In this paper we mainly describe the research progress of oxide cathode and its application in vacuum electron device, which includes a Ni-Sc sponge oxide cathode, a reservior oxide cathode, and a NiMoFe alloy direct-heated oxide cathode.

Based on the development of a magnetron injection electron gun（MIG） for gyrotron oscillator operating at 140 GHz and with about a megawatt output power, the temperature homogeneity of the cathode and thermal deformation of the MIG were analyzed with ANSYS code. Under an improved temperature homogeneity of the cathode, the geometrical and electrical parameters have been adjusted and optimized to eliminate the effect of thermal deformation on beam trajectory. The simulated temperature of the cathode will be compared with the tested one for evaluating the rationality of the simulation model, which may be helpful for the actual design.

多孔金属材料是一类具有优异性能的新型材料.本文首先简述了多孔金属材料的几种常用制备方法及应用领域.然后对多孔钨材料在微波真空器件、核聚变及空间电推进技术等领域的应用进行了介绍,指出了多孔钨材料及零件制备中存在的问题,针对这些问题对多孔钨材料及零件制备工艺进行了深入研究.利用射流分级技术对钨粉进行了分级,激光粒径测试仪的分析结果表明,分级后的钨粉颗粒度分布更加集中.采用气体纯化装置对烧结用氢气中残余的水和氧进行了净化,使氢气的露点从纯化前的-50℃降到纯化后的-90℃以下,为制备出无氧化的多孔钨材料及零件提供了很好的烧结环境.利用冷等静压技术和高温烧结技术制备出多孔钨材料,压汞仪分析表明钨粉分级使多孔钨材料的比表面积增大,闭孔率大大降低,孔度更加均匀一致.采用真空浸铜的方法制备出多孔钨铜合金材料,与传统氢气浸铜方法相比,真空浸铜的浸渍率提高了4％以上.采用真空去铜法净化了多孔钨铜零件,结果表明该方法具有处理时间短、去铜彻底、对环境无污染等优点.

本文总结了用于真空微波电子器件的浸渍阴极的蒸发规律,通过分析提出了浸渍阴极预处理工艺,建立了超高真空装置.在超高真空环境下,将浸渍阴极灯丝加热,使阴极温度升高到1100～1200℃,保持1～200h(温度和时间依不同微波管型而定).预处理工艺解决了浸渍阴极发射与蒸发的矛盾,现已建立数十台、几十个工位的浸渍阴极预处理设备,大大提高了微波真空电子器件中电子枪的绝缘性能,减小了栅发射.浸渍阴极预处理工艺还可以加速检验热子的可靠性,从而避免微波器件在使用过程中才发现热子短路、热子缺陷及热子焊接点不牢等因素造成热子断路的问题,提高了微波真空电子器件中热子的可靠性.

微波真空电子器件广泛应用于雷达、卫星通信、电子加速器等方面,热子组件是微波真空电子器件中最为核心的部件之一,其性能将直接影响微波源的可靠性和寿命.为了克服传统热子组件制备工艺的缺点,避免热子组件可靠性差和寿命短的缺陷,提出了一种热阴极用熔融热子组件的制备方法,采用高温真空烧结技术将热子与绝缘材料烧结熔化在一起,提高了热子组件的致密性,降低了残余气体的吸附量,增强了热子组件的抗冲击性能,克服了热丝变脆的缺点.

In this paper we mainly describe the research progress in the lifetime testing for several kinds of high-temperature W base directly-heated oxide cathodes. The test results show that the lifetime of the 5% wt Sc 2 O 3 doped Y-Gd-Hf-O coating cathode is reached 6100h with a dc load of 1.0A/cm2 at 1500 °Cbr. The lifetime of the La2Hf207 coating cathode is beyond 11600h with a dc load of 0.65A/cm2 under 1400-1450°Cbr operating temperature. The lifetime of the Y2Zr207 coating cathode is also beyond 11600h with a dc load of 0.50 A/cm 2 under same temperature.

The impact of the electron bombardmenton degassing behavior of vacuum electronics materials was investigated and exemplified withoxygen-free copper.The outgassing rate was precisely measured in orifice conductance method with the lab-built test-platform at a base pressure of 5.0×10-7 Pa.The results show that the degassing rate of O-free Cu was linearly proportional to the voltage,width and frequency of the pulsed electron beam.The chemi-sorbed single atoms dominated the bombarded Cu-surface after exposure to air for 150h,possibly because of the surface charge accumulation;and the previous lowest outgassing-rate was rapidly reached after removal of the chemisorbed species by electron bombardment.The desorbed gases were identified as H2,H2O,N2 and CO2.We suggest that the reliability and service lifetime of microwave vacuum devices may be significantly improved by degassing the anodes and/or collectors with the electron beam emitted from hot-cathode and/or electron guns.

The development of modern satellite communication technologies is imposing higher demands on the lifetime and reliability of the microwave vacuum electronic devices, which directly depend on the evaporation properties of the extensively used Monel and stainless steel. Therefore, it is of vital importance to study the evaporation properties of these two types of metallic materials. For the first time, as far as we know, this paper proposes to study the evaporation properties of metallic materials using time-of-flight mass spectrometer (TOFMS). The components and the contents of the vacuum background, the evaporants from the Monel and from the stainless steel have been measured using the TOFMS, respectively. After the pressure of the measurement chamber is below 4.010-8 Pa, the TOFMS is used for the metallic materials working at different temperatures. They are respectively acquired when the Monel and stainless steel are at room temperature on operate between 750 to 900 ℃ under a pressure of 1.010-6 Pa. The measurements are carried out rapidly and in high sensitivity. As disclosed by the measurements, Mn and Cu began to evaporate when the Monel and the stainless steel are heated to 800 ℃, which is still far below the melting points of the two alloys (1243 ℃ and 1080 ℃). When the Monel and the stainless steel are further heated to 900 ℃, the evaporation of Mn, Cu, and Cr becomes quite considerable. Once the evaporated Mn, Cu, or Cr deposit on the ceramics for the insulation in an electron gun, its insulation will be deteriorated. Hence, the Monel and the stainless steel are not suitable to be use as the components in cathode electron guns, especially those used in the devices that are to work a long lifetime in high vacuum. Moreover, the Monel and the stainless steel are not suitable for used as the components that are often under the electron bombardment, e.g., anodes and collectors, either. The SEM images and XRD of the heat treated surface structures of the Monel and the stainless steel in ultrahigh vacuum (1.010-6 Pa) have also been studied. On heating at 900 ℃ for 30 and 120 min the surface structure and composition change remarkably and a significant reduction in Mn and Cr is visible, and also a large number of holes and crystal boundaries emerge on the surfaces of the two metallic alloys. With increasing heating time, the boundaries will grow larger and larger. As a result, the strength of the two metallic materials becomes weaker and gas permeation and leakage even occur. Therefore, it can be concluded that the components made from Monel and stainless steel, especially those with thin walls, should not be heated to high temperatures in ultrahigh vacuum for a long time. The above phenomena are analyzed in detail theoretically and the proper and feasible application methods of the metallic materials are explored in device design and technological process control. These works are expected to contribute to the prolonging of the lifetimes of the satellites, and will lead to tremendous economic benefits.

As the core component of space traveling wave tubes, the cathode-heater assembly is required to be stable, reliable, long life and low power consumption. In this paper, an estimation method of thermal contact resistance is proposed, and the thermal characteristics of cathode-heater assembly structure are simulated. Meanwhile, thermal experiment is designed and undertaken, and the whole temperature distribution of cathode-heater assembly structure under a variety of heating power is obtained for the first time. Furthermore, the thermal boundary and excitation of cathode-heater assembly structure is modified, and the values of thermal contact resistances are obtained by interactive method. Finally, a high reliable thermal model of cathode-heater assembly structure is obtained. It is revealed that cathode temperature calculating accuracy is within 5%, and the calculating error of whole structure is less than 72°C .

Microwave vacuum devices are used in a wide variety of areas,such as radar,space technology,electron accelera-tors,free electron lasers.The cathodes,i.e.the electron sources,are the cores of high-power microwave sources.Their per-formances directly determine the output power,lifetime and other properties of the microwave sources.It is necessary to know the actual temperature of a thermionic cathode.The temperatures of an impregnated cathode,a coated cathode and a cathode side (molybdenum tube)have been tested by infrared thermometer,optical pyrometer and thermocouple thermometer (platinum and rhodium-platinum).The results show that the temperature of an impregnated cathode tested by infrared thermometer and optical pyrometer is similar to that by thermocouple thermometer,so the temperatures of impregnated cathode tested by infrared ther-mometer and optical pyrometer are very close to the actual temperature by thermocouple thermometer.The temperatures of coa-ted cathode tested by infrared thermometer and optical pyrometer are lower than the actual temperature of the cathode tested by thermocouple thermometer about 50 ℃.The temperatures of the cathode side (molybdenum tube)tested by infrared thermometer and optical pyrometer are lower than the actual temperature of the cathode by thermocouple thermometer about 60 ℃.Since the physical and chemical changes arise on the cathode surface,the temperatures of the cathode surface tested by infrared thermome-ter and optical pyrometer increase about 30 ℃ heated at about 1150 ℃ within 100 min.These results will be affected by the mo-lybdenum processing technology on the surface of the material,coating material,thickness of the film,the film density and other factors.Infrared thermometer and optical pyrometer are strongly dependent on the thermal radiation coefficient of the test sur-face,and it is very difficult to accurately obtain the thermal radiation coefficient of some materials.

The interference fit of the three components of the slow wave structure of the space-borne helix trav-eling wave tube,including the clamping rods,tube housing and periodic permanent magnet unit,was mathematically modeled,theoretically analyzed,and numerically simulated in finite element method with software Inventor and AN-SYS.The impact of the mould displacement (extrusion)on the stress,strain,tube’s deformation,and buckling de-formation originated from random fabrication error,was investigated.The calculated and simulated results provide the security scope and success probability of the interference fit.In addition,dependence of the interference fit on the length and thickness of the tube housing was also simulated.The interference fit was found to strongly depend on the thickness,but weakly on the length of the tube;the thinner the tube,the weaker the yield strength,and the higher success probability.

Microwave vacuum devices are used in a wide variety of areas, such as radar, space technology, electron accelerators and high-power microwave weapons at the future military frontiers. The cathodes, i.e., the electron sources, are the cores of the high-power microwave sources. Nanoparticles have many physical and chemical properties that their corresponding bulk materials do not have, such as surface effect and small-size effect, etc. Based on our previous work on the M-type cathode, we have proposed a strategy to develop a new type cathode. We deposited a layer of thin film of metal nanoparticles on the traditional Ba-W dispenser cathode. Thus the N-type cathode demonstrated some features different from the traditional M-type cathode. The study of the electron emission properties of this N-type cathode would promote the understanding on the electron emission and expand the applications of the nanomaterials. Nanoparticle thin films were grown by magnetron sputtering at room temperature. The results showed that the particle size of the films depended on the deposition rate in the nucleation stage of the films. The effect of thin film characteristics on thermionic emission of dispenser cathodes has been investigated. The chemical components of the vacuum background, the evaporants from an N-type cathode and an M-type cathode were respectively analyzed using a time of flight mass spectrometer (ToFMS). The results have proved that the ToFMS is one of the best tools for studying the evaporation phenomena of impregnated cathodes. Finally, the electron emission performance of the N-type cathodes was studied. I-V characteristics showed that the DC emission current density was 30 A/cm2 and its lifetime was 600 h. The pulse emission current density was 108 A/cm2 and its lifetime was 1500 h.

介绍一种用于移动术中放疗电子直线加速器中栅控电子枪阴极的设计、研制、发射性能测试及其在该加速器中的应用情况.基于栅控电子枪低蒸发、高可靠、长寿命的设计要求,研制出了钨基底平均孔度为21.6％、浸渍311主要单一相铝酸盐、覆Os-W膜浸渍覆膜钡钨阴极.测试结果表明:该阴极在工作温度950℃,直流发射电流密度5.8 A/cm2,在1000℃,脉冲宽度10μs,脉冲发射电流密度24.1A/cm2,工作温度950℃,直流支取3.0 A/cm2,14000h寿命发射稳定.该阴极制备栅控电子枪在医疗加速器中获得成功应用.

微波真空电子器件广泛应用于雷达、卫星通信、电子加速器等方面,热子又是微波真空电子器件中最为核心的部件之一,其性能好坏将直接影响微波源的可靠性和寿命.为了克服传统热子制备工艺的缺点,避免螺旋腿部分的钨或钨合金丝出现损伤,提供一种高可靠热子制备方法,采用高温焊料焊接技术将螺旋丝与插腿焊接在一起,从而制备出具有螺旋腿与插腿之间接触电阻小、耐震动性能好、抗热冲击性能好和可靠性高等优点的热阴极用热子.采用新方法制备的热子在ll00℃高温下寿命已超过3000h,没有出现断路现象,目前在各种微波管上使用了新方法制备的热子,没有出现一只断路.

Superfine Al2O3 particleswere deposited on the Momould by flame plating,then the denseα-Al2O3 coatingon the surface of MoMould were fabricated by firing at high-temperature in H2 atmosphere.The accuracy of mould was high,and the coating Al2O3 layers were infiltrated by solder.The disadvantage of stainless steel,graphite and pure Mo as mould wereovercome.

该文主要研制一种用于HIRFL-CSR电子冷却装置的氧化物阴极,测试了该阴极在普通试验二极管中的发射性能及寿命,研究了成型阴极表面温度均匀性及其分解激活过程.结果表明,阴极支取直流发射电流密度0.5 A/cm2,工作温度750℃～800℃时具有很好的发射均匀性,电流加速寿命结果表明,该阴极在800℃,寿命超过18000 h.

In this paper, an electron gun for a linac E-beam irradiator is developed with a replaceable cathode and filament. The structure of cathode and filament and the concentric technique, with molds and clamps, are described in detail. The electron gun was assembled with care to reduce the error, and ensure the concentricity of electron gun. The test results indicated a 99.99% pass ratio of the electron beams at 60–65 kV. The electron gun design meets the technical requirement of clients.

In order to meet the need of a sheet beam electron gun testing, we have developed a new sheet beam M-type cathode in elliptic cylinder shape with major axis 10 mm, stub axle 4 mm and radius 17 mm. In this paper, the main manufacturing procedures of the cathode are discussed. The test results of the sheet beam electron gun indicate, the beam transmission rate is up to 98.6%, the current density of the cathode reaches 8.9A/cm2. These results provide a good foundation for developing higher performance sheet cathodes in the future.

The oxide cathode is still wildly used in vacuum electronic devices as electron sources. With the ongoing development of electronic devices, the requirements for the emission characteristics of the cathode have to be enhanced to suit the new applications. It is a promising research direction improving the emission characteristics of the cathode at a low operating temperature and simple manufacture technology. This paper studied the manufacture technology and properties of the oxide cathode and its emission mechanism. Then a new type of oxide cathode is developed and tested for its emission properties and lifetime. Its emission characteristic is better than that of the conventional oxide cathode. Part of properties of the cathode used in HIRFL-CSR Electron cooler is tested. The results show that the new oxide cathode is suitable to the electron cooler applications.