电子轰击材料出气性能

固体材料在大气中会溶解、吸附一些气体,当材料置于真空环境下,就会因气体解溶、解吸、电子轰击等而发生放气。电真空微波器件广泛应用于加速器、卫星通信、可控热核聚变、全球定位及未来军事前沿的高功率微波武器等方面,其制造过程中非常关键的步骤是真空获得。为提高微波电真空器件研制过程中的管内真空水平,本文研制了高精度真空材料放气测试装置。系统采用小孔流导法测试出气率,极限真空低于5.0×10~(-7)Pa。利用本装置进行了电子轰击材料出气的试验研究。实验表明无氧铜在脉冲电子束轰击下出气速率与电压、频率、脉宽成正比;电子轰击的材料暴露大气后,在电子束轰击下出气速率在短时间内迅速降低到以前的放气率水平。采用四级质谱仪对电子轰击时真空室内的残余气体成分进行了分析,其主要成分为H_2(2),其它成份依次为H_2O(18),N_2(28),和CO_2(44)。对电子轰击材料出气机理进行了分析。金属电离规管进行的电子轰击除气实验研究也证明了这些实验结果。因此利用热阴极或电子枪作为电子发射源,对微波电真空器件收集极、阳极等金属材料进行电子轰击除气,将是制造长寿命高可靠微波电真空器件所必要且可行的方法。     

碳纤维复合石墨阴极的制备及电子发射性能

阴极作为强流电子束的起点，对高功率微波源的性能具有重要影响。石墨是高功率源用爆炸发射阴极的常用材料，具有高压重频条件下运行稳定和长寿命的优点。使用具有高长径比、低发射阈值的碳纤维对石墨阴极进行复合，采用场发射及高功率微波测试平台，对比分析纯石墨阴极及碳纤维复合石墨阴极的场发射性能、强流电子发射性能及输出微波特性，结合阴极的微观结构表征，研究碳纤维复合对石墨阴极电子发射性能的影响规律。研究表明：与鳞片石墨阴极相比，40%(质量分数)碳纤维复合石墨阴极的场发射阈值电场由143 kV/cm降低到119 kV/cm,降低了约16.8%,二极管电压为480 kV时输出的微波脉宽与峰值分别提高了13.5%,5.7%。同时考虑到碳纤维在爆炸电子发射过程中结构稳定性的特点，碳纤维的复合也有利于阴极使用寿命的提高。     

碳纤维复合石墨阴极的制备及电子发射性能EI

阴极作为强流电子束的起点,对高功率微波源的性能具有重要影响。石墨是高功率源用爆炸发射阴极的常用材料,具有高压重频条件下运行稳定和长寿命的优点。使用具有高长径比、低发射阈值的碳纤维对石墨阴极进行复合,采用场发射及高功率微波测试平台,对比分析纯石墨阴极及碳纤维复合石墨阴极的场发射性能、强流电子发射性能及输出微波特性,结合阴极的微观结构表征,研究碳纤维复合对石墨阴极电子发射性能的影响规律。研究表明:与鳞片石墨阴极相比,40%(质量分数)碳纤维复合石墨阴极的场发射阈值电场由143 kV/cm降低到119 kV/cm,降低了约16.8%,二极管电压为480 kV时输出的微波脉宽与峰值分别提高了13.5%,5.7%。同时考虑到碳纤维在爆炸电子发射过程中结构稳定性的特点,碳纤维的复合也有利于阴极使用寿命的提高。     

碳纤维复合石墨阴极的制备及电子发射性能EI北大核心

阴极作为强流电子束的起点,对高功率微波源的性能具有重要影响。石墨是高功率源用爆炸发射阴极的常用材料,具有高压重频条件下运行稳定和长寿命的优点。使用具有高长径比、低发射阈值的碳纤维对石墨阴极进行复合,采用场发射及高功率微波测试平台,对比分析纯石墨阴极及碳纤维复合石墨阴极的场发射性能、强流电子发射性能及输出微波特性,结合阴极的微观结构表征,研究碳纤维复合对石墨阴极电子发射性能的影响规律。研究表明:与鳞片石墨阴极相比,40%(质量分数)碳纤维复合石墨阴极的场发射阈值电场由143 kV/cm降低到119 kV/cm,降低了约16.8%,二极管电压为480 kV时输出的微波脉宽与峰值分别提高了13.5%,5.7%。同时考虑到碳纤维在爆炸电子发射过程中结构稳定性的特点,碳纤维的复合也有利于阴极使用寿命的提高。     

打拿极材料二次电子发射系数计算模型研究现状

电子倍增器使用寿命短的问题严重制约了其在导航定位系统中的应用,究其根本原因在于现有电子倍增器增益低,且打拿极材料在轰击能量较高的离子或较强电子束流长期作用下耐轰击能力弱,增益衰减过快。通过对国内外研究人员提出的打拿极二次电子发射系数计算模型进行详细分析,总结了这些模型的优缺点,提出建立打拿极材料二次电子发射系数计算模型的启示和建议。     

电子致放气测试装置的研究

材料表面吸附的气体分子在电子轰击作用下,会加速释放到真空系统中。为了测试在电子轰击下的材料放气特性,研制了一套电子致放气的测试装置。电子束发生器作为重要的组成部件,具有许多可调参数,这些参数会在一定程度上影响输出的电子束质量,进而影响电子致放气测试结果。文章首先通过实验测量了电子束斑和束流的影响因素,结果表明,聚焦电压和栅极电压对束斑的尺寸有直接的影响,而能量电压对电子束斑直径没有影响。此外,阴极电压、电子能量和栅极电压都可影响到发射电流,从而影响出射的电子束电流。为了验证装置的电子致放气测试能力,采用放气率很低的316 L不锈钢作为测试样品,比较测试其经过三次电子束轰击前后的放气特性。结果表明,经过除气的316 L不锈钢的电子致放气率可较明显地测定,且电子束轰击下放气的主要成分由N₂/CO变为H₂。     

高功率微波源用阴极材料的研究现状

高功率微波(High power microwave,HPM)技术中最关键的技术是阴极材料技术,阴极材料的性能决定着高功率微波的输出功率.综述了目前所用的阴极材料的研究现状,主要分析对比了几种爆炸发射阴极材料的发射机制以及优缺点:以尖端场增强为发射机制的金属阴极由于熔点低、等离子体闭合速率快等问题,在高功率微波源技术中的应用受到了限制;天鹅绒的发射机制为表面闪烙点火,最大的缺点是阴极寿命短;碳纤维阴极不仅有尖端处的场发射,而且存在侧面的表面闪烙过程,高重复频率及长寿命的碳纤维阴极是目前研究的热点,热电离阴极发射电流密度有待提高;铁电阴极在HPM源中极具发展潜力.     

XPS谱仪铝靶的制作方法

光电子能谱仪都是用标准的铝特征谱线Al_(ka1,2)作为激发源。通常用能量5～20kV的电子束轰击靶表面来产生特征x射线。在电子轰击下,绝大部分能量转变成热能,因此,要求靶基体材料的导热性好。由于铝的热传导性较差,所以铝靶不能用整块铝材来制造,只能用镀膜方式,即在无氧铜的基体上覆盖一层铝膜,来改善靶的导热性。由此,要求覆盖层与     

强流微束斑电子束系统的研究和设计计算

本文研究了强流微束斑电子束的形成问题。提出了一种采用新型磁透镜的电磁复合聚焦系统，这种新型电子束系统的轴上磁场在电子束束腰附近达到极大值，并且轴上磁场分布关于其极大值不对称。利用附加电极在磁场较强的区域构成具有拒斥电场的电透镜，以充分抑制空间电荷推斥力的散焦作用。利用描述电流密度分布演化的变态伏拉索夫方程，研究了强流微束斑电子束系统，数值分析研究了透镜激励和电子束初始条件对于电流密度分布演化的影响。发现侧极靴透镜和相应电极形成的电磁复合聚焦场对于强电流电子束具有优秀的聚焦效果，设计出了利用侧极靴磁透镜的新型电子光学系统，这种系统可以形成电流达到1．96mA、束斑半径仅为4．2μm的强电流微束斑电子束。     

几种高功率微波介质窗材料的研究综述

高功率微波介质窗的击穿问题已成为高功率微波武器发展的一个技术瓶颈,选择适当的介质材料、提高窗的抗击穿能力是解决此问题的一条重要途径.总结了国内外主要研究机构使用的高功率微波介质窗材料类型及特性,对各自优缺点进行比较分析,并给出了分析结论.     

Subnanosecond 1-GW pulsed 38-GHz radiation source

The regime of excitation of subnanosecond high-power microwave pulses has been studied in a Cherenkov device with an extended periodic slow-wave structure, using an electron beam from a compact pulsed high-current electron accelerator (290 keV, 2.3 kA, 1 ns). Conditions are established for which the power conversion coefficient can reach up to 1.5 at an output pulse power of 1.2 GW and a pulse duration of 200 ps.     

Electron beam deposition system causing little damage to organic layers

Conditions for deposition of an aluminum (Al) layer on an organic light-emitting layer with an electron beam (EB) deposition system were optimized with respect to deposition rate and damage to organic layers. The damage to the organic layers was found to be mostly caused by X-rays emitted from a target bombarded with accelerated electrons. In order to decrease the X-ray intensity while maintaining a high deposition rate, we used an EB source which emits high-density EB at low acceleration voltage. In addition, we inserted a heat reflector and a sintered-carbon liner between the Al target and copper crucible to improve heat insulation. As a result, the voltage needed for the deposition of Al electrodes at a rate of about 8 nm/s was lowered from normal voltages of 2.0 kV or higher to as low as 1.5 kV. To reduce the number of electrons hitting the substrate, we set pole pieces near the target and an electron trap in the chamber. The devices on which Al electrodes were deposited with the EB system showed almost the same properties as those of devices on which the Al electrodes were deposited by a resistive-heating method.     

Low-loss electron beam transport in a high-power, electrostatic free-electron maser

At the FOM Institute for Plasma Physics “Rijnhuizen”, The Netherlands, the commissioning of a high-power, electrostatic free-electron maser is in progress. The design target is the generation of 1 MW microwave power in the frequency range 130–260 GHz. The foreseen application of this kind of device is as a power source for electron cyclotron applications on magnetically confined plasmas.

The device is driven by a high-power electron beam. For long-pulse operation a low loss current is essential. A 3-A electron beam has been accelerated to energies ranging from 1.35 to 1.7 MeV and transported through the undulator at current losses below 0.02%. Further, it was shown that the beam line accepts an electron energy variation of 5% with fixed beam optics. This is essential for rapid tuning of the microwave frequency, over 10%.

Electron beam simulations have shown to be remarkably accurate both for the prediction of the lens settings and for the intercepted current. The operational settings of the beam line which give the highest current transmission are within a few percent of the simulated values.     

The Coloration of a Benzospiran Compound due to an Electron Bombardment

1,3,3-Trimethylindolino-6’-nitrobenzopyrylspiran (spiran) in a polymcr matrix is reversibly changed to two coloured spccies by an electron beam bombardment (cathodochromism). It is similar to photochromism. The major species due to the bombardment appears to be the same as the photoproduct. The other is produced only by the bombardment and is closely related to the polymer. Unlike the case of photoreaction, all components of the specimen are affected by bombarded electrons. Therefore the minor product is thought to be formed by a rcaction between the major one and a compound liberated from the matrix; moreover it is more stable than the major one. Owing to the formation of the minor product, the spiran-polymer matrix system is not. Suitablw for an erasable and reusable electron beam recording medium, but it is rather promising for permanent rccording use.     

Flash X-ray radiography source based on plasma-filled rod pinch diode

Results of experiments on the formation of a high-power focused electron beam in a plasma-filled rod pinch diode driven by a high-current MIG generator (maximum voltage, 1.3 MV; impedance, 0.65 Ω) are presented. The proposed diode with a sharpened 1.5-mm-thick tungsten rod anode provides an X-ray source for flash radiography with a size of ∼1 mm, which is capable of producing a radiation dose of 2.4 rad per pulse at a distance of 1 m. The results of comparative experiments with and without plasma injection into the diode are presented.     

Measuring the virtual cathode velocity

An electron beam with a virtual cathode (VC) transported in a two-section drift tube of a SINUS-7 high-current electron accelerator has been studied. The dependence of the VC velocity on the injected current has been experimentally determined for the first time. It is established that the VC motion in the drift tube is accompanied by microwave oscillations, which are caused by transient processes involved in the formation of a compressed electron beam.     

Multiple ionization of vacuum-arc-generated metal ions in a magnetic trap heated by high-power microwave radiation

We present experimental deta on the multiple ionization of refractory metal ions formed in the vacuum-arc discharge plasma, which is achieved by injecting plasma into a magnetic trap and additionally heating it by high-power microwave radiation in the millimeter range. An increase in the high-power microwave source (gyrotron) frequency from 37.5 to 75 GHz allowed plasma of greater density to be heated to a sufficiently high electron temperature ensuring the multiple ionization of trapped particles. In the case of platinum, the microwave heating led to an increase in the average ion charge from 2 to 7, while the maximum platinum ion charge reached 10 and the total ion beam current amounted to 300 mA.     

Electron entrainment current in gases bombarded with beams of fast highly-charged ions

It is shown that asymmetry in the ejection of electrons in an elementary collision event between an atom and a fast highly-charged ion may lead to a macroscopic effect, the electron entrainment current, when a gas target is bombarded by a beam of fast highly-charged ions. The entrainment current is calculated for the bombardment of a helium target by a 25 MeV/u Mo⁴⁰⁺ beam. Pis’ma Zh. Tekh. Fiz. 24, 62–65 (September 26, 1998)     

耦合腔行波管多级降压收集极的模拟设计

本文中较全面地讨论了多级降压收集极的物理模型.通过分析3个工作频率点高频输出端的电子注特性来设计多级降压收集极:借助电子注层流性参量,对带有再聚焦磁场的散群聚区进行优化,得到磁场参量的初始值;运用电子轨迹等效电位图,确定各电极的初步电位,通过收集极区结构和电极电位的优化得到较高的收集极效率;通过收集极的全面优化使收集极效率得到了进一步的提高;在考虑二次电子发射情况下,对收集极结构和电极电位进行优化,在保证收集极效率的情况下使二次电子回流率为零.模拟结果表明:借助电子注层流参量设计出带有再聚焦磁场的散群聚区使电子轨迹层流性得到较大改善;合理的结构和电极电位能得到较高的收集极效率;二次电子发射对收集极效率影响较大,合理的调节外凸锥形电极的倾角能避免二次电子回流.此设计运用于一耦合腔行波管收集极的模拟计算,达到了良好的效果.     

A relativistic backward wave oscillator with a modulating resonance reflector

A high-efficiency relativistic microwave source based on a backward wave oscillator (BWO) with a resonance reflector has been studied by experimental and numerical methods. The BWO is capable of generating 12-ns pulses with a carrier frequency of 9.93 GHz at an output radiation power of 0.75 ± 0.11 GW. For the BWO pumped by a high-current electron beam from a SINUS-6K accelerator, the regime with relatively high pulse-to-pulse stability is characterized by a 40% efficiency of power conversion.