脉冲放电激励氧碘化学激光的数值模拟

发布时间：2018-05-04 19:08

本文选题：氧碘化学激光器 + 脉冲放电　；参考：《大连理工大学》2015年硕士论文

【摘要】：脉冲氧碘化学激光器(COIL)与连续波氧碘化学激光器(CWCOIL)相比,不仅具有连续波氧碘化学激光器的优势,而且自身还具有很多独特的优势,如激光所能穿透的深度更深、速度更快；具有较高能量的脉冲激光能够进行高效率的拉曼频移,使激光的波长具有可变动性等。由于这些优势的存在,吸引了美国、俄罗斯、中国、日本等众多国家的科研人员从事相关方面的研究。实现氧碘化学激光脉冲化的方法有很多,其中脉冲放电瞬间产生碘原子是最有发展前景的一种激光脉冲化技术。然而,到目前为止相关的实验研究基本上都局限在不同条件下对外部参量的观测上,缺乏对产生脉冲激光的关键环节的研究,这使得人们在实验时存在一定的盲目性。与实验研究工作相比,相关的理论模拟工作非常少,在国外,目前见到的唯一报道是近年Kochetov等人的工作,但他们的模拟采用的是零维模型,因此无法给出放电过程中各种粒子的产生和消失过程等信息,而这些特性对放电引发COIL是非常关键的。本文将采用流体力学和动力学混合模拟方法对放电引发脉冲COIL内的脉冲放电过程进行深入系统的研究。研究内容主要包括两部分,第一部分为CF3I-O2-O2(a1△g)-He混合气体脉冲放电性质的研究,即研究了放电过程中电压、电流特性,不同粒子密度的时空分布以及放电机制等。第二部分主要模拟研究了不同的放电参数(如电压、脉宽、气体配比等)对产生碘原子和激光效率的影响。研究结果期望为优化放电引发脉冲COIL实验装置,实现脉冲COIL的有效调控提供理论依据。模拟结果表明,CF3I-O2-O2(a1△g)-He混合气体脉冲放电中存在等离子体鞘层区和等离子体正柱区,因而具有明显的辉光放电特征。脉冲放电生成的碘原子主要来源是高能电子与CF3I的直接碰撞解离反应。此外,通过研究放电参数对碘原子密度的影响可以发现当外加电压幅值和脉冲宽度增加时,碘原子的密度会随之增加。在保持总气压和氧分压不变的情况下,CF3I和He存在一个最佳的配比,在此配比下,产生的碘原子密度最大并且产生单个碘原子所需的能量也最少。模拟结果还显示,碘原子的密度随总气压的升高而降低。在总压和氧压固定的情况下,当单重态氧的含量少于总氧含量的40%时,粒子数反转则不能形成,没有激光输出。
[Abstract]:Compared with CWCOILL, the pulsed oxygen-iodide chemical laser not only has the advantage of continuous wave oxygen-iodide chemical laser, but also has many unique advantages, for example, the laser can penetrate deeper depth and faster speed. The pulse laser with high energy can perform high efficiency Raman frequency shift, which makes the wavelength of the laser changeable and so on. As a result of these advantages, attracted the United States, Russia, China, Japan and many other countries to engage in scientific research. There are many methods to realize the pulse of oxygen-iodine chemical laser, among which the generation of iodine atom at the moment of pulse discharge is the most promising laser pulse technology. However, up to now, the related experimental studies are basically limited to the observation of external parameters under different conditions, and lack of research on the key link of producing pulsed laser, which makes people have certain blindness in the experiment. Compared with the experimental research work, the relevant theoretical simulation work is very few. In foreign countries, the only report seen at present is the work of Kochetov et al in recent years, but their simulation is based on zero dimensional model. Therefore, it is impossible to give the information about the generation and disappearance of various particles in the discharge process, and these characteristics are very important for the discharge initiation of COIL. In this paper, hydrodynamic and dynamic hybrid simulation methods are used to study the pulse discharge process in COIL. The first part is about the characteristics of CF3I-O2-O2(a1 g)-He mixed gas pulse discharge, that is, the characteristics of voltage, current, the space-time distribution of different particle density and the discharge mechanism. In the second part, the effects of different discharge parameters (such as voltage, pulse width, gas ratio, etc.) on the generation of iodine atoms and laser efficiency are studied. The results are expected to provide a theoretical basis for optimizing the experimental device of pulse COIL caused by discharge and realizing the effective regulation of pulse COIL. The simulation results show that the plasma sheath region and plasma positive column region exist in the mixed gas pulse discharge of CF3I-O _ 2-O _ 2O _ 2a _ 1 g)-He, so it has obvious glow discharge characteristics. The main source of iodine atoms generated by pulse discharge is the direct collision dissociation reaction between high energy electrons and CF3I. In addition, by studying the effect of discharge parameters on the density of iodine atoms, it can be found that the density of iodine atoms increases when the applied voltage amplitude and pulse width increase. Under the condition of keeping the total pressure and oxygen partial pressure constant, there is an optimum ratio of CF3I and he. Under this ratio, the density of iodine atom is the highest and the energy required to produce a single iodine atom is the least. The simulation results also show that the density of iodine atoms decreases with the increase of total pressure. In the case of fixed total pressure and oxygen pressure, when the content of singlet oxygen is less than 40% of the total oxygen content, the population inversion can not be formed and there is no laser output.
【学位授予单位】：大连理工大学
【学位级别】：硕士
【学位授予年份】：2015
【分类号】：TN248

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