Generation and expansion of laser-induced plasma as a spectroscopic emission source

Laser-induced plasma represents today a widespread spectroscopic emission source. It can be easily generated using compact and reliable nanosecond pulsed laser on a large variety of materials. Its application for spectrochemical analysis for example with laser-induced breakdown spectroscopy (LIBS) has become so popular that one tends to forget the complex physical and chemical processes leading to its generation and governing its evolution. The purpose of this review article is to summarize the backgrounds necessary to understand and describe the laser-induced plasma from its generation to its expansion into the ambient gas. The objective is not to go into the details of each process; there are numerous specialized papers and books for that in the literature. The goal here is to gather in a same paper the essential understanding elements needed to describe laser-induced plasma as results from a complex process. These elements can be dispersed in several related but independent fields such as laser-matter interaction, laser ablation of material, optical and thermodynamic properties of hot and ionized gas, or plasma propagation in a background gas. We believe that presenting the ensemble of understanding elements of laser-induced plasma in a comprehensive way and in limited pages of this paper will be helpful for further development and optimized use of the LIBS technique. Experimental results obtained in our laboratory are used to illustrate the studied physical processes each time such illustration becomes possible and helpful.     

等离子体通道的声学诊断方法

超短脉冲强激光在空气中传输可以形成很长的等离子体通道，目前对这种等离子体通道有许多诊断方法，文章介绍了一种十分简易但很有效的方法——声学测量方法．该方法可以根据通道不同位置的声音信号，测量通道的长度和通道内电子密度等一些参数，具有其他传统诊断方法无可比拟的优越性．     

注入剂量和低温退火对硅离子注入热氧化硅层发光特性的影响

采用金属蒸气真空弧(MEVVA)离子源制得了SiO2:Si辐照层。样品的室温可见PL谱峰位集中在560～700nm的4个谱带;Raman谱表明样品中没有纳米硅晶形成,XPS谱检测到富氧和缺氧两种价键结构。560nm发光中心起源于氧化硅层中的富氧结构缺陷SPR,620～700nm的谱峰均源自非桥氧空穴中心NBO     

Acoustic Diagnostics of Plasma Channels Induced by Intense Femtosecond Laser Pulses in Air

Long plasma channels induced by femtosecond laser pulses in air are diagnosed using the sonographic method. By detecting the sound signals along the channels, the length and the electron density of the channels are measured. Refocusing is also observed at different laser energies and different focal lengths. We find that the sonographic method has manifest advantages compared to other techniques.     

双金属复合钢管界面及焊缝的微观结构

通过金相分析、微区成份分析、宏观和微观断口分析,主要研究钎焊层和焊缝区的微观结构及其对复合钢管工艺性能和使用性能的影响。研究结果表明,镍基钎焊层通过扩散形成界面,实现了完全的冶金结合。组成复合钢管的各层以及焊缝金属的力学性能相近,变形均匀,保证了复合钢管的可焊性和强韧性。铜钎焊复合钢管由于高温铜脆而引发焊接裂纹,且其钎焊层硬度明显高于基层和复层,导致层间剪切及沿界面发生分层脱离,固该铜基合金不宜做复合钢管钎焊料。