共查询到20条相似文献,搜索用时 46 毫秒
1.
Carlos A. Rinaldi Norberto G. Boggio Daniel Rodriguez Alberto LamagnaAlfredo Boselli Francisco ManzanoJorge Codnia M. Laura Azcárate 《Applied Surface Science》2011,257(6):2019-2023
Propulsion pellets of different metal/salt (Zn/CaCO3) composition have been prepared. The impulse imparted to the pellet by the laser has been measured using two different methods: a torsion pendulum and a piezoelectric sensor. The dependence of the coupling coefficient, Cm, on the composition of the solid binary propellants in ablative laser propulsion has been investigated under different experimental conditions: in vacuum and at atmospheric pressure as well as with two different wavelengths, IR and UV. The composition of the Zn/CaCO3 propellant mixture that optimizes the coupling coefficient, Cm, has been determined. 相似文献
2.
Yasir Jamil Humaima Saeed M. Raza Ahmad Shakeel Ahmad Khan Hashim Farooq Muhammad Shahid K. M. Zia Nasir Amin 《Applied Physics A: Materials Science & Processing》2013,110(1):207-210
Laser ablation propulsion is a form of beam-powered propulsion in which a pulsed laser ablates a target material thus producing thrust. We report in this work the measurements of various parameters related to laser-induced micropropulsion in toluene diisocyanate-based polyurethane polymer, aluminum and Co–Ni ferrite. The targets were irradiated by a Q-switched pulsed Nd–YAG laser at 1064 nm (pulse duration 5 ns) under atmospheric conditions. A contact-free optical triangulation method was used to measure the laser ablation induced thrust in the samples. The measurements and calculations depict that Co–Ni ferrite is better in terms of critical propulsion parameters C m and I sp. It has been observed that the propulsion parameters depend on the energy per pulse of the incident laser beam. 相似文献
3.
A comprehensive theoretical analysis of optimization of gain in CO2-N2 gasdynamic laser employing wedge or conical or hyperbolic nozzles with either H2O or He as the catalyst is presented. After a review of previous work, the usual governing equations for the steady inviscid
quasi-one-dimensional flow in a supersonic nozzle of a gasdynamic laser are used to obtain similar solutions for the various
flow quantities, which variables are subsequently used to optimize the small-signal gain on theP(20) line of the (001) → (100) transition of CO2 at wavelength 10.6μm. The corresponding optimum values like reservoir pressure and temperature and nozzle area ratio also have been predicted
and presented in the form of graphs. The analysis predicts that employing of 2D-wedge nozzle results in higher gain values and the CO2-N2-H2O gasdynamic laser employing 2D-wedge nozzle is operationally the best laser system for which the optimum value as high as 3.1 m−1 gain can be obtained. 相似文献
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We measured the momentum coupling coefficient Cm and laser-generated ion drift velocity and temperature in the femtosecond (fs) region, over a laser intensity range from ablation threshold to about one hundred times threshold. Targets were several pure metals and three organic compounds. The organic compounds were exothermic polymers specifically developed for the micro-laser plasma thruster, and two of these used “tuned absorbers” rather than carbon particles for laser absorption. The metals ranged from Li to W in atomic weight. We measured time of flight (TOF) profiles for ions. Specific impulse reached record values for this type of measurement and ablation efficiency was near 100%. These measurements extend the laser pulsewidth three orders of magnitude downward in pulsewidth relative to previous reports. Over this range, we found Cm to be essentially constant. Ion velocity ranged from 60 to 180 km/s. 相似文献
6.
《Journal of sound and vibration》1987,117(1):131-151
The longitudinal propagation of sound in quasi-one-dimensional low Mach number nozzle flow is considered in section 1. The solution in the ray approximation (section 2.1) is used to transform the wave equation into a Schrödinger form, which is studied for the family of power-law ducts, including, as a particular case, the conical nozzle. It is shown that the coincidence of flow sources/sinks with sound sources can lead to appearance of essential singularities (section 2.2), which can be removed by using a Riccati transformation (section 2.4). The exact solutions of the acoustic equations for the parabolic (Figure 1) and hyperbolic (Figure 2) nozzles are obtained in terms of Bessel functions (section 2.3), respectively of complex order and argument. The general formulas, together with limiting forms in the compactness, ray and asymptotic approximations (section 3.1), are used to establish properties of the acoustic velocity and pressure (section 3.2), kinetic and compression energies, and energy flux and wave action (section 3.3); for example, it is shown that the equipartition of energies for moderate variations in cross-section, gives way (Table 2) to a predominance of kinetic/compression energies respectively near blockages/openings. The effects of non-uniform mean flow (Table 1) are discussed by comparing horns with nozzles (section 3.4): e.g., it is shown that the duality principle, in three alternative forms, does not extend from horn to nozzles, and the acoustic equations have no elementary solutions for the latter, in contrast with the former. 相似文献
7.
Numerical simulation of air-breathing nanosecond laser propulsion considering subsonic inflow and multi-pulse 总被引:2,自引:0,他引:2
The model of paraboloid point focusing laser thruster is adopted to investigate numerically the air-breathing nanosecond laser propulsion under subsonic inflow and multi-pulse condition. The influence of pulse number and subsonic inflow on propulsive performance is analyzed. The simulation results indicate that the average impulse coupling coefficient Cmn decreases significantly with the increasing of pulse number because the air in the nozzle cannot recover to the initial state, but the trend becomes smooth due to the similar flow field before subsequent pulse. When the Mach number increases, the multi-pulse Cmn falls down at the same number of laser pulse. It shows that the faster subsonic inflow, the higher air drag and the shorter time of interaction between the shock wave and the thruster. 相似文献
8.
为了验证理论分析得到的圆锥形喷管在单脉冲条件下的激光推进能量相似律,用2维轴对称辐射流体动力学方法,计算得到了不同构形的推进性能参数,分析了锥角、长度、无量纲因子、入射激光能量对冲量、冲量耦合系数的影响。计算揭示的激光推进能量相似律合理,在理论模型可以描述的范围内,其定性规律与理论分析、实验结果之间相互印证。结果表明:当锥角固定时,冲量和冲量耦合系数随无量纲因子先增大后减小,极大值对应的无量纲因子仅与气体比热比相关;当无量纲因子固定时,冲量随入射激光能量增加而增大,冲量耦合系数受激光能量的影响很小,冲量和冲量耦合系数均随锥角增大而单调减小。 相似文献
9.
A.V. Simakin V.V. Voronov N.A. Kirichenko G.A. Shafeev 《Applied Physics A: Materials Science & Processing》2004,79(4-6):1127-1132
A review of results on nanoparticles formation is presented under laser ablation of Ag, Au, and Ti solids targets in liquid environments (H2O, C2H5OH, C2H4Cl2, etc.). X-ray diffractometry (XRD), UV-Vis optical transmission spectrometry, and high-resolution transmission electron microscopy (HRTEM) characterise the nanoparticles. The morphology of nanoparticles is studied as a function of both laser fluence and nature of the liquid. The evidence of an intermediate phase of Au-Ag alloy is presented under exposure of a mixture of individual nanoparticles to laser radiation. Self-influence of the beam of a femtosecond laser is discussed under the ablation of the Ag target in liquids under Ti:sapphire laser. The factors are discussed that determine the distribution function of particle size under laser ablation. The influence of laser parameters as well as the nature on the liquid on the properties of nanoparticles is elucidated. PACS 42.62.-b; 61.46.+w; 78.66.-w 相似文献
10.
G. Dominiak-Dzik W. Ryba-Romanowski R. Lisiecki P. Solarz M. Berkowski 《Applied physics. B, Lasers and optics》2010,99(1-2):285-297
Spectroscopic and kinetics properties of Lu2SiO5:Dy3+ (LSO:Dy) single crystal with 1 and 5 at.% of activator were investigated. The polarised absorption and unpolarised emission spectra were measured at 10–300 K. Parameters characterising radiative relaxations of LSO:Dy were estimated by the Judd–Ofelt model. The crystal-field energy structure was derived from low-temperature optical spectra exhibiting the presence of two non-equivalent Dy3+ sites. It was found that dysprosium ions in site 1 and in site 2 do not form isolated subsystems; these subsystems are coupled by an effective spectral energy migration process. The LSO:Dy crystal exhibits a strong luminescence in the visible. Strong ion–ion interactions were observed for LSO:Dy (5 at.%); luminescence decays are non-exponential and the macro-parameter of donor–acceptor interaction C da amounts to 5.3 (10?52 m6?s?1) and 7.8 (10?52 m6?s?1) at 10 and 300 K, respectively. Laser potential related to the 4F9/2→6H13/2 yellow luminescence in Dy:LSO was assessed based on evaluation of the emission cross section values. It was concluded that the crystal is a promising material for visible laser operation. 相似文献
11.
The deposition of carbon nanotubes and carbon nano-onions at room temperature using excimer laser radiation to ablate mixed graphite-metal targets is described. Our deposition conditions are in contrast to other investigations on the pulsed laser deposition of carbon nanotubes that have employed high temperatures and high pressures. We find that the formation of these carbon nanostructures is dependent on the ambient gas employed during ablation. In the presence of O2 gas, carbon nanotubes and nano-onions are produced, while inert atmospheres such as Ar yield amorphous carbon. High-resolution, in situ, time-resolved emission spectroscopy has been used to track the evolution of species (C2, C3, Ni/Co) in the ablation plume. Spectral fits on low and high-resolution spectra reveal that the vibrational-rotational temperatures for C2 produced in O2 remain at ∼5000 K for nearly 20 μs but drop rapidly in Ar. Details of the formation of carbon nanotubes and nano-onions, and in situ time-resolved optical emission spectroscopy are described. 相似文献
12.
为了验证理论分析得到的圆锥形喷管在单脉冲条件下的激光推进能量相似律,用2维轴对称辐射流体动力学方法,计算得到了不同构形的推进性能参数,分析了锥角、长度、无量纲因子、入射激光能量对冲量、冲量耦合系数的影响。计算揭示的激光推进能量相似律合理,在理论模型可以描述的范围内,其定性规律与理论分析、实验结果之间相互印证。结果表明:当锥角固定时,冲量和冲量耦合系数随无量纲因子先增大后减小,极大值对应的无量纲因子仅与气体比热比相关;当无量纲因子固定时,冲量随入射激光能量增加而增大,冲量耦合系数受激光能量的影响很小,冲量和冲量耦合系数均随锥角增大而单调减小。 相似文献
13.
Cui C. Y. Hong Y. J. Ye J. F. Wen M. Li N. L. 《Applied Physics A: Materials Science & Processing》2011,102(1):239-243
Time-resolved force sensing and intensified charge-coupled device (ICCD) imaging techniques were applied to the study of the
effects of laser energy density on impulse coupling coefficient of laser ablation of water for propulsion. A Transversely
Excited at Atmospheric pressure (TEA) CO2 laser operated at 10.6 μm, 30 J pulse energy was used to ablate water contained in a quadrate quartz container. Net imparted
impulse and coupling coefficients were derived from the force sensor data and relevant results were presented for various
laser energy densities. ICCD imaging was used in conjunction with the dynamic force techniques to examine the dependencies
on laser energy density. Results showed that the impulse coupling coefficient could reach a maximum value when laser energy
density was about 105 J/m2, and it would increase before laser energy got to this point and would decrease after this point, and ICCD imaging supplied
important phenomenon to explain this variation, which were water ablation before laser energy density got to 105 J/m2 and laser-induced air-breakdown with water as an induction when laser energy density was higher than 105 J/m2. 相似文献
14.
We have observed several kinds of hydrocarbon cations after the nanosecond and the femtosecond laser ablation (nsLA and fsLA) of solid C60. The observation indicates that the carbon fragments produced just after laser ablation of the C60 molecule react with the hydrogen atoms and ions coexisting in the ablation plume. In the case of fsLA, clear dependence of the product hydrocarbon species on the ablation laser power has been observed although the dependence is not clearly observed in nsLA. The production of CnH5+ (n = 8, 10, and 12) is only observed in fsLA suggesting the unique nature of the transient carbon fragments produced by fsLA. 相似文献
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Y. Okada Y. Kuga K. Sunouchi S. Satooka S. Isomura A. Suda A. Tsunemi H. Tashiro K. Takeuchi 《Applied physics. B, Lasers and optics》1994,59(4):475-477
Measurements of multiphoton absorption of 16 µm Raman-laser radiation in supercooled238UF6 at 90 K were performed by using a pulsed Laval nozzle with an optical path length of 50 cm. The laser fluence was varied between 50 and 500 mJ/cm2 for four frequencies in the range from 625 to 629 cm–1. The energy absorbed by238UF6 molecules was investigated as a function of laser frequency or fluence, and highly accurate results were obtained with the use of the nozzle whose optical path length is much greater than that of nozzles used before. The results indicated that the absorption cross section at the peak absorption frequency (627.8cm–1) was proportional to the –1/3 power of the fluence. 相似文献
18.
Loktionov E. Yu. Ovchinnikov A. V. Protasov Yu. S. Protasov Yu. Yu. Sitnikov D. S. 《Optics and Spectroscopy》2012,112(4):631-637
The opto-mechanical characteristics, such as the specific mechanical recoil momentum, the specific impulse, and the energy
efficiency, of the laser ablation of flat polymer targets ((C2F4)
n
, (CH2O)
n
) have been determined experimentally for the first time for the case of excitation with femtosecond pulses (τ ∼ 45–70 fs)
of UV-IR (λ ∼ 266, 400, 800 nm) laser radiation (I
0 up to 1015 W/cm2) under normal atmospheric and vacuum (p ∼ 10−4 mbar) conditions. The efficiency of mechanical recoil momentum generation is analyzed for various regimes of the laser irradiation. 相似文献
19.
R. Mahfouz F. J. Cadete Santos Aires A. Brenier E. Ehret M. Roumié B. Nsouli B. Jacquier J. C. Bertolini 《Journal of nanoparticle research》2010,12(8):3123-3136
A YAG laser operating at the second harmonic wavelength (532 nm, 10 Hz, 8 ns and 40 mJ) was used to elaborate bimetallic nanoparticles by laser ablation of Ni75Pd25 and Au75Ag25 targets in water. TEM–EDX, UV–Vis spectroscopy and PIXE measurements were performed to obtain information on their mean sizes, size distributions and chemical composition as a function of the time of laser ablation. The surface of the laser impacted regions of the targets were characterized by RBS in order to check their composition after the laser ablation. The so-obtained bimetallic nanoparticles always show a homogeneous composition. However, while the composition of Au–Ag nanoparticles was found to be very similar to the one of the alloy target, the composition of the Ni–Pd nanoparticles can be different from the nominal composition of the alloy target. Segregation phenomena can be invoked to explain the difference between the Ni–Pd nanoparticles and the Au–Ag nanoparticles compositions obtained in the same conditions. However, an influence of chemical reactions occurring in the high pressure plasma created locally at liquid–solid interface (called ‘reactive quenching’) cannot be completely ruled out. 相似文献
20.
The interrupting capability of a gas-blast high-voltage circuit breaker (CB) is mainly determined by the self-induced pressure rise caused by the thermal arc energy, the composition of the arc plasma and the chemical reactions occuring during and after current interruption. We have studied the nozzle materials boron nitride (BN), quartz (SiO2), polytetrafluoroethylene (PTFE), ethylene-tetrafluoroethylene (ETFE), polyethylene (PE) and epoxy resin (ER) with respect to their influence on these processes with the aid of a model circuit breaker (MCB). Direct measurements of the arc-induced pressure rise reveal that the portion of the arc energy available for the pressure rise varies greatly (20%–65%) with the properties of the nozzle material. Nozzle erosion is significantly higher for materials with high values (e.g. polymers). Therefore, the lifetime of polymer nozzles is considerably shorter than that of ceramic nozzles. We have investigated the influence of the nozzle material on the decomposition products formed in the arc discharge of our MCB by studying the composition and time dependence of these products. The MCB was directly attached to the time-of-flight mass spectrometer (TOFMS) with the aid of a molecular-beam sampling system, which allowed real-time measurements of the arced gas during and after current interruption, thus providing information on the ablation mechanism and on the reaction kinetics of vaporised nozzle material with dissociated SF6. The most abundant long-lived reaction products are SF4, SOF2, C2H2, CO, and CS2. Their formation rates have been determined as functions of the nozzle material. With respect to quantities and properties of decomposition products, ceramics are superior to polymers since they form only small concentrations of corrosive and toxic products. 相似文献