真空规管对低温容器残余气体影响的实验研究

以高真空多层绝热低温容器为研究对象,利用残余气体分析仪研究冷阴极真空规管、热阴极真空规管以及热阴极真空规管不同放置位置对低温容器真空夹层内残余气体的影响.结果表明:冷阴极真空规管对低温容器真空夹层内残余气体的影响几乎是可以忽略不计的;热阴极真空规管对低温容器真空夹层内残余气体的影响较大,热阴极的灯丝和残余气体之间存在化...     

碳纳米管阴极强流脉冲发射放气质谱分析

借助2 MeV直线感应加速器注入器平台,利用四极质谱仪研究了碳纳米管阴极的强流脉冲发射放气质谱特性. 研究结果表明:在脉冲高压电场下,碳纳米管阴极材料释放出较多的吸附气体,解吸气体又以CO₂,N₂(CO),H₂三种气体居多,这些解吸气体在阴极等离子体形成过程中起着重要的作用. 通过分析解吸气体成分的含量,证明碳纳米管阴极强流脉冲电子发射过程为场致等离子体发射,而不是场致爆炸发射. 关键词： 碳纳米管阴极 强流脉冲发射 质谱分析 场致等离子体发射     

大电流碳纳米管场发射阴极研究

报道了在较大发射面积上获得较大场发射电流的碳纳米管场发射阴极。为了加强场发射电流,在丝网印刷浆料中增加一种金属纳米颗粒,金属颗粒增强了碳纳米管发射体和衬底的接触,提高碳纳米管和衬底的粘附作用。利用改进后的丝网印刷方法制备了大电流碳纳米管场发射阴极,测得最大发射电流为68.0 mA,阴极有效发射面积约1.1 mm2,发射电流密度约6.2 A/cm2;并成功将改进方法制备的大电流场发射碳纳米管阴极应用于场发射真空器件原型。实验证明这种具有较大发射电流和较大发射电流密度的场发射能够满足部分大功率电子器件的需求。收稿日期:; 修订日期:     

气体传热对多层绝热性能影响的试验研究

文中通过建立的能进行夹层气体置换的稳态量热器试验系统,试验分析了夹层气体传热对多层绝热材料有效热导率的影响,重点对置换气体种类、气体压强、材料层数及冷热边界温度对多层材料的影响进行试验研究。试验表明在10—60层/cm层密度范围,真空度低于100Pa时,Kn数属于自由分子状态区域和中间压强区域,此时材料的有效热导率随残留气体热适应系数的增大而减小,并随着真空度的降低而增大,当残留气体为空气时,为保证多层材料的绝热性能,应尽量维持真空度不低于10-2Pa。同时,分析表明为有效降低低真空下稀薄气体传热对多层绝热性能的影响,可以采用综合热适应系数较低的气体置换夹层中的空气,以减少低真空多层绝热材料的有效热导率,改善绝热性能。     

Investigation of unstable motion characteristics of vacuum arc cathode spots between transverse magnetic field contacts

With the improvement of the current level of power grids, the requirements of the opening level of the vacuum switches are also increasing. Vacuum arc cathode spots provide steam and electrons and, to a certain extent, determine the opening capacity of the vacuum switch. In this paper, a vacuum arc cathode spot research platform based on the de-mountable vacuum chamber is constructed. The characteristics of the vacuum arc cathode spots under the transverse magnetic field (TMF) contacts are assessed by a high-speed charge coupled device. The experimental results show that the cathode spot diffusion process can be divided into three processes through cathode spot distribution, arc voltage and current: initial diffusion stage of cathode spots, unstable motion stage of cathode spots, and extinguishing stage. The motion mode of cathode spots during unstable motion stage can be divided into cathode spots group stagnation (CSGS) to multi-cathode jet (MCJ) switch mode, cathode spots group motion (CSGM) to MCJ switch mode, CSGM mode, and MCJ mode. The effects of peak current and contact diameter on unstable motion mode were analysed.     

碳纳米管阴极的强流脉冲发射性能研究

采用丝网印刷和涂敷方法制备了两种碳纳米管阴极，并研究了两种阴极的强流脉冲发射特性，表征了阴极表面碳纳米管的形貌及分布.研究结果表明在脉冲宽度为100 ns、电压为1.64×10⁶ V的脉冲电场下，涂敷法制备阴极的场发射电流最高达5.11 kA，最高发射电流密度达260 A/cm².丝网印刷法制备阴极的场发射稳定性优于涂敷法制备阴极，但其发射电流低.阴极表面发射体的形貌与分布影响了阴极的脉冲发射性能.碳纳米管阴极的脉冲发射机理为爆炸电子发射.碳纳米管阴极可以作为强 关键词： 碳纳米管 阴极 脉冲发射 强电流     

一种新型二维X射线探测器

本文建立一种新型X射线探测器,它是一种矩阵寻址方式的二维探测器,由两块玻璃基板组成,分别称作阴极板和阳极板,阴极板内侧镀有行电极和X射线阴级（例如CsI),阳极板上有寻址电极,障壁,两块基板对位封接,使行电要与寻址电极互相垂直,封接后先抽高真空,然后充入氩气与CO2混合气体,本探测器具有薄,轻,图象无畸变并可以利用PDP显示器件的工艺制作大尺寸器件及大量制造等优点。     

两步化学沉积法制备ZnO薄膜及其场发射特性

在低温常压条件下,以ITO玻璃为衬底,采用电化学法与湿化学法结合的两步化学沉积法制备了团簇状ZnO薄膜。利用XRD,SEM分析了薄膜结构和表面形貌,并采用二极管结构在高真空条件下对薄膜进行了场发射性能测试。稳定发射后,开启电场为3.0 V/μm。当电场为5.8 V/μm时,电流密度为583.3 μA/cm²。研究表明:两步化学沉积法低温制备ZnO薄膜是可行的,且该薄膜具有良好的场发射性能。     

Dielectric Recovery of Vacuum Arcs after Strong Anode Spot Activity

Recovery of dielectric strength and post-arc currents after diffuse and constricted vacuum arcs were measured for filat OFHC-Cu contacts (D = 25 mm, d = 7.5 mm) enclosed in a bakable UHV chamber. The arc current pulse had a trapezoidal shape of 5.5-ms duration with peak values up to 11 kA. In comparison with the fast recovery of diffuse arcs, the recovery of constricted arcs with gross melting is considerably retarded. Post-arc currents are simulated using the Andrews-Varey model extended to include the effects of secondary electron emission due to ion bombardment of the cathode and loss of the plasma due to thermal motion. The flow of charge carriers to the anode and the shield, which is at the anode's potential, are registered separately. The amount and decay of the residual plasma is evaluated from the measurements of post-arc current. The decay times of a few tens of a microsecond give evidence of ions with energies below 1 eV. The origin and effect of slow ions on recovery is discussed.     

Field emission pressure sensors with non-silicon membranes

We report on the fabrication of cold cathode emitter and the design parameter simulation of a functional field emission-based pressure sensor. This device comprises a membrane made of metallic compound acting as the anode in front of a flat cold cathode emitter. First, the mechanical deflection of a diaphragm under selected input pressures is modeled. The current density distribution in the deflected diaphragm is then calculated using realistic field emission characteristics from fabricated sulfur doped boron nitride (S-BN) cold cathode device. The total current output was found by integrating the measured current density of the fabricated electron emitter device over the entire diaphragm area of the membrane as function of external pressure. The results show that conventional silicon membranes would pose problems when implemented in a real field emission device, and show how the use of unconventional materials (i.e., TiN) can help overcome these problems.     

碳纳米管阴极强流脉冲发射放气特性研究

为了研究碳纳米管(CNT)阴极强流脉冲发射特性, 在2MeV直线感应加速器(LIA)注入器平台上开展了阴极放气特性实验. 研究结果表明：碳纳米管阴极强流发射时伴随有严重的阴极放气, 阴极放气参与形成阴极等离子体. 对于特定的几次实验, 通过数值积分估算了阴极材料的放气量为0.8—1.12Pa·L, 释放的气体分子数目与电子数目之比为254—203, 说明阴极等离子体为弱电离等离子体. 分析了二极管电压、发射电流密度、放气量以及放气分子数目/电子数目之间的关系     

钛基纳米金刚石涂层场发射阴极

设计了一种新的金刚石场发射阴极工艺.用旋涂法在金属钛片上涂覆纳米金刚石涂层，经过适当条件的真空热处理，实现钛与金刚石之间的化学键合即欧姆接触，从而形成以金属钛为衬底，碳化钛键合层为过渡层，金刚石纳米颗粒为场发射体的场发射阴极.样品的阈值场强可达6.3V/μm，场发射电流密度在21 V/μm场强下可达到60.7 μA/cm2.提出了样品的结构模型,并分析了其电子输运方式.样品的Fowler-Nordheim曲线基本为一直线，根据经典场发射理论，可以证实其电子发射机制为场发射.观察到在获得稳定的场发射性能之前存在激发过程，并对其作了简单解释.     

Field evaporation end forms of tungsten

The anomalous field ion images consisting of bright bands of variable width parallel to the 〈111〉 zones, previously reported for tungsten pulse evaporated in helium at 78 K, have also been observed with neon as imaging gas. For both gases the upper limit to the pulse lengths for production of the bands is about 1 ms. The influence of the ratio, R, of pulse height to the total evaporation voltage on the intensity distribution in field ion images of tungsten has been studied for helium and neon together with the effect of residual gases peculiar to ion pumped stainless steel UHV systems (H₂, CH₄ and CO). It is found that when R is raised to a certain level traces of residual gases if present in sufficient quantities, can produce, with tungsten, images with intensity distributions similar to those found with molybdenum after slow evaporation. These are attributed to preferential adsorption of the residual gases on different parts of the specimen and, depending on the nature of the adsorbate, leading to a promotion or a reduction of the ionization probability of the imaging gas. It is pointed out that before an image can be described as typical of a particulaelement or alloy, the conditions of prior evaporation should be carefully controlled.     

潘宁放电在密封电真空器件真空度测量中的应用

 密封电真空器件的可靠性尤其重要，而影响其可靠性的主要因素是真空度。对于具有两个电极的密封电真空器件由于无法利用其自身的电极结构直接测定其真空度，因此需要研究并建立一种合适的真空度测量方法。分析了利用潘宁放电来测量两个电极的密封电真空器件真空度的工作原理，设计了测试实验装置，初步建立了密封电真空器件的潘宁放电模型，给出了有关实验数据。     

LaB6与TaC混合涂层热阴极

研究了一种LaB6与TaC混合涂层热阴极,其发射层通过均匀混合LaB6与TaC粉末得到。比较了该阴极在LaB6与TaC混合比例为1∶1, 2∶1和3∶1下的发射特性,发现混合型LaB6阴极的功函数与多晶LaB6阴极的非常接近,在3∶1的混合比例下,电极的发射电流稳定,得到的电流密度为30 A/cm2。该电极可被应用于需要大电流密度和超大面积阴极的真空电子器件及动态真空电子束设备中。     

大直径钪酸盐阴极发射特性

 为获得kA级热发射电子束,研制了直径为100 mm钪酸盐热阴极组件,并建立了适应大面积热阴极实验环境的2 MV 注入器试验平台。实验在二极管真空3.7×10^-5 Pa、二极管电压1.95 MV、脉宽120 ns（FWHM）、阴极温度1 120 ℃时,获得最大收集电流1 038 A,发射电流密度约13 A/cm²。实验结果表明,工作状态下阴极发射能力与激活温度、系统真空度关系密切。     

被羰基镍污染的CO气体在Cu(111)表面的近常压吸附研究

本文利用近常压X射线光电子能谱和近常压扫描隧道显微镜研究了在超高真空(UHV)和近常压条件下,被羰基镍污染的CO气体在Cu(111)表面的吸附过程. 通过控制被污染CO的气体压力,可以在Cu(111)表面上形成Ni-Cu双金属催化剂. 此外,本文探索了CO在所形成的Ni-Cu双金属表面上的吸附和解离过程,并报道了几种CO的高压吸附相结构.     

Über die Lebensdauer von elektrischen Gleichstrombögen im Ultrahochvakuum

The life time of de-arcs in vacuum was found to be determined by thin film effects on the cathode surface. By removal of surface contaminations in UHV the average arc duration was greatly enhanced. A further enhancement occurs by deposition of clean metal films. This is demonstrated for Mo on Cu-cathodes, and for Cu on Mo-cathodes. Hence compound materials like MoCu show an extreme high arc duration. The vapour pressure of the cathode material, however, has a minor influence. Therefore an arc between MoCu-electrodes emits more Mo- than Cu-vapour, as it is shown by mass analysis. Measurements of dc-field emission from arc cathodes (after the arc) show that the arc life time is correlated to the stability of field electron emission. The most intense field emitting sites are produced during the ignition of the arcs.     

天鹅绒阴极脉冲放气及重复频率运行真空特性

为获得天鹅绒阴极加电运行时的放气信息,在加速器Torch-02(电压约300 kV、脉宽约6 ns、电阻约100Ω、频率1~300 Hz)上开展了单次及重复频率下的真空兼容性实验研究。对于发射面积为28 cm2、阴阳极间距50 mm、有效抽速62 L/s、容积为4.6 L的真空二极管-天鹅绒阴极系统,根据不同电流发射密度时的气压历史曲线,确定了单位面积上天鹅绒表面中性气体释放数目与脉冲能量的关系。通过实时记录不同频率下的气压演化,在本底气压约5×10-3Pa、单脉冲能量约6 J条件下,得到了平衡压强与重复频率的变化关系:10~100 Hz时,平衡压强与重复频率近似呈线性递增;超过100 Hz时,真空恶化明显,气压随频率呈超线性增长,300 Hz时平衡压强已升至Pa量级。最后,针对重复频率运行时的放气特点,讨论了一种"分布式"抽气思想以改善系统有效抽速。     

The effects of residual gases on optical constants of Al films

Using the attenuated total reflection technique, the effects of residual gases on optical constants of Al films have been investigated in situ during and after growth of films. It has been found that the optical constants of Al films are strongly affected by residual gases even under ultrahigh vacua (UHV) in the order of 10⁻⁶ Pa. In order to explore the origin of a variation in optical constants produced by the residual gases, the optical constants of Al films exposed to oxygen, nitrogen or hydrogen gases have been measured.