真空密封透射式微型微束调制X射线源

发布时间：2019-05-25 01:50

【摘要】：空间X射线通信作为“下一代新的空间通信方法”,得益于方向性好、发射功率低、传输距离远、保密性强、不受空间环境电磁干扰、通信频带宽,有着广泛的应用前景,可大大改善空间通信频率资源越来越紧张的现状。调制X射线源作为空间X射线通信中的关键部件,它的调制速率、焦斑尺寸将直接影响X射线的通信速率、通信距离,故研制低功耗、小体积、小焦斑、高调制速率的调制X射线源对验证X射线通信技术及最终实现空间通信起着至关重要的作用。本论文的主要研究内容就是开展对真空密封的透射式微型微束调制X射线源的理论分析、物理建模、仿真优化、方案设计、关键技术攻关、特殊工艺探索,并完成系统的样机研制及性能测试。具体研究内容及主要成果如下:采用SIMION软件不断优化完善栅极结构,仿真实现了栅极-0.6V~+0.6V的低电压调制,调制电压幅值减小了近一个数量级,易于实现X射线的高频调制,从而提高X射线的通信速率;对三个静电聚焦电极进行电子运动学的仿真优化,得到了150μm的焦斑尺寸,打破了热阴极难于聚焦成微米焦斑的技术瓶颈,为空间X射线的远距离通信奠定基础;利用MCNP软件的仿真优化,得到透射式阳极靶在不同阳极靶材、不同电子能量下的最佳靶厚,改善了反射式阳极靶出射X射线强度小的问题,有助于提高X射线的调制频率;为改变常规的化学镀膜工艺或真空镀膜工艺效果不理想,镀层质量差的现状,探索了Be窗清洗、置换锌层工艺和高真空离子溅射工艺;借鉴真空灭弧室的封口和排气同时进行的一次封排工艺,实现了对调制X射线源的全真空密封,管内真空度高于10-3Pa,解决了半真空X射线管工作时需放入真空腔的问题;完成了原理样机的研制,验证了调制X射线源的栅极幅值调制和脉冲调制。相较之前的调制X射线源,本文的创新性成果主要体现在以下四方面:攻关了调制X射线源的栅极-0.6V~+0.6V的低电压调制技术,并通过了实验验证,使得X射线的高频调制成为可能;采用三个静电聚焦电极提高对电子束聚焦能力,仿真实现了150μm的微焦斑尺寸;实现了调制X射线源中多个部件及整管的高真空密封,且真空密封性良好,现已保持管内真空度高于10-3Pa两年以上;首次发现了MHz级栅极脉冲频率对X射线强度的显著影响。所研制的调制X射线源由热阴极电子发射系统、栅极调制、静电聚焦和透射式阳极靶四部分组成,它集成了电子束聚焦和栅极调制功能,通过仿真得到了150μm的微焦斑尺寸,实现了栅极-0.6V~+0.6V的低电压调制,是目前国际上最新的基于热阴极的全真空密封的调制X射线源,为我国验证远距离、高速的空间X射线通信提供技术支持。
[Abstract]:As the "next generation new space communication method", space X-ray communication has a wide application prospect because of its good directivity, low transmission power, long transmission distance, strong confidentiality, no electromagnetic interference from space environment and wide communication band. It can greatly improve the increasing shortage of space communication frequency resources. As the key component of space X-ray communication, the modulation rate and focal spot size of modulation X-ray source will directly affect the communication rate and communication distance of X-ray, so the development of low power consumption, small volume and small focal spot will be developed. The modulation X-ray source with high modulation rate plays an important role in verifying X-ray communication technology and finally realizing space communication. The main research content of this paper is to carry out the theoretical analysis, physical modeling, simulation optimization, scheme design, key technology research and special process exploration of the transmission micro-beam modulation X-ray source of vacuum seal. The prototype development and performance test of the system are completed. The specific research contents and main results are as follows: using SIMION software to optimize and perfect the gate structure, the low voltage modulation of gate-0.6V is realized by simulation, and the amplitude of modulation voltage is reduced by nearly one order of magnitude. It is easy to realize the high frequency modulation of X-ray, so as to improve the communication rate of X-ray. The electronic kinematics of the three electrostatic focusing electrodes is simulated and optimized, and the focal spot size of 150 渭 m is obtained, which breaks the technical bottleneck that the hot cathode is difficult to focus into the micron focal spot, and lays the foundation for the long-distance communication of space X-ray. By using the simulation and optimization of MCNP software, the optimum target thickness of transmission anode target under different anode target and different electron energy is obtained, which improves the problem of low X-ray intensity of reflective anode target and helps to improve the modulation frequency of X-ray. In order to change the effect of conventional chemical plating process or vacuum coating process and the poor quality of coating, Be window cleaning, zinc replacement process and high vacuum ion sputtering process were explored. Referring to the sealing process of vacuum interrupter and exhaust at the same time, the full vacuum sealing of modulation X-ray source is realized, and the vacuum degree in the tube is higher than 10 脳 3PA, which solves the problem that the semi-vacuum X-ray tube needs to be put into the vacuum cavity when it works. The prototype is developed, and the gate amplitude modulation and pulse modulation of the modulation X-ray source are verified. Compared with the previous modulation X-ray sources, the innovative results of this paper are mainly reflected in the following four aspects: the low voltage modulation technology of gate-0.6V ~ 0.6V for modulating X-ray sources is studied and verified by experiments. It makes the high frequency modulation of X-ray possible. Three electrostatic focusing electrodes are used to improve the focusing ability of electron beam, and the microfocal spot size of 150 渭 m is simulated. The high vacuum seal of many components and the whole tube in the modulation X-ray source has been realized, and the vacuum sealing property is good, and the vacuum degree in the tube has been kept higher than that of 10-3Pa for more than two years. It is found for the first time that the MHz gate pulse frequency has a significant effect on the X-ray intensity. The modulation X-ray source is composed of four parts: hot cathode electron emission system, gate modulation, electrostatic focusing and transmission anode target. It integrates electron beam focusing and gate modulation functions, and the microfocal spot size of 150 渭 m is obtained by simulation. The low voltage modulation of gate-0.6V ~ 0.6V is realized. It is the latest fully vacuum sealed modulation X-ray source based on hot cathode in the world at present, which provides technical support for the verification of long-distance and high-speed space X-ray communication in our country.
【学位授予单位】：中国科学院国家空间科学中心
【学位级别】：博士
【学位授予年份】：2017
【分类号】：TN92

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