真空强场环境耐电子轰击材料优选研究

发布时间：2018-12-19 13:58

【摘要】：相对论返波管(RBWO)具有高功率、高效率、适合重复频率工作等特点,是目前最有发展潜力的高功率微波(HPM)器件之一。然而,强电磁场真空击穿引起的输出微波功率下降、脉宽缩短以及结构损伤带来的寿命等问题,严重限制了RBWO的输出能量,影响了其实用化进程。本论文基于“阳极”击穿模型,开展了耐电子轰击材料的优选研究。论文的研究成果如下:(1)结合经典Monte-Carlo方法和Bethe能量损失规律,研究了MeV级电子垂直入射Cu、SS304和TA2三种常见金属靶材的能量损失规律。研究表明,材料原子序数和原子密度越小,电子在材料中的有效射程越长,单位体积内沉积的平均能量越低,越有利于材料耐受高能电子轰击。综合金属材料达到熔融烧蚀的临界条件,给出了耐电子轰击材料优选原则:密度小、熔点高和比热容大。(2)采用环形电子束打靶实验比较了Cu、SS304和TA2三种材料的耐电子轰击性能,在相同的电子束能量下,Cu因密度高、熔点低和比热容小而更容易受到电子束轰击破坏。相对而言,密度低、熔点高和比热容大的TA2材料具有更好的耐电子束轰击性能。实验结果初步验证了耐电子束轰击材料的优选原则。(3)采用CST软件模拟设计了场强1.8 MV/cm的波导测试腔,单个腔内两侧场分布非对称,以将材料的电子发射和轰击性能分开研究,进一步明确“阳极”机制引起的强电磁场真空击穿模型。在1 T外加引导磁场下,SS304材料测试腔强电磁场真空击穿可以将脉宽由25.2 ns缩短至15.6 ns,缩短约38%,输出微波功率由2.06 GW减小至1.78 GW,减幅约13.6%。与SS304材料相比,轰击侧采用耐受电子轰击的TA2材料可以将脉宽提高约3.8 ns,功率增加约0.14 GW。(4)在1 T外加引导磁场下,整腔钛材料与SS304材料相比,TC18性能最佳,可以将脉宽由15.6 ns增加到24.8 ns,功率由1.78 GW增加到2.04 GW,实验结果表明,耐电子束轰击性能更优的钛材料,可以有效缓解强场真空击穿引起的脉宽缩短和功率下降等问题。其优异性能是由于存在的α相晶粒细小能够强化晶体结构,延缓裂纹形核,提高了TC18材料的耐电子轰击性能;同时,发射性能也有所改善。本论文在理论分析和数值计算的基础上,给出了强场真空环境下耐电子轰击材料的优选原则,相关研究结果可为RBWO结构中的材料优选提供支撑,同时可为RBWO中强电磁场真空击穿机理分析提供一定参考。
[Abstract]:Relativistic backward-wave tube (RBWO) is one of the most promising high-power microwave (HPM) devices due to its high power, high efficiency and suitable repetition rate. However, the output microwave power is decreased, the pulse width is shortened, and the lifetime caused by structural damage is reduced due to the vacuum breakdown of strong electromagnetic field, which seriously limits the output energy of RBWO and affects its practical process. Based on the anodic breakdown model, the selection of electronic bombardment resistant materials is studied in this paper. The research results are as follows: (1) combined with the classical Monte-Carlo method and the Bethe energy loss law, the energy loss laws of three common metal targets, Cu,SS304 and TA2, are studied. The results show that the smaller the atomic number and density, the longer the effective range of electrons in the material, and the lower the average energy deposited in the unit volume, which is more favorable to resist the high-energy electron bombardment. In order to meet the critical condition of melting ablation, the optimum selection principle of electron bombardment resistant materials is given: low density, high melting point and high specific heat capacity. (2) Cu, is compared with ring electron beam shooting experiment. Under the same electron beam energy, SS304 and TA2 are more vulnerable to electron beam bombardment because of their high density, low melting point and low specific heat capacity. Comparatively speaking, the TA2 materials with low density, high melting point and high specific heat capacity have better resistance to electron beam bombardment. The experimental results preliminarily verify the principle of optimal selection of materials resistant to electron beam bombardment. (3) the waveguide test cavity with a field strength of 1.8 MV/cm is designed by using CST software, and the field distribution on both sides of a single cavity is asymmetric. In order to study the electron emission and bombardment performance of materials separately, the vacuum breakdown model of strong electromagnetic field caused by "anode" mechanism is further clarified. At 1 T external magnetic field, the vacuum breakdown of SS304 material with strong electromagnetic field can shorten the pulse width from 25.2 ns to 15.6 ns, and the output microwave power from 2.06 GW to 1.78 GW,. Compared with SS304 material, the pulse width of TA2 material with electron bombardment resistance can be increased by about 3.8 ns, power by 0.14 GW. (4). Compared with SS304 material, the whole cavity titanium material has the best performance compared with SS304 material under 1 T external guiding magnetic field. The pulse width can be increased from 15. 6 ns to 24. 8 ns, power from 1. 78 GW to 2. 04 GW,. The experimental results show that the titanium material with better resistance to electron beam bombardment can be obtained. It can effectively alleviate the problems of shortening pulse width and decreasing power caused by strong field vacuum breakdown. The excellent properties are that the fine 伪 phase grains can strengthen the crystal structure, delay the nucleation of cracks, and improve the electron bombardment resistance of TC18 materials, and the emission properties are also improved. On the basis of theoretical analysis and numerical calculation, this paper presents the optimal selection principle of electron-resistant materials in strong field vacuum environment. The related research results can provide support for material selection in RBWO structures. At the same time, it can provide some reference for the analysis of vacuum breakdown mechanism of RBWO.
【学位授予单位】：湘潭大学
【学位级别】：硕士
【学位授予年份】：2017
【分类号】：TN125

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