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1.
针对目前高速弹丸飞行参数测量系统采用被动光源存在的光源能量利用率低、对环境敏感等问题,研究了一种组合式主动激光阴影照相系统。在对系统理论分析的基础上建立了高速弹丸的空间位置模型和2种测速模型。搭建了激光阴影照相系统试验平台,对系统设计的合理性进行了检验。试验结果表明:2种测速模型都能实现对弹丸飞行速度的测量,并且2种方法的对比误差比较小;弹丸空间位置在X轴方向的均方差为0.795 mm,在Z轴方向的均方差为0.496 mm。与纸靶的测量结果相比,偏离程度在1 mm范围内;该系统能够实现对弹丸飞行参数的测量。 相似文献
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Béla Hopp Tomi Smausz Tamás Csizmadia Csaba Vass Csaba Tápai Bálint Kiss Martin Ehrhardt Pierre Lorenz Klaus Zimmer 《Applied Physics A: Materials Science & Processing》2013,113(2):291-296
Nanostructure formation on bulk noble metals (copper, gold and silver) by a femtosecond laser was studied aiming at the production of low-reflectivity surfaces. The target surface was irradiated with the beam of a 775 nm wavelength and 150 fs pulse duration Ti:sapphire laser. The fluence was in the 16–2000 mJ/cm2 range, while the average pulse number was varied between 10 and 1000 depending on the scanning speed of the sample stage. The reflectivity of the treated surfaces was measured with a visible–near-infrared microspectrometer in the 450–800 nm range, while the morphology was studied with a scanning electron microscope. A strong correlation was found between the decreasing reflectivity and the nanostructure formation on the irradiated surface; however, the morphology of silver significantly differed from those of copper and gold. For the two latter metals a dense coral-like structure was found probably as a result of cluster condensation in the ablation plume followed by diffusion-limited aggregation. In the case of silver the surface was covered by nanodroplets, which formation was probably influenced by the ‘spitting’ caused by ambient oxygen absorption in the molten silver followed by its fast release during the resolidification. 相似文献
4.
M. S. Grigoryeva I. N. Zavestovskaya A. P. Kanavin 《Bulletin of the Lebedev Physics Institute》2014,41(9):260-263
Empty pore collapse dynamics during laser annealing of metal surfaces is studied. A self-consistent model of pore radius variation in the melt is constructed. Pore size variation with the distance from the melting front is determined. 相似文献
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P. M. Ossi F. Neri N. Santo S. Trusso 《Applied Physics A: Materials Science & Processing》2011,104(3):829-837
Silver and gold thin films were deposited by pulsed laser ablation in a controlled Ar atmosphere at pressures between 10 and
100 Pa. Different morphologies, ranging from isolated nanoparticle arrays up to nanostructured thin films were observed. Fast
imaging of the plasma allowed deducing the expansion dynamics of the ablated plume. Plasma velocity and volume were used together
with the measured average ablated mass per pulse as input parameters in a model to estimate the average size of nanoparticles
grown in the plume. The nanoparticle size is expected to decrease from 4 nm down to 1 nm with decreasing Ar pressure between
100 and 10 Pa: this was confirmed by transmission electron micrographs which indicate a reduced dispersion of particle size
over narrow size ranges. The production of substrates for surface enhanced Raman scattering whose performances critically
depend on nanoparticle size, shape, and structure is discussed. 相似文献
6.
The mechanisms of material ablation and nanoparticle generation from metal samples exposed to intense short laser pulses are experimentally investigated. We performed measurements of the ablated volume using optical microscopy and the analysis of the ablation plume by fast imaging. The results confirm the existence of two distinguished ablation regimes as a function of the laser fluence, and give a deeper insight in the involved physical mechanisms. Thus, both regimes are found to be related to the relative amount of atoms and nanoparticles within the plume. Comparing the results obtained for copper and gold, it is possible to determine the influence of electron-lattice coupling on the sample heat regime and the resulting plume properties. 相似文献
7.
Z. Tóth B. Hopp Z. Kántor F. Ignácz T. Szörényi Z. Bor 《Applied Physics A: Materials Science & Processing》1995,60(5):431-436
The time course of laser light induced transport of tungsten films from a glass support is followed by ultrafast photography using delayed dye laser pulses. The photographs provide unambiguous evidence that the material transport in the 40–200 mJ/cm2 intensity domain takes place via removal of solid pieces from the film material. These results are consistent with heat flow calculations which predict the overall melting of the metal layer above 380 mJ/cm2. The series of photographs presented give detailed insight into the melting process and have revealed an unexpected in-flight phase separation of solid fracture pieces and molten droplets throughout the 200–900 mJ/cm2 domain. The faster propagating molten droplets form a condensed halo in front of the solid pieces, thereby providing an efficient shield between the processing laser light and the solid phase. 相似文献
8.
Experimental investigation of ablation efficiency and plasma expansion during femtosecond and nanosecond laser ablation of silicon 总被引:1,自引:0,他引:1
X. Zeng X.L. Mao R. Greif R.E. Russo 《Applied Physics A: Materials Science & Processing》2005,80(2):237-241
Femtosecond laser (Ti:sapphire, 100 fs pulse duration) ablation of silicon in air was compared with nanosecond laser (Nd:YAG, 3 ns pulse duration) ablation at ultraviolet wavelength (266 nm). Laser ablation efficiency was studied by measuring crater depth as a function of pulse number. For the same number of laser pulses, the fs-ablated crater was about two times deeper than the ns-crater. The temperature and electron number density of the laser-induced plasma were determined from spectroscopic measurements. The electron number density and temperature of fs-induced plasmas decreased faster than ns-induced plasmas due to different energy deposition mechanisms. Images of the laser-induced plasma were obtained with femtosecond time-resolved laser shadowgraph imaging. Plasma expansion in both the perpendicular and the lateral directions were compared. PACS 52.38.Mf; 52.30.-q 相似文献
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在激光能量130 mJ(靶面),脉宽60 fs,波长800 nm,对比度1∶10-6,激光与靶法线成45°夹角,P偏振,靶面激光峰值功率密度约为7.0×1017 W·cm-2,无预脉冲的条件下,采用电子谱仪与经γ标准源标定的LiF热释光探测器(TLD)相配合,测量了飞秒激光-薄膜靶相互作用中产生的超热电子能谱。根据所测的能谱,推算出超热电子的产额和激光能量转化为超热电子能量的效率,在靶法线方向分别为1.19×1010/sr和4.55%/sr,在激光反射方向分别为1.83×109/sr和0.76%/sr。结果显示,不同方向的超热电子产额和激光转化效率有所不同,原因在于激光-等离子体相互作用产生的超热电子构成各向异性的分布。 相似文献
10.
在激光能量130 mJ(靶面),脉宽60 fs,波长800 nm,对比度1∶10-6,激光与靶法线成45°夹角,P偏振,靶面激光峰值功率密度约为7.0×1017 W·cm-2,无预脉冲的条件下,采用电子谱仪与经γ标准源标定的LiF热释光探测器(TLD)相配合,测量了飞秒激光-薄膜靶相互作用中产生的超热电子能谱。根据所测的能谱,推算出超热电子的产额和激光能量转化为超热电子能量的效率,在靶法线方向分别为1.19×1010/sr和4.55%/sr,在激光反射方向分别为1.83×109/sr和0.76%/sr。结果显示,不同方向的超热电子产额和激光转化效率有所不同,原因在于激光-等离子体相互作用产生的超热电子构成各向异性的分布。 相似文献
11.
S.M. Huang M.H. Hong B. Lukiyanchuk T.C. Chong 《Applied Physics A: Materials Science & Processing》2003,77(2):293-296
Nanostructures on metal film surfaces have been written directly using a pulsed ultraviolet laser. The optical near-field
effects of the laser were investigated. Spherical silica particles (500–1000 nm in diameter) were placed on metal films. After
laser illumination with a single laser shot, nanoholes were obtained at the original position of the particles. The mechanism
for the formation of the nanostructure patterns was investigated and found to be the near-field optical resonance effect induced
by the particles on the surface. The size of the nanohole was studied as a function of laser fluence and silica particle size.
The experimental results show a good agreement with those of the relevant theoretical calculations of the near-field light
intensity distribution. The method of particle-enhanced laser irradiation allows the study of field enhancement effects as
well as its potentialapplications for nanolithography.
Received: 10 December 2002 / Accepted: 20 January 2003 / Published online: 28 May 2003
RID="*"
ID="*"Corresponding author. Fax: +65-777/1349, E-mail: HUANG_Sumei@dsi.a-star.edu.sg 相似文献
12.
L. Gallais E. Bergeret B. Wang M. Guerin E. Bènevent 《Applied Physics A: Materials Science & Processing》2014,115(1):177-188
For the development of organic electronics on flexible substrates, we study the potentialities of direct laser patterning of conductive films deposited on plastic foils. The materials under study are silver and platinum films (100-nm thick) deposited on Kapton® substrates. The experiments are done using a laser source operating at 1030 nm, 500 fs, under different irradiation conditions: single and multiple pulses at various frequencies. The laser ablation thresholds are measured and the ablation morphologies are analyzed with scanning electron microscopy. The results of these investigations show that photomechanical effects lead to delamination of the film and that depending of the irradiation conditions, incubation or heat accumulation effects can occur. The experimental results are compared to simulations based on the two-temperature model. Particularly we study the heat accumulation effects that can occur in the case of multiple pulses and that are detrimental for plastic substrates. 相似文献
13.
R Brako 《Solid State Communications》1983,47(7):559-561
Expressions for the trapping and sticking probability and for the energy accomodation coefficient of atoms on metal surfaces are derived by using a Gaussian form for the distribution of the energy transfer. The results are in good agreement with recent numerical simulation calculations and experiments. 相似文献
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We employ the particle-in-cell method to simulate the mechanisms of femtosecond (fs) laser interactions with a metallic target. The theoretical approach considers the solid as a gas of free electrons in a lattice of immobile ions and the laser fluences close to the ablation threshold. At first moments of the interaction, our simulations mapped out different nanostructures. We carefully characterized the rippling phase and found that its morphology is dependent on the distribution of the electron density and the period of the ripples depends on the laser intensity. The simulation method provides new insights into the mechanisms that are responsible for surface grating formation. 相似文献
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This paper describes a novel process of nanoparticle synthesis by pulsed laser ablation of consolidated microparticles. Metal microparticles, including Cu, Al and Ag, are consolidated by a cold isobaric press with pressures up to a few hundred MPa before laser irradiation. Nanoparticles are then synthesized in air by high-power pulsed laser ablation of the microparticles using a Q-switched Nd:YAG laser. It is shown that the degree of compaction plays a significant role in determining the size of the produced nanoparticles. The effect of laser fluence and collector position on the distribution of particle size is examined. Photoacoustic deflection probing and nanosecond time-resolved visualization indicate that the novel process attains increased efficiency of laser-energy coupling with the target. PACS 81.07.-b; 81.07.Wx; 42.62.Cf 相似文献
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The singlet-triplet conversion of the excited He(1s2s) metastable atom, approaching the metal surface with relatively low work function, is delt with on the basis of an extended Newns-Anderson model allowing the atom to have spin singlet and triplet states. After a canonical transformation, we show that a virtual process through the ionic states, of both the positive and the negative ions, makes the conversion possible. The numerical results show that in a certain range of parameters, the conversion possibly takes place in a region rather far from the surface. 相似文献
17.
The 3D atom probe(3DAP) is an imaging instrument based on the controlled field evaporation of single atoms from a sample having a tip shape with an end radius of 50 nm. In the fs laser assisted 3DAP the evaporation is induced by the laser pulses so that the physical process involved in this 3DAP analysis might correspond to the very early stages of the ablation process. In this paper we present the principle of the 3DAP and we discuss the existing models of the fs assisted evaporation. At last, we test the relevance of these models with pump-probe experiments on tungsten tips in the tomographic atom probe. 相似文献
18.
A route towards large area metal dot templates is presented. The templates are generated by diffraction mask projection laser ablation of thin metal films. The well ordered nanodot‐matrices are fast and easy to fabricate and show a high homogeneity over a large area. The metal nanodots are bound to the substrate, making them suitable for subsequent 3D nanostructure synthesis such as glancing angle deposition and nanowire growth mechanisms. (© 2008 WILEY‐VCH Verlag GmbH & Co. KGaA, Weinheim) 相似文献
19.
Polydiphenylsilylenemethylene (PDPhSM) thin films, which are difficult to fabricate by conventional methods because of their insolubility and high melting point, have been synthesized by using laser-ablated metal nanoparticles for the thermal ring-opening polymerization of 1,1,3,3-tetraphenyl-1,3-disilacyclobutane (TPDC) in this paper. TPDC was first evaporated on silicon substrates and then exposed to metal (Pt, Cu and Ag) nanoparticles deposition by laser ablation prior to heat treatment. The catalytic activity of Pt, Cu and Ag nanoparticles has been studied. The results showed that the mean diameter of Pt nanoparticles was the smallest, Cu nanoparticles the moderate and Ag nanoparticles the biggest, while the polymerization efficiency for Pt nanoparticles was the highest, Cu nanoparticles the moderate and Ag nanoparticles the lowest. In addition, the penetration behaviours of Pt, Cu and Ag nanoparticles into the TPDC monomer films during laser ablation were different due to the particle size or the chemical interaction between metal nanoparticles and TPDC molecules. 相似文献