的前提下,尽可能地降低阴极热子组件的加热功率以提高阴极热子组件可靠性、延长阴极热子组件寿命,同时阴极热子组件必须具有良好的抗振性能。本文利用ANSYS有限元软件对某星载脉冲行波管栅控电子枪阴极热子组件进行了热学和结构动力学性能分析和研究,通过优化阴极热子组件支撑结构和尺寸,降低了它的加热功率,并进行了热学实验验证;同时为了保证其力学可靠性,分析了阴极热子组件在随机振动条件下的力学性能。研究结果表明,新阴极热子组件结构加热功率由10.50 W降低至8.21 W,轴向尺寸缩短了45.4%,满足某星载行波管小型化的需求,结构同时符合抗机械振动性能的要求。     

光电阴极的研究进展

光电阴极的材料决定了光电发射的量子效率、暗发射电流和出射电子能量分布等重要性能。本文介绍各种类型的光电阴极发射材料,包括碱金属和半导体材料。其中重点介绍半导体材料中的多碱光电阴极和负电子亲和势(NEA)光电阴极,并对多碱光电阴极的制备流程及性能测试和影响NEA光电阴极量子效率等因素进行详细的分析。     

自维持电弧放电模式下碳纳米管的制备及机理

通过实现不同条件下的电弧放电,用扫描电子显微镜(SEM)和透射电子显微镜(TEM)对阴极沉积物中碳管的形貌和微结构进行表征,得到碳管的形貌和微结构与放电条件之间的一些对应关系.提出整体温度较低的沉积物边缘具有较高的局部温度、较大的碳离子流,并提出阴极上存在边缘的场致冷阴极发射和边缘以内的热阴极发射,它们分别起到引起边缘硬壳的形成、为碳纳米管的生长提供必要条件的作用.通过深入理解电弧放电过程,从而制备高质量具有特定结构的碳纳米管.     

后栅极场发射显示板结构参数在公差范围内变化对工作特性的影响

后栅极场发射显示板是一种常用的场致发射器件。该器件结构由阳极、阴极和栅极组成,并且栅极置于阴极背面。本文采用模拟计算的方法研究了标准结构场发射区域内的电场分布、阴极表面的发射情况、电子轨迹和着屏束斑。并研究了关键结构参数在公差范围内变化对阴极发射特性和阳极着屏束斑的影响。计算结果显示结构参数在公差范围内的变化对阴极发射状况,阳极束斑栅极调制特性的影响很小,进而证明了后栅极结构对工艺一致性要求较低。     

真空度对阴极材料微结构影响的电子显微分析

针对阴极失效影响因素中的真空度问题,利用扫描电子显微镜以及能谱仪作为研究手段,分析对比了未老炼以及在不同真空条件下老炼的阴极的微观结构以及成分差异,结果表明,真空度降低,阴极中发射物质将与空气中的水汽以及氧反应,导致微观结构发生变化,这对于行波管的封装可靠性提出了较高要求.     

Cathode spots on the surface of nanostructured W alloys

The tracks of cathode spots produced after arcing on the surfaces of nanostructured W alloys were investigated using a scanning electron microscope (SEM). For nanostructured W–2%ThO₂ cathodes, the distribution of cathode spots was dispersed and their geometrical properties were completely controlled by the shape and size of ThO₂. For nanostructured W–20%Cu cathodes, the spots were also separated on Cu-rich phase. The results showed that cathode spots on the surface of nanostructured W alloys were quite different from those on the surface of commercial W alloys with coarse grain size, and the microstructure of the cathode materials had significant influence on the cathode spots propagation. Also, space-charge regions induced by internal electric field at the interface which responded to the effect of microstructure on cathode spots were suggested.     

Low perveance confined-flow Pierce gun for a 0.14 THz broadband folded waveguide traveling wave tube

An approach for designing an electron gun for a high efficiency, high linearity 0.14 THz traveling wave tube (TWT), has been presented. A Pierce electron gun of beam perveance 0.0047 μP has been designed for a high gain, high linearity and high efficiency 0.14 THz TWT using CST STUDIO SUITE Charged Particle Simulation soft and electronic optical software TAU. The initial gun geometry, as obtained from the Vaughan iterative synthesis method, has been used as input for simulation of the electron gun. An M-type dispenser cathode of diameter 0.8 mm has been used for cathode loading of 2.75 A/cm². The magnetic focusing with integral-pole-piece barrel assembly and periodic-permanent magnets (PPM) have been designed using CST and TAU. The practical problem of linking requisite cathode flux to the cathode for confined flow of the electron beam with low convergence factor has been sorted out by gradually increasing the PPM magnetic field. The magnetic field has been increased in steps from the gun and over the first five magnets varying from Brillouin field (B_B) value to twice B_B for achieving the electron beam with scalloping less than 10%. Simulation results show that the design method is reasonable for obtaining a 0.14 THz TWT electron gun and periodic-permanent magnets (PPM).     

Low perveance confined-flow Pierce gun for a 0.14 THz broadband folded waveguide traveling wave tube

An approach for designing an electron gun for a high efficiency, high linearity 0.14 THz traveling wave tube (TWT), has been presented. A Pierce electron gun of beam perveance 0.0047 μP has been designed for a high gain, high linearity and high efficiency 0.14 THz TWT using CST STUDIO SUITE Charged Particle Simulation soft and electronic optical software TAU. The initial gun geometry, as obtained from the Vaughan iterative synthesis method, has been used as input for simulation of the electron gun. An M-type dispenser cathode of diameter 0.8 mm has been used for cathode loading of 2.75 A/cm². The magnetic focusing with integral-pole-piece barrel assembly and periodic-permanent magnets (PPM) have been designed using CST and TAU. The practical problem of linking requisite cathode flux to the cathode for confined flow of the electron beam with low convergence factor has been sorted out by gradually increasing the PPM magnetic field. The magnetic field has been increased in steps from the gun and over the first five magnets varying from Brillouin field (B_B) value to twice B_B for achieving the electron beam with scalloping less than 10%. Simulation results show that the design method is reasonable for obtaining a 0.14 THz TWT electron gun and periodic-permanent magnets (PPM).     

Change in cathode spot behavior in vacuum arc cleaning with application of polyethylene glycol

The authors investigated the effect of polyethylene glycol (PEG) application on the oxide removal action of cathode spots. Experimental observations revealed that the cathode spots formed on the oxide layer on the metal surface can be classified into two different sub-types, slow cathode spot (SCS) and fast cathode spot (FCS). Two different sub-types of cathode spots could exist in a same test piece at a same time. The removal rate of oxide depends on the mixture ratio between FCS and SCS. The more the cathode spots belonged to FCS, the faster the oxide layer is removed. The application of PEG enhances the probability of the presence of FCS.     

阴极弧斑放电的机理分析

介绍了阴极弧斑放电的基本特征。参考前人的研究模型和最新的实验结果,系统地分析了阴极弧斑放电的机理和过程：电子的爆裂发射模型;热场致发射理论;阴极电位降区满足的Ｍａｃｋｅｏｗｎ 公式;阴极弧斑在磁场中的运动机理。最后讨论了气压对弧斑运动的影响,解释了阳极弧斑放电特征。     

Study of the direct current breakage process in an external nonuniform magnetic field

We study experimentally the influence of an external nonuniform magnetic field with transverse and longitudinal components on the electric characteristics, plasma configuration, and cathode spot arrangement of vaccum-arc discharge. It is revealed that for a cylindrical cathode, cathode spots are nonuniformly distributed on the cathode surface, the spot configuration has no axial symmetry, and the arrangement of spots changes in time depending on the induction value of the external pulsed magnetic field. With an increase in induction, spots (on average) are arranged closer to the cathode, i.e., displaced to the region of weaker transverse field. For two cathode geometries, the probabilities of direct current breakage depending on the induction of the external nonuniform magnetic field are experimentally determined. To determine the conditions of current breakage, a three-dimensional mathematical model of ion motion is suggested and the current breakage criterion is formulated. The trajectories of fast cathode ions in an electrode system with a ring cathode have been calculated using the model. Calculations were performed in a nonuniform magnetic field, the radial and axial components of which have been measured experimentally. It is shown that conditions of current breakage determined with this criterion agree with the results of experiment.     

Influence of the tip effect of a carbon nanostructure on low current electrical arc initiation

During their setting off, circuit breakers and vacuum switch devices are accompanied by an electric arc whose physical and chemical properties are governed by emissive current sites at the cathode surface called cathode spots. Assuming the continuity of the current on the cathode surfaces, the cathode spots contribute to supply the electrical arc by electron emission and material ejection. Thus they cause erosion on the contact electrodes inducing a dysfunction of contactors. The apparition of these cathode spots is due essentially to dust particles and surface irregularities at different scales. This experimental work represents a contribution to the understanding of the electrical arc behaviour by an investigation at submicronic scale on the influences of nanostructured carbon tips on the electric arc initiation and the cathode spots birth.     

Vacuum Arc Discharge on Integrally Cold Cathode

Initial researches of the existence of a cathode spot on the working surface were conducted in vacuum arc plasma sources of the coaxial design. The moving of the cathode spots on the limited sizes working surface does not give full picture of the development of the arc discharge. This article describes the vacuum arc plasma source of extended design generating the directed belt plasma stream and operating in pulse mode. The researches carried out give additional information about development of the cathode spots of the vacuum arc discharge. It is found that the speed of the cathode spots' motion depends on the cathode temperature.     

Dynamics studies of cathode spots in a vacuum-arc discharge with ring electrodes

The effect of an external pulse magnetic field with axial and radial components on electric characteristics of the discharge and the configuration of cathode spots of a vacuum arc discharge with ring electrodes is studied experimentally. For arc currents within the range of 0.05–2 kA, shots of the cathode spots at different instants of time are obtained. The dependences of the number of the spots on the discharge current and the mean current per spot are determined. It was found that the expansion rate of the cathode spots area depends significantly on the instant value of the discharge current. It is shown that, when the pulse magnetic field is applied, the discharge voltage increases and the discharge current and number of the cathode spots decreases. It was found that the current interruption is a probability process. The probabilities of the current interruption depending on the maximal value of the external pulse magnetic field induction are determined.