Theoretical research on electron beam modulation in a field-emission cold cathode electron gun

In order to develop miniaturized and integrated electron vacuum devices, the electron beam modulation in a field- emission （FE） electron gun based on carbon nanotubes is researched. By feeding a high-frequency field between the cathode and the anode, the steady FE electron beam can be modulated in the electron gun. The optimal structure of the electron gun is discovered using 3D electromagnetism simulation software, and the FE electron gun is simulated by PIC simulation software. The results show that a broadband （74-114 GHz） modulation can be achieved by the electron gun with a rhombus channel, and the modulation amplitude of the beam current increases with the increases in the input power and the electrostatic field.

Fabrication Research and Property of Enhanced Petaling Cold Cathode with Carbon Nanotube

With high effective screen-printing technique, a new triode field emission display (FED)with enhanced petaling cold cathode was fabricated. For enhancing the field emission performance,a series of improved measures was adopted in the fabrication course. Seen from the fabrication structure of enhanced petaling cold cathode,the bar conducting electrode and the petaling bottom electrode were fabricated with the sintered silver slurry on cathode glass faceplate. The luminescence image with green phosphor was displayed for the sealed enhanced petaling cold cathode FED. The measured results showed that the enhanced petaling cold cathode had good field emission performance. The enhanced petaling cold cathode FED possessed low turn-on electric-field of 1. 95 V /μm,large emission current of 1 389. 6 μA,and high luminance brightness of 1 520 cd /m2 .

A Modified Cold Molybdenum Cathode Penning Ion Source

In this paper, design and construction of a modified cold molybdenum cathode Penning ion source was described. It consists of copper cylindrical anode with two cone ends and two movable cold molybdenum cathodes. The two cathodes were placed symmetrically at two ends of the anode. The modifications were decrease the length of the cylindrical anode to 4 cm instead of 6 cm, transform the copper emission electrode shape from plate of 40 mm length, 25 mm width and 2 mm thickness to disc of 20 mm diameter and 2 mm thickness and transform the inner uncovered area of the emission electrode from slit of 30 mm length and 10 mm width to disc of 5 mm diameter. The copper emission electrode was placed in the middle of the cylindrical anode and has aperture in the center of different diameters. Faraday cup was placed at different distances from the emission electrode aperture. The electrical discharge and the output ion beam characteristics of the modified ion source were measured at different pressures using argon gas. It was found that the optimum operating conditions of the modified ion source are; anode-cathode distance equal to 6 mm, emission electrode aperture diameter equal to 2.5 mm and emission electrode aperture, Faraday cup distance equals 3 cm. The effect of axial samarium cobalt permanent magnet of intensity equal to 300 Gauss on the discharge characteristics of the ion source was determined.

Thin film micro-scaled cold cathode structures of undoped and Si-doped AlN grown on SiC substrate with low turn-on voltage

The field emission characteristics of the AlN thin films with micro-scaled cold cathode structures are tested in the high vacuum system. The aluminum nitride （A1N） thin films with a thickness of about 100 nm are prepared on the n-type 6H-SiC （0001） substrate at 1100℃ by metal organic chemical vapor deposition （MOCVD） under low pressure. The I-V curves and surface micro-images of undoped and Si-doped AlN films are investigated. From the I-V and Fowler-Nordheim plots, it can be seen that the Si-doped AlN shows better field emission characteristics compared with the undoped AlN sample. The obtained turn-on field is 6.7 V/μm and the maximum emission current density is 154 mA/cm2 at 69.3 V for the Si- doped AlN film cathode after proper surface treatment. It is proposed that the relatively low electric resistivity of Si-doped AlN films is significant for electron migration to the surface region, and their rougher surface morphology is beneficial to a higher local electric field enhancement for the field emission.

Plasma characterization on carbon fiber cathode by spectroscopic diagnostics

This paper mainly investigates plasma characterization on carbon fiber cathodes with and without cesium iodide （CsI） coating powered by a - 300 ns, - 200 kV accelerating pulse. It was found that the CsI layers can not only improve the diode voltage, but also maintain a stable perveance. This indicates a slowly changed diode gap or a low cathode plasma expansion velocity. By spectroscopic diagnostics, in the vicinity of the cathode surface the average plasma density and temperature were found to be -3×10^14 cm^-3 and - 5 eV, respectively, for an electron current density of - 40 A/cm^2. Furthermore, there exists a multicomponent plasma expansion toward the anode. The plasma expansion velocity, corresponding to the carbon and hydrogen ions, is estimated to be - 1.5 cm/μs. Most notably, Cs spectroscopic line was obtained only at the distance - 0.5 mm from the cathode surface. Carbon and hydrogen ions are obtained up to the distance of 2.5 mm from the cathode surface. Cs ions almost remain at the vicinity of the cathode surface. These results show that the addition of CsI enables a slow cathode plasma expansion toward the anode, providing a positive prospect for developing long-pulse electron beam sources.

Time-and-space resolved measurements of the emission uniformity of carbon fibre cathode in high-current pulsed discharge

The remaining challenges, confronting high-power microwave （HPM） sources and pulsed power generators, stim- ulate the developments of robust relativistic electron beam sources. This paper presents a carbon fibre cathode which is tested in a single pulsed power generator. The distribution and the development of cathode plasma are observed by time-and-space resolved diagnostics, and the uniformity of electron beam density is checked by taking x-ray images. A quasistationary behaviour of cathode plasma expansion is observed. It is found that the uniformity of the extracted electron beam is satisfactory in spite of individual plasma jets on the cathode surface. These results show that carbon fibre cathodes can provide a positive prospect for developing a high-quality electron beam.

冷阴极真空开关导通特性研究综述

对于空间环境应用的真空开关,可以省去人工环境下的开关密封结构和附属抽真空等设备,有效减轻体积重量,且具有真空环境天成、无需密封、绝缘强度高、恢复速度快等优点,在空间环境中有巨大的应用潜力。首先对国内外的真空开关导通特性研究进展进行了系统介绍,分析了多种类型真空开关的工作特性,评述其优缺点,并对自击穿型沿面闪络真空开关和触发型真空开关的导通机制进行了总结分析;其次分析了关于冷阴极材料的应用研究;然后概括介绍了本课题组在冷阴极真空开关方面的工作进展;最后探讨了冷阴极真空开关的发展趋势,为脉冲功率驱动源的空间环境应用奠定技术基础。

冷阴极触发管工作稳定性研究

随着直列式爆炸箔起爆/点火技术的发展,对其安全性和可靠性提出更高要求,高压开关是该技术中的关键元器件,使用环境也十分苛刻,要求高压开关的电阻和电感小、导通能力高、寿命长、稳定可靠。现普遍使用的一种高压开关—冷阴极触发管自击穿电压和延迟时间的稳定性直接影响了直列式点火技术使用的安全性和可靠性,通过分析放电机理、改善电极表面状态、优化老炼方案并通过试验对比分析,对其工作稳定性进行研究,得出结论:采用电化学抛光提高电极表面状态,小电流和大电流老炼方案稳定放电特性的措施提高了冷阴极触发管自击穿电压和延迟时间的稳定性,提高了冷阴极触发管在直列式爆炸箔起爆/点火技术使用的安全性和可靠性。

小型化冷阴极触发管的研究

冷阴极触发管是电子引信系统中的关键器件,具有开关电流大、使用电压范围宽、温度范围宽、可靠性高、抗干扰性强等特点。针对电子引信系统小型化、集成化、低成本、高可靠发展的需要,本文开展小型化冷阴极触发管的研究,设计并制得样管。通过仿真,给出静电场分布情况。对样管进行电参数和可靠性能测试,结果表明,其工作电压范围为1.2~1.8 kV,且可通过对工作寿命、振动、高低温工作和贮存、冲击等可靠性试验考核,主要参数基本满足现代电子引信的使用需求。

一种冷阴极电子枪的模拟研究

文章通过Computer Simulation Technology粒子工作室软件建立了一种电子通过率极高的微焦点冷阴极电子枪。重点研究了电子枪自身结构对焦点、电子通过率和阴极发射电流的影响。特别是仿照了皮尔斯电子枪的结构,采用了一种弧面阴极,并在此基础上增加了一个阴极凹槽,使电子通过率从75.21%提高到90.26%,同时将近500μm的焦点缩小到50μm以内。最终设计出的冷阴极电子枪在阳极电压为90 kV且栅极电压为1 kV的条件下,电子通过率可达95.41%,在阳极靶面得到的束斑有效焦点尺寸约为45μm。

核电冷源设备的阴极保护及腐蚀智能监测

核电冷源设备具有材质多样化、腐蚀环境苛刻等特点,其阴极保护系统的有效运行和预防性腐蚀管理至关重要,但受空间限制,在设备运行期间阴极保护系统参数无法有效采集,阴极保护系统运行管理存在盲区。基于此,从核电冷源设备的特殊工况和实际需求出发,提出了具有数据采集、存储、远程传输、远程控制、故障预警等功能的阴极保护及腐蚀智能监测方案,通过实际案例分析,验证了此方案可以实现核电冷源设备运行期间腐蚀与防护状态的整体评价和故障预警。

分布式X射线源的发展历史和最新进展

介绍了分布式X射线源的技术概念和历史渊源,分布式X射线源是指可以在一个射线管内的不同位置分别独立可控地产生X射线发射的装置,其理念在X射线CT技术的早期阶段即被提出,目的是解决滑环运动带来的成像速度慢的问题,但是由于技术难度大,早期未能落地实施。随着碳纳米管(CNT)的发现和在冷阴极X射线管中的应用,美国北卡大学在2005年实现了5焦点分布式X射线源的设计和成像研究,引起学界的广泛关注,带动了分布式X射线源的新研究热潮,且热阴极、冷阴极、线阵列、面阵列等众多分布式X射线源的创新研究成果纷纷涌现,进一步介绍了国内外典型研究单位的技术路线和特点,国内研究单位在CNT冷阴极分布式X射线源技术上的研究成果和应用情况。新鸿电子研制了焦点数量从7到256、阳极工作电流7~30 mA的数十个分布式X射线源产品,已经广泛应用于行包安检、工业无损检测、医疗诊断等领域,在三维透视成像中充分展示出静态结构、高检测速度、高时间和空间分辨率等优势,射线源的技术创新带动了成像系统的创新发展,具有广阔的研究和应用前景。

CNT冷阴极微焦点X射线管研制

以单根微米直径的碳纳米管(CNT)纱线为场致发射的电子源,通过Opera软件的模拟仿真进行阴极结构的设计,研制了基于CNT冷阴极,仅需静电聚焦实现微焦点,以金属管壳进行超高真空封装的小型闭管式微焦点X射线管。测试表明,单根直径50μm的CNT冷阴极电子源可以实现500μA的连续稳定电流发射;此时栅极控制电压V GC为886 V,对应的电场强度为1.77 V/μm,微型阴极的发射电流密度达到25.5 A/cm^(2)。金属封装的X射线管可以稳定工作于130 kV的阳极高压,通过调节聚焦电压,基于静电聚焦结构可实现45μm×58μm的焦点尺寸。研制的微焦点X射线管以50%的占空比工作,使用线对卡测试,分辨率达到了20 LP/mm,并对芯片等元件进行成像表征,内部微米级金线图像清晰。该微焦点X射线管可满足芯片、新能源电池等精密元件的无损检测需求,具有较好的应用前景。

基于碳纳米管的冷阴极X射线检测技术及其应用

针对热阴极X射线检测成像时存在的系统预热耗时长、寿命短、体积大、对外辐射剂量大等问题,提出采用碳纳米冷阴极X射线检测系统代替热阴极系统。冷阴极X射线管可通过栅极电压控制X射线管的管电流,具有良好的脉冲响应。本系统以具有场致发射特征的电子源制备成发射X射线源,配备平板探测器和可充电锂电池,建立区域无线网络,实现无线远程控制脉冲X射线源激发与平板探测器接收。利用该系统对耐张线夹、电力排管、焊缝内部缺陷进行检测研究。结果表明:该系统能够在计算机控制端即时成像,快速检出耐张线夹内部压接质量、电力排管内部氧化堆积物、焊缝内部气孔及裂缝缺陷等。利用该技术可大幅提高检测效率,对电力、石油管道、核电等领域的无损检测具有一定的应用价值。

冷热复合处理对CrN涂层结构及力学性能的影响

为了改善CrN涂层的塑性变形能力,通过增强阴极弧磁控溅射技术在316L不锈钢上制备了CrN涂层。利用管式炉和液氮对CrN涂层分别进行冷处理、热处理以及冷热复合处理。通过X射线衍射仪(XRD)、X射线光电子能谱仪(XPS)、扫描电子显微镜(SEM)以及纳米压痕仪表征涂层在后处理前后的微观结构、形貌特征、残余应力及力学性能。结果表明:经过后处理的CrN涂层硬度均有小幅度降低,但其塑性变形能力均提高。其中,先热后冷复合处理几乎保持CrN涂层硬度不变(仅降低0.7%),同时提高了其塑性变形能力(提高3.1%),增强了其韧性。

负电子亲和势材料及其在冷阴极中的应用

从20世纪60年代Ga As被首次发现具有负的电子亲和势起,负电子亲和势材料便被广泛地研究并应用于光电发射、二次电子发射以及冷阴极的制备中。相较于传统发射材料,负电子亲和势材料内部导带底高于表面真空能级,使得材料导带中的电子更易于从表面发射到真空中,因此该类型材料成为电子发射的理想材料。本文从定义、主要材料分类以及在冷阴极中的应用三个部分介绍了负电子亲和势材料,并对该材料应用的瓶颈和未来发展方向做了简要总结。

基于碳纳米管冷阴极的微焦点X射线源及其应用

碳纳米管(CNTs)场致发射源作为一种新的冷阴极电子发射源,能克服传统热阴极的缺点,基于CNTs冷阴极的微焦点X射线源的扫描成像系统可实现脉冲式发射、高速拍照、低剂量的特点,是一种可代替热阴极材料作为X射线管的核心阴极材料,目前在生物医疗、无损检测和科学研究等领域已经展现了巨大的应用价值,但在技术实现上CNTs阴极的可靠性、工作寿命和电流发射密度等仍存在瓶颈问题。本文回顾了微焦点X射线源的发展历史并介绍了CNTs冷阴极的制备工艺,展示了目前CNTs冷阴极的微焦点X射线源在工业和医疗领域取得的巨大成功,并结合实际的研究情况,探讨其发展中遇到的问题和未来的发展方向。

冷阴极电极质量改进实验研究

冷阴极电极作为冷阴极灯的核心组件,其质量的优劣对于灯的质量和寿命有直接的影响。为了提高冷阴极灯的品质,通过冷阴极电极以下的生产工艺进行实验研究:(1)改进钨杆清洗工艺;(2)采用无氧烧结玻珠。实验结果表明这些改进可以有效提高冷阴极电极的质量。

纳米金刚石的应用现状及发展前景

基于纳米金刚石在机械、化学、电子学等方面的优异特性,它在发动机的磨合油、部件表面的复合镀层、耐磨合金部件等领域得到了一定程度的应用。展望了纳米金刚石在精密抛光、塑料及橡胶材料、冷阴极场发射显示器等领域的应用。

纳米碳管阴极的场致发射显示研究

以热化学气相沉积法制备的多壁纳米碳管为场发射材料 ,采用一种简易的喷涂法将其制备为场发射阴极 .首先 ,将纯化后的纳米碳管与乙醇和丙酮溶液 (体积比为 9∶1 )进行混合 ;然后用喷枪将经过超声处理的悬浊液喷涂在具有ITO薄膜的玻璃基底上 ,制备了 30mm× 2 0mm大小的纳米碳管阴极 ,并进行了场致发射特性实验 ,制作了场发射显示板 .该二极结构的场发射开启场强为 3 2V/ μm ,发射电流密度可达 3A/m2 .此显示板具有稳定的发射电流和很高的亮度 。