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Effect of lens-to-sample distance on spatial uniformity and emission spectrum of flat-top laser-induced plasma

plasma Science and Technology 2022年第8期24卷 40-45页

作者：付洪波王华东张梦阳吴边张志荣 Anhui Provincial Key Laboratory of Photonic Devices and Materials Anhui Institute of Optics and Fine MechanicsHefei Institutes of Physical SciencesChinese Academy of SciencesHefei 230031People's Republic of China University of Science and Technology of China Hefei 230026People's Republic of China Key Lab of Environmental Optics&Technology Anhui Institute of Optics and Fine MechanicsHefei Institutes of Physical SciencesChinese Academy of SciencesHefei 230031People's Republic of China Advanced laser Technology Laboratory of Anhui Province Hefei 230037People's Republic of China

The optimal spectral excitation and acquisition scheme is explored by studying the effect of the lensto-sample distance(LTSD)on the spatial homogeneity and emission spectra of flat-top laser converging spot induced *** energy distribution characteristics before and after the convergence of the laser beam with quasi flat-top intensity profile used in this study are theoretically simulated and experimentally *** an aspheric converging mirror with a focal length of100 mm,the LTSD(106 mm≥LTSD≥96 mm)was changed by raising the stainless-steel sample *** plasma images acquired by ICCD show that there is air breakdown when the sample is below the focal point,and a ring-like plasma is produced when the sample is above the focal *** the sample is located near the focal point,the plasma shape resembles a *** the spectral acquisition region is confined to the plasma core and the image contains all the optical information of the plasma,it has a lower relative standard deviation(RSD)than the spectral *** the sample surface is slightly higher than the focal plane of the lens,the converging spot has a quasi flat-top distribution,the spatial distribution of the plasma is more uniform,and the spectral signal is more ***,there is little difference between the RSD of the plasma image and the laser *** order to further improve the stability of the spectral signal,it is necessary to expand the spectral acquisition area.

关键词： laser-induced plasma lens-to-sample distance plasma image RSD laser-induced breakdown spectroscopy

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Velocity Diagnosis of Critical Surface at Microwave Band in laser-induced plasma

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plasma Science and Technology 2008年第4期10卷 476-479页

作者：吴莹王俊彦白顺波陈建平楚然恽小华倪晓武 Applied Physics Department Nanjing University of Science and TechnologyNanjing 210094China Beijing Aeronautical Technology Research Center Beijing 100076China Microwave Center Nanjing University of Science and TechnologyNanjing 210094China

The velocity of critical surface at microwave band in laser-induced plasma was measured and the results are presented. The results indicate that the velocity of critical surface with low electron density is larger tha... 详细信息

关键词： laser-induced plasma microwave diagnosis Doppler effect

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Numerical Analysis of Interaction Between Single-Pulse laser-induced plasma and Bow Shock in a Supersonic Flow

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plasma Science and Technology 2012年第8期14卷 741-746页

作者：方娟洪延姬李倩 State Key Laboratory of laser propulsion&its application Academy of Equipment

The interaction of laser-induced plasma and bow shock over a blunt body is inves- tigated numerically in an M∞ =6.5 supersonic flow. A ray-tracing method is used for simulating the process of laser focusing. The gas located at the focused zone is ionized and broken down and transformed into plasma. In a supersonic flow the plasma moves downstream and begins to interact with the bow shock when it approaches the surface of the blunt body. The parameters of flowfield and blunt body surface are changed due to the interaction. By analyzing phenomena occurring in the complex unsteady flowfield during the interaction in detail, we can better under- stand the change of pressure on the blunt body surface and the mechanism of drag reduction by laser energy deposition. The results show that the bow shock is changed into an oblique shock due to the interaction of the laser-induced low-density zone with the bow shock, so the wave drag of the blunt body is reduced.

关键词： laser-induced plasma supersonic drag reduction bow shock flow character-istics

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Radio-frequency compressed electron pulse-width characterization by cross-correlation between electron bunches and laser-induced plasma

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Chinese Physics B 2014年第12期23卷 219-223页

作者：李静裴敏洁齐大龙齐迎朋杨岩孙真荣 State Key Laboratory of Precision Spectroscopy and Department of Physics East China Normal University

A method is proposed to determine the temporal width of high-brightness radio-frequency compressed electron pulses based on cross-correlation technique involving electron bunches and laser-induced plasma. The temporal evolution of 2-dimensional transverse profile of ultrafast electron bunches repelled by the formed transient electric field of laser-induced plasma on a silver needle is investigated, and the pulse-width can be obtained by analyzing these time-dependent *** approach can characterize radio-frequency compressed ultrafast electron bunches with picosecond or sub-picosecond timescale and up to 105 electron numbers.

关键词： radio-frequency compression electron pulse-width laser-induced plasma ultrafast electron diffraction

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Enhanced laser-induced plasma channels in air

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Chinese Physics B 2016年第3期25卷 256-261页

作者：左言磊魏晓峰周凯南曾小明粟敬钦焦志宏谢娜吴朝辉 laser Fusion Research Center China Academy of Engineering Physics Mianyang 621900 China Science and Technology on plasma Physics Laboratory Mianyang 621900 China IFSA Collaborative Innovation Center Shanghai Jiao Tong University Shanghai 200240 China

plasma is a significant medium in high-energy density physics since it can hardly be damaged. For some applications such as plasma based backward Raman amplification （BRA）, uniform high-density and large-scale plasma channels are required. In the previous experiment, the plasma transverse diameter and density are 50-200 μm and 1-2 x 10^19 cm-3, here we enhance them to 0.8 mm and 8 x 10^19 cm-3, respectively. Moreover, the gradient plasma is investigated in our experiment. A proper plasma gradient can be obtained with suitable pulse energy and delay. The experimental results are useful for plasma physics and nonlinear optics.

关键词： plasma channel laser-induced plasma plasma measurement plasma optics

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

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Frontiers of physics 2012年第6期7卷 649-669页

作者：俞进马千里 Vincent Motto-Ros 雷文奇王晓纯白雪石 Universite de Lyon F-69622 Lyon Universitd Lyon 1 Villeurbanne CNRS UMR5579 LASIM France

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 thermo-dynamic 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.

关键词： laser ablation laser-induced plasma plasma propagation plasma diagnostics plasmaemission laser-induced breakdown spectroscopy (LIBS)

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Terahertz generation from laser-induced plasma

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Opto-Electronic Science 2022年第8期1卷 41-67页

作者： Wenfeng Sun Xinke Wang Yan Zhang Department of Physics Capital Normal UniversityBeijing 100048China Beijing Key Lab of Metamaterials and Devices and Key Laboratory of Terahertz OptoelectronicsMinistry of EducationBeijing 100048China

Interest of the research in terahertz(THz)wave has been strongly motivated by its wide applications in the fields of physics,chemistry,biology,and *** efficient and reliable THz source is of uttermost priority in these *** attempts have been made in fulfilling the THz *** benefited from the progress of the ultrafast pulses,the laser-induced-plasma is one of the auspicious tools to provide desirable THz waves,owing to its superiorities in high power threshold,intense THz signal,and ultrawide THz *** paper reviews the physics and progress of the THz generation from the laser-induced plasmas,which are produced by gas,liquid,and *** characteristics of the emitted THz waves are also *** are many complicated physical processes involved in the interactions of laser-plasma,making various laser-plasma scenarios in the THz *** view of this,we will only focus on the THz generation classified by physical ***,we discuss a perspective on the future of THz generation from the laser-induced plasma,as well as its involved challenges.

关键词： terahertz generation ultrafast pulses laser-induced plasma

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Transmission effects of high energy nanosecond lasers in laser-induced air plasma under different pressures

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中国物理B:英文版 2023年第10期32卷 537-541页

作者：胡蔚敏尹凯欣王小军杨晶刘可彭钦军许祖彦 Key Laboratory of Solid State lasers Technical Institute of Physics and ChemistryChinese Academy of SciencesBeijing 100190China Institute of Optical Physics and Engineering Technology Qilu ZhongkeJinan 250000China University of Chinese Academy of Sciences Beijing 100049China

When a high energy nanosecond(ns)laser induces breakdown in the air,the plasma density generated in the rarefied atmosphere is much smaller than that at normal *** is associated with a relatively lower absorption coefficient and reduces energy loss of the laser beam at low *** this paper,the general transmission characterizations of a Joule level 10 ns 1064 nm focused laser beam are investigated both theoretically and experimentally under different *** evolution of the electron density(n_(e)),the changes in electron temperature(T_(e))and the variation of laser intensity(I)are employed for numerical analyses in the simulation *** experiments,four optical image transfer systems with focal length(f)of 200 mm are placed in a chamber and employed to focus the laser beam and produce plasmas at the *** results suggest that the transmittance increases obviously with the decreasing pressure and the plasma channels on the transmission path can be observed by the *** simulation results agree well with the experimental *** numerical model presents that the maximum n_e at the focus can reach 10^(19)cm^(-3),which is far below the critical density(n_(c)).As a result,the laser beam is not completely shielded by the plasmas.

关键词： laser-induced plasma high energy nanosecond laser pulse rarefied atmosphere

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Perspective of laser-induced plasma Ignition of Hydrocarbon Fuel in Scramjet Engine

Perspective of Laser-Induced Plasma Ignition of Hydrocarbon ...

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激光聚变能源检测与驱动技术研讨会

作者：杨雷超 Xiaohui Li Jianhan Liang Xin Yu Xipeng Li College of Aerospace Science and Engineering National University of Defense Technology National Key Laboratory of Science and Technology on Tunable laser Harbin Institute of Technology

laser-induced plasma ignition of an ethylene fuelled cavity was successfully conducted in a model scramjet engine *** ethylene was injected 10mm upstream of cavity flameholder from 3 orifices 60 degree inclined relative to freestream *** 1064nm laser beam,from a Q-switched Nd:YAG laser source running at 3Hz and 200mJ per pulse,was focused into cavity for *** speed photography was used to capture the transient ignition *** laser-induced gas breakdown,flame kernel generation and propagation were all recorded and ensuing stable supersonic combustion was established in *** flame kernel is found rotating anti-clockwise and gradually moves upwards as the entrainment of circulation flow in *** flame is then stretched from leading edge to trailing edge to fully fill the entire ***,a stable combustion is achieved roughly 900μs after the laser *** results show promising potentials for practical *** perspective of laser-induced plasma ignition of hydrocarbon fuel in scramjet engine is outlined.

关键词： laser-induced plasma Ignition Scramjet Engine

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Experimental Research on plasma induced by TEA CO_2 laser Propulsion

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plasma Science and Technology 2008年第2期10卷 203-206页

作者：卢宏程祖海左都罗翟冰洁余亮英朱海红 Division of laser Science and Technology Wuhan National Laboratory for Optoelectronics-Institution of Optoelectronics Science and Engineering Huazhong University of Science and Technology Wuhan 430074 China

Results in the air-breathing propulsion experiments with a parabolic light craft and a self-made UV-preionized 100 J TEA CO2 laser device are presented. Air disturbance and the spectrum of the plasma after the interaction of pulsed laser radiation with the light craft were studied. It was found that the focal length of the parabolic light craft had a significant effect on the air-disturbance. Two shock waves were detected for the longer focal length, while only one shock wave detected for the short focal length. The spectrum of the laser-induced plasma, the distribution of the characteristic lines, and the temporal behaviors of the air plasma were studied in detail. The results showed that, the evolution of the laser-induced plasma lasted 20μs, and the plasma spectrum would reach the maximum intensity at 7μs.

关键词： laser propulsion TEA CO2 laser-induced plasma air distribution

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