等离子体

The vapour and plasma ignition times of the target are got based on the equation of heat conduction and cascade model. We suppose that the plasma is ignited when 210 generations of new electrons are born in vapour generation time. The influence of temperature on the thermodynamics and optics parameters of material also have been considered in the model. The resulting theory has good agreement with the experiment and overseas report. A blade method to measure the laser spot is given in this paper with validation and error analysis. The plasma threshold of metals in atmosphere and water ambients both are diagnosed with the light deflection and piezoelectric transducer. A Q-switched pulsed Nd:YAG laser operating at infrared (1064nm), visible(532nm) and ultraviolet (355nm) wavelengths has been used. Al、Fe、Cu are used as targets and get a similar results with both method. Theoretical and experimental analyses are applied on the influence of wavelength on the threshold have been done, both of which have shown that the plasma threshold of metals decrease as the laser wavelength increases; The plasma threshold of metals are higher in water than in air and the pressure of the shock wave in water is five times higher than in air.

从热传导方程和雪崩电离机制出发，假设当电子增值2~(10)倍时，考虑了温度对材料热力学和光学参数的影响时，得到了气化和等离子体点燃的时间，利用该模型进行计算得到的结果与国内外报道及自行通过实验测得的阈值基本一致；提出了利用刀刃法测量激光光斑面积的方法，并通过实验进行了验证和误差分析；利用光偏转装置和压电换能器分别对空气和水中金属等离子体点燃阈值进行了实验诊断，激光器均为调Q—YAG激光器(波长1064nm，532nm，355nm，脉宽10ns)，靶材分别为Al、Fe和Cu，两种测试方法得到的等离子体点燃阈值基本一致；本文从实验和理论计算两个方面讨论了波长对等离子体点燃阈值的影响，均得到了等离子体点燃阈值随着波长的增加而减小的结论；对空气中和水中不同环境下金属等离子体的点燃阈值进行了比较研究，得到了金属在水中的等离子体点燃阈值比空气中的大，且水中产生的冲击波的压强是空气中的5倍左右的结论。

BSpatial characterization of laser induced Cu plasma in air with different laser focusing distancesThe plasma spectra induced by pulsed laser ablation of copper target are measured. By adjusting the distance of the len-sample, the spectrum of air spark plasma、 Cu plasma and the reciprocity of both plasmas are analysed. From the result, it has been shown that the focusing of the laser beam has an important infunence to analyse the properties of the sample.

b 不同的激光焦点位置产生的等离子体光谱的空间特性研究激光烧蚀置于空气中的Cu靶产生等离子体，通过调节透镜与Cu靶的距离，本文观测了激光烧蚀空气产生的空气火花等离子体、激光直接烧蚀铜靶产生Cu等离子体以及空气火花等离子体与Cu等离子体相互作用等不同情况下的激光诱导击穿发射光谱，激光束焦点的位置在分析材料性质的过程中有着重要的影响。

Our main work is as follows: the stable laser mode theory in uniform plasmas is extended to non-uniform plasma cases; the discussion of the sufficient and necessary conditions for laser self-focusing in uniform plasmas is developed to non-uniform plasma cases; a quantitative approach to judge the impact of different plasma density distribution on laser self-focusing is proposed; the evolution properties of asymmetric laser filed in non-uniform and uniform plasmas are discussed and mechanisms that symmetric channel-like plasmas can confine the laser centroid around the plasma channel axes and symmetrize initially asymmetric laser beams are proposed; the formation of solitary standing wave in moderate plasma density is studied by PIC simulations and can be explained by stimulated Raman scattering of laser beams in plasmas.

主要工作为：把均匀等离子体中激光的稳定模理论推广到横向非均匀等离子体情形；把均匀等离子体中激光自聚焦的充分和必要条件的讨论推广到横向非均匀等离子体情形；给出横向密度分布不同的等离子体影响激光自聚焦的定量判据。讨论了初始不对称的激光场在横向非均匀及均匀等离子体中的演化特性，并提出了具有对称腔道结构的等离子体箍缩激光质心和对称化初始不对称激光场的物理机制。用粒子模拟讨论了激光场在等离子体中形成孤立驻波的过程，认为前向受激拉曼散射是发生此现象的可能机制。

The numerical results of the dispersion relation show some nonlinear effects: for a fixed geometry of a waveguid, beam parameters and plasma density, the increment of the modulation parameter may lead to a slight increment of the operating frequency, However, as the modulation parameter increases further, saturation may occur and the dispersion relations are hard to be separated, it is due to the overmodulation of the microwave power, this phenomenon itself belongs to the nonlinear effects.

五。用严格的场匹配方法分析了填充等离子体的耦合腔链，研究了等离子体一腔模的形成以及&冷&带宽和&热&带宽的展宽效应。等离子体填周期性耦合腔(来源：Aae53d3BC论文网www.abclunwen.com)链后，形成周期性的截止频率为0的等离子体TG模式。如果填充的等离子体密度较低时，腔模和槽模的工作频率均有小幅上升，而带宽改善不明显。

The phenomena of improved confinement has been observed with ECRH auxiliary heating under limiter discharge condition on the HL-2A tokamak, and electron line average density, plasma stored energy, radiated power within the separatrix, energy confinement time, H-alpha line emission etc, have been studied for the transition from L-mode to improved mode.

在HL-2A装置孔栏位形放电的等离子体实验中，电子回旋辅助加热期间观察到了等离子体约束改善的现象，并对等离子体从低约束模式向约束改善模式转换时的等离子体线平均电子密度、等离子体储能、分界面内辐射功率、能量约束时间、H辐射等进行了研究。

The statistic results showed that: Compared with the earward flow from the midtail, the nearEarth low latitude tailward flow from the ionosphere is characteristic of the lowtemperature and high density; With the tailward flow moving from the lobal region to the plasma sheet, the velocity of the tailward flow decrease, the density and the temperature increase. The tailward flow has distinct anisotropy depending on the difference of the parallel with perpendicular temperature.

对这516起尾向流的统计研究结果显示：（1）尾向流在从等离子体片边界层向等离子体片的运动过程中流速会逐渐减弱、密度逐渐增高，温度有逐渐下降的趋势；（2）对尾向流平行温度和垂直温度的分析显示不同等离子体区域的尾向流都有较明显的各向异性；（3）在从等离子体片边界层向等离子体片的运动过程中，尾向流逐渐趋向各向同性。

The third, since the electrons in the plasma are accelerated and ions move together, some harmful effects are also observed, such as both output powers of RBWO and FEL decrease versus the increase of plasma density. The results agree with the results of linear fluid model. In the unmagnetized plasma-loaded RBWO-FEL, output powers of pump source and FEL are obtained only in a narrow plasma density range and both have maximum. The results of simulation are in good agreement with the experimental results.

模拟分析了磁化等离子体填充的RBWO-FEL，尽管没有发现等离子体填充后RBWO及FEL输出功率的成倍增长，但是观察到等离子体的引入对RBWO-FEL产生以下影响：泵波及FEL的辐射频率的线宽得到明显增加；在较高的等离子体密度下，TM〓模将会被完全抑制；首次观察到T-G模振荡及功率输出，结果同线性理论计算结果基本一致；等离子体中的电子被加速及背景离子的移动将对器件工作产生不利影响。

The present dissertation deals with:(1) Exploring the feasibility of the CO〓 methanation and the conversion CH〓/H〓 into C〓 hydrocarbons under plasma with catalyst at ambient temperature and atmosphere.(2) Designing a reactor and preparing some catalysts suited for the conversion of carbon dioxide via the cooperation effect of plasma and catalysts.(3) Optimizing reaction conditions of conversion carbon dioxide to C〓 hydrocarbons in the proposed process.(4) Studying the reaction mechanism of conversion carbon dioxide to C〓 hydrocarbons under plasma by using in situ OES technology.(5) By the results of characterizing coked catalysts, exploring the reasons that result in the coking of catalyst and the paths for decreasing the deposit in the catalyst under plasma.(6) Analyzing the energy efficiency of the plasma catalysis and exploring the paths for improving the energy efficiency.

论文的主要研究工作包括：（1）探索脉冲电晕等离子体与催化剂共同作用CO〓／H〓甲烷化和由CH〓/H〓合成C〓烃反应的可行性；（2）研制等离子体催化CO〓转化的反应器和适配的催化剂；（3）优化等离子体催化CO〓转化制C〓烃反应的工艺条件和电参数；（4）利用原子发射光谱原位技术对等离子体反应的诊断结果，对等离子体催化CO〓转化制C〓烃反应的机理进行推断；（5）通过对积碳催化剂的表征结果，分析积碳的类型及其成因，并探讨减少积碳的途径；（6）通过对等离子体催化CO〓转化制C〓烃反应能量效率的分析，探讨提高等离子体催化反应能量效率的途径。

The plasma ignition threshold of metal is got through experimental and numerical study. The vapour and plasma ignition times of the target are got based on the equation of heat conduction and cascade model. We suppose that the plasma is ignited when generations of new electrons are born in vapour generation time. The influence of temperature on the thermodynamics and optics parameters of material also have been considered in the model. The resulting theory has good agreement with the experiment and overseas report. A blade method to measure the laser spot is given in this paper with validation and error analysis. The plasma threshold of metals in atmosphere and water ambients both are diagnosed with the light deflection and piezoelectric transducer. A Q-switched pulsed Nd:YAG laser operating at infrared (1064nm), visible(532nm) and ultraviolet (355nm) wavelengths has been used. Al、Fe、Cu are used as targets and get a similar results with both method. Theoretical and experimental analyses are applied on the influence of wavelength on the threshold have been done, both of which have shown that the plasma threshold of metals decrease as the laser wavelength increases; The plasma threshold of metals are higher in water than in air and the pressure of the shock wave in water is five times higher than in air .

从热传导方程和雪崩电离机制出发，假设当电子增值210倍时，考虑了温度对材料热力学和光学参数的影响时，得到了气化和等离子体点燃的时间，利用该模型进行计算得到的结果与国内外报道及自行通过实验测得的阈值基本一致；提出了利用刀刃法测量激光光斑面积的方法，并通过实验进行了验证和误差分析；利用光偏转装置和压电换能器分别对空气和水中金属等离子体点燃阈值进行了实验诊断，激光器均为调Q－YAG激光器（波长1064nm，532nm，355nm，脉宽10ns），靶材分别为Al、Fe和Cu，两种测试方法得到的等离子体点燃阈值基本一致；本文从实验和理论计算两个方面讨论了波长对等离子体点燃阈值的影响，均得到了等离子体点燃阈值随著波长的增加而减小的结论；对空气中和水中不同环境下金属等离子体的点燃阈值进行了比较研究，得到了金属在水中的等离子体点燃阈值比空气中的大，且水中产生的冲击波的压强是空气中的5倍左右的结论。

The influence rule to powder quality and quantity from some technical parameters such as materials vapor tension, gas pressure, the ratio between hydrogen and argon, current intensity and gas circulate intensity were discussed by single-factor experiment, on the base of which the perpendicularity experiment scheme was arranged.

本文采用压力模型计算出稳定弧光制粉时的气相空间温度在373K以下；从电流密度和电导率角度计算出等离子体电弧场中心温度高达5000-6500K；由此得出弱电离等离子体自由弧的自身温度场即使没有外界强制冷却，在等离子体焰区特征半径(约1.26cm)范围内的温度梯度就可达4787℃/cm，这是电弧等离子体温度场分布高度集中的具体表现，也是纳米金属粉末无须液氮冷却就能生成的本质原因，阐释了等离子体温度场自身的极大温度梯度是金属粉体纳米化的控制机制。

With Death guitarist Schuldiner adopting vocal duties, the band made a major impact on the scene.

随着死亡的吉他手Schuldiner接受主唱的职务，乐队在现实中树立了重要的影响。

But he could still end up breakfasting on Swiss-government issue muesli because all six are accused of nicking around 45 million pounds they should have paid to FIFA.

不过他最后仍有可能沦为瑞士政府&议事餐桌&上的一道早餐，因为这所有六个人都被指控把本应支付给国际足联的大约4500万英镑骗了个精光。